JP2009282610A - Information distribution system, distribution server in same system and storage method for content information in same distribution server - Google Patents

Abstract

An information distribution system including a distributed server system capable of ensuring that all content information input to the information distribution system can be distributed, a distribution server in the system, and a method of storing content information in the distribution server are provided. .
Non-permanent retention that is not prohibited from being deleted from content information stored in a storage means when the storage means does not have a storage area for storing new permanent retention content information acquired from another device The content information is deleted to secure a storage area, and the new permanently retained content information acquired from another device is stored in the secured storage area.
[Selection] Figure 10

Description

  The present invention relates to an information distribution system, a distribution server in the system, and a content information storage method in the distribution server.

  Conventionally, a plurality of terminal devices are connected via an information communication line such as the Internet to construct an overlay network capable of bidirectional information communication between the terminal devices, and storage (storage means) in each terminal device. ), An information distribution system in which a huge storage composed of storage groups of a plurality of terminal devices is virtually constructed by storing various pieces of content information (see, for example, Patent Document 1). ).

  In this type of information distribution system, in order to ensure that all content information input to the system can be distributed, each content information is stored in at least one terminal device participating in the information distribution system. Need to be.

  However, as described above, in this information distribution system, since the virtual storage is configured by a storage group of a plurality of terminal devices, if any terminal device withdraws from the network of the information distribution system at an arbitrary timing, the withdrawal is performed. If there is content information stored only in the terminal device, there is a problem that it is impossible to completely guarantee all content information input to the information distribution system.

  Moreover, even if the content information is popular, if there are few terminal devices that hold the content information, the content information cannot be sufficiently distributed between the terminal devices depending on the distribution capability of the terminal device. It is not possible to completely guarantee all content information input to the system.

  Therefore, in addition to the distributed storage by the terminal device, an information distribution system is devised that stores all the content information input to the information distribution system and has a distribution server that can distribute the content information in response to a request from the terminal device. ing.

  However, if it is attempted to distribute all the content information input to the information distribution system with a single distribution server in this way, there is a possibility that the equipment cost for that will increase significantly.

  In other words, in order to guarantee an enormous amount of content information with a single server, a high-performance and expensive server equipped with a large-scale storage is required, and it is possible to cope with maintenance and failure of this server. Therefore, a backup distribution server having performance equivalent to that of this distribution server is also required, and there is a problem that the equipment cost for constructing the information distribution system is greatly increased.

  In order to solve such a problem, an information distribution system is constructed by using a distributed server system in which all content information is not stored in one distribution server but is distributed and stored in a plurality of distribution servers. Can be considered.

By constructing the information distribution system using the distributed server system in this way, even if the content information to be input to the information distribution system increases, the content information can be increased only by adding a relatively inexpensive server device. Since this can be dealt with, it is possible to suppress a significant increase in the cost required for the equipment.
JP 2006-197400 A

  In the distributed server system, even if one distribution server fails, the same content information is repeatedly stored in a plurality of distribution servers so that all the content information input to the information distribution system can be guaranteed. It is desirable to keep it. In particular, for popular content information, when there are few terminal devices that hold the content information, there are many requests for distribution from the terminal devices, so the number of content information held by a plurality of distribution servers should be increased. Is desirable.

  However, if a large number of identical content information is stored in a plurality of distribution servers, the greater the number of duplicates, the more storage capacity in the distributed server system will be compressed. Content information may not be added.

  In addition, if content information stored in the distribution server is deleted in an attempt to secure a storage area for adding new content information, some content information does not exist in the distributed server system and is input to the information distribution system. There is a risk that it is difficult to guarantee all the content information.

  Therefore, the present invention provides an information distribution system including a distributed server system capable of ensuring that all content information input to the information distribution system can be distributed, a distribution server in the system, and a method of storing content information in the distribution server The purpose is to provide.

  In order to achieve this object, the invention according to claim 1 is an information distribution system comprising a plurality of distribution servers that hold a plurality of pieces of content information and transmit content information in response to a request from a terminal device. In the distribution server, storage means for storing the content information, acquisition means for acquiring together with information on whether or not to delete the content information from another device, and whether or not to delete the content information acquired from the other device Storage processing means for storing in the storage means together with the information of the storage means, the storage processing means when the storage means does not have a storage area for storing content information acquired from the other device The content information that is not prohibited to be deleted is secured from the content information stored in the storage area, and the storage area is secured. And to store the acquired content information from the other device to pass.

  The invention according to claim 2 is the invention according to claim 1, wherein when the content information transmission request is received from the terminal device, the content information corresponding to the transmission request is stored in the storage means. Determination means for determining whether or not the content information determined to be stored in the storage means by the determination means is transmitted to the terminal device that has made the transmission request, and the acquisition means includes: The content information determined not to be stored in the storage means by the determination means is acquired together with information indicating whether or not deletion is prohibited from another distribution server, and the transmission means acquires the content information acquired from the other distribution server. , And transmitting to the terminal device that made the transmission request.

  In the invention according to claim 3, in the invention according to claim 2, a storage area for storing content information corresponding to a transmission request from the terminal device cannot be secured by the storage processing means. Transmission request means for requesting the content information corresponding to the transmission request to be transmitted to the other delivery server storing the content information corresponding to the transmission request to the terminal device that has made the transmission request. It is provided with.

  According to a fourth aspect of the present invention, in the third aspect of the present invention, the transmission requesting unit includes a storage area for storing content information acquired from the other distribution server by the storage processing unit. When it cannot be secured in the storage means, it requests the other distribution server storing the content information corresponding to the transmission request to transmit to the other distribution server not storing the content. It is characterized by.

  Further, the invention according to claim 5 is the invention according to any one of claims 1 to 4, wherein the free capacity acquisition means for acquiring the free capacity of the storage means of the plurality of distribution servers, When a content information addition request is received from a device, a distribution server for storing content information corresponding to the addition request is determined according to the free capacity of the storage means of the plurality of distribution servers acquired by the free capacity acquisition means And an addition processing means for storing content information corresponding to the addition request in the distribution server determined by the determination means.

  The invention according to claim 6 is the invention according to claim 5, wherein the determining means stores a distribution server for storing content information in response to the addition request among the plurality of distribution servers. A predetermined number is selected in order from the distribution server having the largest available capacity of the means.

  Further, the invention according to claim 7 is the invention according to any one of claims 1 to 6, wherein the storage processing means is a P2P formed by a plurality of the terminal devices as the content information to be deleted. The content information stored in the network in a predetermined number or more is selected.

  The invention according to claim 8 is the invention according to any one of claims 1 to 6, wherein the storage processing means stores the predetermined number or more of the plurality of distribution servers as the content information to be deleted. The content information is selected.

  The invention described in claim 9 is a program that causes a computer to function as each means of the distribution server described in any one of claims 1 to 8.

  The invention according to claim 10 is an information distribution system comprising a plurality of distribution servers that hold a plurality of pieces of content information and transmit content information in response to a request from a terminal device. Storage means for storing the content information; acquisition means for acquiring content information from another device together with information indicating whether deletion is prohibited; and information about whether content information acquired from the other device is prohibited from being deleted Storage processing means for storing in the storage means, and the storage processing means stores in the storage means when there is no storage area for storing content information acquired from the other device. Content information that is not prohibited from being deleted is secured to secure a storage area, and the other storage device is stored in the secured storage area. And to store the acquired content information.

  According to the eleventh aspect of the present invention, there is provided a storage method of the content information in a distribution server that stores a plurality of pieces of content information in a storage unit, and extracts and transmits content information corresponding to a request from a terminal device from the storage unit. A storage area for storing content information acquired from the other device by the storage processing means, and a step of acquiring the content information from the other device together with information indicating whether or not deletion is prohibited. Content information stored in the storage means, content information that is not prohibited to be deleted is deleted to secure a storage area, and content information acquired from another device in the reserved storage area Storing the information together with information indicating whether or not deletion is prohibited.

  According to the present invention, the distribution server acquires content information from another device together with information indicating whether or not deletion is prohibited, stores the acquired content information together with information about whether or not deletion is prohibited, and then stores the content information in the storage unit. When the storage means does not have a storage area for storing content information acquired from another device, delete the content information that is not prohibited from being deleted from the content information stored in the storage means. Content information acquired from another device is stored in the reserved storage area together with information indicating whether or not deletion is prohibited, so that content information together with information indicating deletion prohibition is stored in at least one distribution server among a plurality of distribution servers. All content information input to the information distribution system is held in a distributed storage consisting of multiple distribution servers. It is. As a result, it is possible to ensure that all content information input to the information distribution system can be distributed.

  Hereinafter, several embodiments of the information distribution system S of the present invention will be described with reference to the drawings.

[1. Configuration of information distribution system S]
First, an outline of an information distribution system according to an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a diagram illustrating an example of a connection mode of each terminal device, each distribution server, and a center server in the information distribution system according to the present embodiment. FIGS. 2 and 3 illustrate content information from the distribution server in the distributed content pool. It is a figure which shows a mode that it acquires.

  As shown in the lower frame 51 of FIG. 1, IX (Internet eXchange) 3, ISP (Internet Service Provider) 4, DSL (Digital Subscriber Line) line provider (device) 5, FTTH (Fiber To The Home) line A network (real-world network) 8 such as the Internet is constructed by an operator (device) 6 and a communication line (for example, a telephone line or an optical cable) 7.

  As shown in the upper frame 50 of FIG. 1, the information distribution system S includes a plurality of distribution servers 1a, 1b, 1c, 1d and a plurality of terminal devices 2a, 2b, 2c connected to each other via a network 8. , 2x, 2y, 2z,... And the center server 10. These devices are assigned a unique manufacturing number (for example, a MAC address) and an IP (Internet Protocol) address as information indicating each device. Note that the serial number and IP address are not duplicated among a plurality of apparatuses. In the following description, when any one of the distribution servers 1a, 1b, 1c, and 1d or all distribution servers are indicated, the distribution server 1 may be referred to for convenience. In addition, when any one of the terminal devices 2a, 2b, 2c... 2x, 2y, 2z.

  In the information distribution system S of the present embodiment, overlay networks 9a and 9b are constructed as shown in the upper frame 50 of FIG. That is, the overlay networks 9a and 9b mean networks that constitute virtual links formed using the existing network 8. The overlay network 9a is formed from a plurality of distribution servers 1a, 1b, 1c, and 1d, and is an overlay network that distributes content information in response to a request from the terminal device 2 (hereinafter referred to as “distributed content pool 9a”). ). The overlay network 9b is formed of a plurality of terminal devices 2a, 2b, 2c... 2x, 2y, 2z..., And is a peer-to-peer (P2P) type overlay network (hereinafter, “content sharing network 9b”). It is called). Hereinafter, the distribution server 1 arranged on the overlay network 9a is referred to as the distribution server 1 participating in the distributed content pool 9a, and the terminal device 2 arranged on the content sharing network 9b is referred to as the content sharing network 9b. The terminal device 2 participating in the system.

  If the terminal device 2 of the content sharing network 9b does not find the desired content information (hereinafter referred to as “content information A”) in the network 9b, the content is transmitted from the distribution server 1 of the distributed content pool 9a. Information A is acquired. The location information (IP address, etc.) of the distribution server 1 necessary for accessing the distribution server 1 from the terminal device 2 is a list of content information (hereinafter referred to as “content catalog”) acquired by each terminal device 2 from the center server 10. To get from). That is, the content catalog includes information for acquiring content information input to the information distribution system S from the distribution server 1 by the terminal device 2. When the terminal device 2 intends to acquire content information from the distribution server 1, the terminal device 2 selects any one distribution server 1 from among the plurality of distribution servers 1, and stores the location information of the distribution server 1 thus selected as a content catalog. Get from.

  In FIG. 2, when the terminal device 2a cannot find the desired content information (here, content information A) in the content sharing network 9b (see (1) shown in FIG. 2), the distributed content pool. The content information A is acquired from the distribution server 1a of 9a (see (2) shown in FIG. 2). That is, the content list includes location information (such as an IP address) of each distribution server 1 for acquiring content information input to the information distribution system S from the distribution server 1, and the terminal device 2a A transmission request for content information A is made to the randomly selected distribution server 1a. Then, the distribution server 1a transmits the content information A stored in the content storage area of the storage means to the terminal device 2a (see (3) shown in FIG. 2).

  Here, the plurality of pieces of content information held in the distributed content pool 9a are distributed and arranged in the content storage areas of the storage means of the plurality of distribution servers 1. Therefore, the distribution server 1a may not hold the content information A that has received a transmission request from the terminal device 2a.

  In this case, the distribution server 1a requests the content information A requested from the terminal device 2a to the other distribution server 1b (see (3) shown in FIG. 3), and acquires the content information A from the distribution server 1b. (Refer to (4) shown in FIG. 3). Then, the distribution server 1a transmits the content information A acquired from the distribution server 1b to the terminal device 2a (see (5) shown in FIG. 3).

  At this time, the distribution server 1a stores the content information A acquired from the distribution server 1b in the content storage area of the storage unit of the own device. Thereby, when there is a transmission request of the content information A from the terminal device 2 thereafter, the content information A is taken out from the content storage area of the storage means of the own device without making a transmission request to the other distribution server 1, It can be transmitted to the terminal device 2.

  Therefore, content information that is popular content information and that is difficult to be transmitted and received between the terminal devices 2 is held in a number of distribution servers 1. In this way, the distribution server 1 acquires the content information (hereinafter also referred to as “replica”) from the other distribution server 1 when the content information requested for transmission from the terminal device 2 is not held. ing.

  This replica increases every time there is a request for content information to the distribution server 1 that does not hold the content information requested from the terminal device 2. Therefore, many replicas are created in the distributed content pool 9a, and it becomes possible to quickly respond to a content transmission request from the terminal device 2.

  However, the greater the number of replicas held in the plurality of distribution servers 1, the more storage capacity in the distributed content pool 9a is compressed. As a result, new content information may not be added. Further, if the content information stored in the distribution server 1 is deleted in order to secure a storage area for newly adding content information, a part of the content information does not exist in the distributed content pool 9a, and the information distribution system There is a possibility that it is difficult to guarantee all the content information input to S.

  Therefore, it is conceivable to provide a management server for managing the content information held by each distribution server 1 to prevent the necessary content information from being deleted from the distribution server 1. However, if this is done, if a failure occurs in the management server, the function of the distributed content pool 9a will fail. In addition, since a separate management server is required in addition to the distribution server 1, the cost is increased.

  Therefore, in the distributed content pool 9a according to the present embodiment, each distribution server 1 determines whether there is no problem even if the held content information is deleted, and deletes unnecessary content information when adding new content information. Therefore, the storage area is secured and content information is added.

  In this way, content information can be retained by efficiently using the content storage area of the storage unit in the distribution server 1 while ensuring that the content information always exists in the distributed content pool 9a. it can.

[2. Overview of Distributed Content Pool 9a]
Hereinafter, an outline operation in the distributed content pool 9a will be described with reference to the drawings. FIG. 4 is a diagram showing how content information is added to the distribution server 1 in the distributed content pool 9a, and FIG. 5 is a diagram showing how the terminal device 2 acquires content information from the distribution server 1 in the distributed content pool 9a. 6 is a diagram showing the state of the content storage area of the storage means of the distribution server 1, FIG. 7 is a diagram showing the state of the content storage area of the storage means of each distribution server 1, and FIG. 8 is a free capacity list held by the distribution server 1 FIG. 9 and FIGS. 11 to 14 are diagrams for explaining the determination method of the distribution server 1 for holding the new content information, and FIG. 10 is a diagram for explaining the method for storing the new content information in the storage means.

[2.1. How to add content information]
In the information distribution system S in the present embodiment, even if one distribution server 1 out of the plurality of distribution servers 1 withdraws from the distributed content pool 9a due to a failure, maintenance, or the like, all the contents input to the information distribution system S In order to guarantee the information, the same content information is stored in at least two distribution servers 1 respectively.

  In this way, in order to keep the same content information stored in at least two distribution servers 1 in the content storage area of the storage means, the content information held in the distribution server 1 is set as non-permanently held content information. When there is no storage area that is newly added to the content storage area of the storage means, the content information stored in the content storage area of the storage means is not deleted. The non-permanently retained content information is deleted and a storage area for newly adding is secured, and new content information is added to the secured storage area.

  In this embodiment, content information newly added to the distributed content pool 9a by the center server 10 is stored as at least two distribution servers 1 as persistently held content information. In the following, an operation when adding permanently retained content information to the distributed content pool 9a will be described.

  As shown in FIG. 4, when the center server 10 newly adds content information to the distributed content pool 9a, the center server 10 selects the distribution server 1d as an arbitrary distribution server 1, and sends the new content information (hereinafter, referred to as “new content information”) to the distribution server 1d. "Content information B") is requested. This addition request includes the content information B and “deletion prohibited” information.

  Then, the distribution server 1d that has received the request to add the content information B determines two distribution servers 1 that hold the content information B as permanently retained content (here, the distribution servers 1b and 1c), and the content information B is stored. Transmit to distribution servers 1b and 1c.

  The distribution servers 1b and 1c hold the content information B as permanently held content information by storing the information “deletion prohibited” in association with the content information B received from the distribution server 1d. As a method of associating and storing “deletion prohibited” information with the content information B, a method of directly including in the content information B information that can be identified as “deletion prohibited”, or a list of content information to be held Although there is a method of associating “deletion prohibited” information for each information, it may be stored by a method that makes it possible to determine whether or not the content information held by each distribution server 1 is permanently held content information for which deletion is prohibited. Any method may be used.

  Thus, when the content information B is input to the distributed content pool 9a as new content information, the terminal device 2 of the content sharing network 9b can acquire the content information B from the distributed content pool 9a. That is, the terminal device 2 can acquire the content information B by requesting the distribution server 1b or the distribution server 1c to transmit the content information B.

  And since the content information B is held in at least two distribution servers 1 as permanently held content information and will not be deleted, the state in which the same content information is stored in duplicate in at least two distribution servers 1 Even when one distribution server 1 out of the plurality of distribution servers 1 withdraws from the distributed content pool 9a due to failure, maintenance, or the like, all content information input to the information distribution system S can be guaranteed. Become.

  By the way, since the terminal device 2 does not know which distribution server 1 holds the content information B, the terminal device 2 may request the transmission of the content information B to the distribution server 1a that does not hold the content information B. (See FIG. 5 (1).) In this case, the distribution server 1a acquires the content information B from the distribution server 1b or the distribution server 1c that holds the content information B, and transmits the content information B to the requesting terminal device 2. At this time, the distribution server 1a holds the content information B as non-permanent holding content information (see FIGS. 5 (2) and (3)).

  In this way, the distribution server 1 acquires the content information from the other distribution servers 1 when the content information requested to be transmitted from the terminal device 2 is not held. Therefore, content information that is popular content information and that is difficult to be transmitted and received between the terminal devices 2 is held in a number of distribution servers 1.

  In this way, content information newly added from the center server 10 to the distributed content pool 9a is repeatedly stored in the at least two distribution servers 1 as permanent holding content information, while each distribution server 1 has a terminal device. 2 is stored as non-permanent holding content information in response to a transmission request from 2.

  When the distribution server 1a cannot secure a storage area for storing the content information B and cannot store the content information B, the distribution server 1b or the distribution server 1c that holds the content information B Requesting that the content information B be transmitted to the requesting terminal device 2. This also ensures distribution of content information in the distributed content pool 9a.

[2.2. Determination of distribution server 1 to retain permanently retained content information]
Next, a method for determining the distribution server 1 that retains permanently retained content information will be described.

  After a while after the operation, each of the distribution servers 1a to 1d receives the content information from the center server 10 and processes the request for the content information from the terminal device 2 to permanently store the content information in the content storage area of its own storage means. And non-permanently retained content information are stored. That is, as shown in FIG. 6, among all the data storage areas of the content storage area in the storage means, a permanent holding area where permanent holding content information is stored, and a non-permanent holding area where non-permanent holding content information is held And the other storage areas are completely empty areas.

  Each distribution server 1 notifies the other distribution servers 1 of the storage capacity of the non-permanent holding area and the storage capacity of the complete free area as storable free capacity (hereinafter simply referred to as “free capacity”). I am doing so.

  For example, consider a case where the state of the content storage area of the storage means in each of the distribution servers 1a to 1d is as shown in FIG. At this time, the complete free area, non-permanent holding area and permanent holding area are 0 GB (gigabytes), 50 GB and 50 GB in the distribution server 1 a, 0 GB, 3 GB and 57 GB in the distribution server 1 b, and 5 GB, 5 GB and 60 GB in the distribution server 1 c. In the distribution server 1d, they are 5 GB, 5 GB, and 15 GB.

  Accordingly, the “free capacity” of each of the distribution servers 1a to 1d is 50 GB, 3 GB, 10 GB, and 10 GB, and each of the distribution servers 1 a to 1 d holds the information as a free capacity list. For example, in the distribution server 1a, as shown in FIG. 8, a free capacity list including the “free capacity” of the storage means including its own device is held.

  Then, the distribution server 1 that has received the content information addition request from the center server 10 has two distribution servers 1 (including its own device) that can hold the content information related to the addition request based on the free capacity list. To decide. When there are three or more distribution servers 1 that can hold the content information, the two higher distribution servers 1 having a large “free space” are determined as the distribution servers 1 that hold the content information.

  For example, as shown in FIG. 9, when the content information to be added has a data capacity of 4 GB and the “free capacity” of each of the distribution servers 1 a to 1 d is 50 GB, 3 GB, 10 GB, and 10 GB, respectively, the “free capacity” is Among the distribution servers 1 other than the distribution server 1b not exceeding 4 GB, the two higher distribution servers 1a, 1c (or distribution servers 1a, 1d) having a large “free capacity” are determined as distribution servers 1 for holding content information. .

  The distribution servers 1a and 1c (or distribution servers 1a and 1d) store the content information input from the center server 10 into the distributed content pool 9a in the content storage area of the storage unit. For example, when the content information C shown in FIG. 10 (a) is stored in the storage means in which the content storage area is in the state shown in FIG. 10 (b), the state of the content storage area in the storage means is as shown in FIG. 10 (c). become. As described above, when the data capacity of the content information C to be newly added is larger than the complete free capacity of the content storage area in the storage means, the content information C is stored in the content storage area of the storage means before the content information C is acquired. The non-permanently held content information is deleted and the new content information is received after ensuring the complete free space of the content storage area in the storage means.

  By the way, in order to hold the above-described free capacity list in the distribution server 1, it is necessary to notify the “free capacity” of the storage means between the distribution servers 1 before the center server 10 requests to add content information. There is.

  Therefore, at the stage of configuring the distributed content pool 9a, the distribution servers 1 mutually notify the “free capacity” of the storage means, and each distribution server 1 generates a free capacity list. Thereafter, when a new distribution server 1 is added to the distributed content pool 9a, similarly, the newly added distribution server 1 sets the “free capacity” of its storage means to all the distribution servers 1 constituting the distributed content pool 9a. And “free capacity” of each distribution server 1 is acquired.

  Further, when content information is newly input from the center server 10 to the distributed content pool 9a, the “free capacity” of the storage means of the distribution server 1 changes. The change is notified to each other and the free capacity list is updated.

  Here, the information notified between the respective distribution servers 1 is not the data capacity and the complete free capacity of the non-permanent holding content information stored in the content storage area of the storage means of each distribution server 1, By simply setting the “free space” of the storage means, the volume of data to be notified is reduced. Thereby, when notifying the state of the content storage area of the storage unit (hereinafter referred to as “storage unit state”) between the distribution servers 1, the load on the network 8 can be suppressed.

  As described above, in the information distribution system S in the present embodiment, two or more different distribution servers 1 in the distributed content pool 9a hold the same permanently stored content information, and then each distribution server 1 newly adds a content When information is retained, the content information to be deleted is not permanently retained content information, but is non-permanently retained content information. For this reason, the same content information can always exist repeatedly in different distribution servers 1 in the distributed content pool 9a.

  Also, each distribution server 1 grasps the state of the storage means of the other distribution servers 1 from the free capacity list, and determines the holding destination of the content information input from the center server 10 based on this free capacity list. Thus, the center server 10 does not need to grasp the state of the storage means of each distribution server 1.

  Moreover, each distribution server 1 can newly add content information by deleting non-permanently held content information even when there is no complete free space in the content storage area of the storage means. Therefore, it is possible to avoid a situation in which content information cannot be newly added because there is no complete free space in the content storage area of the storage means.

[2.3. Determination of non-persistent retained content information to be deleted]
As described above, each distribution server 1 stores non-permanent holding stored in the content storage area when there is no complete free space in the content storage area of the storage means when trying to store non-permanent holding content information. Delete content information.

  The deletion of the non-permanent retained content information can be performed by randomly selecting the non-permanent retained content information stored in the content storage area of the storage means, but the content that is highly likely to be requested from the content sharing network 9b It is desirable to keep the information without deleting it.

  The content information that is highly likely to be requested from the content sharing network 9b is content information that is hardly shared in the content sharing network 9b, that is, “unpopular content information”. On the other hand, since popular content information is shared in the content sharing network 9b, the content information is requested to the distributed content pool 9a after being shared in the content sharing network 9b. The possibility of coming is low. Accordingly, when the content information with the oldest date and time stored in the content storage area of the storage means is deleted preferentially among the popular content information, the content storage area of the storage means in the distribution server 1 of the distributed content pool 9a becomes larger. It can be used efficiently.

  Therefore, the distribution server 1 in the present embodiment preferentially deletes non-permanently retained content information that is popular in the content sharing network 9b and that has an older storage date and time.

  The content information popular in the content sharing network 9b is determined by the distribution server 1 attempting to delete the non-permanent retained content information inquiring the content sharing network 9b.

  For example, when the content sharing network 9a is a content sharing network using a distributed hash table (hereinafter referred to as “DHT”), the terminal device 2 holding the content information to be deleted is managed. There is a method of making an inquiry to the terminal device 2 (the root terminal device below).

  The content sharing network 9a using the distributed hash table (DHT), for example, as shown in Patent Document 1 described above, each value obtained by hashing unique information such as the IP address of each terminal device 2 with a predetermined hash function It is used as unique identification information (hereinafter referred to as “terminal ID”) of the terminal device 2. The control unit of each terminal device 2 holds terminal IDs and location information (such as IP addresses) of some terminal devices 2 among the plurality of terminal devices 2 forming the content sharing network 9b. The content information between the terminal devices 2 is transmitted and received based on the received information. For example, the name of the content information is hashed with the same hash function as when the terminal ID is generated, and unique identification information (hereinafter referred to as “content ID”) is assigned to each content information. Then, the content information of the associated content ID is managed by the terminal device 2 (hereinafter referred to as “root terminal device”) having a predetermined relationship between each content ID and the terminal ID. Here, the management of the content information is to manage the location information of the terminal device 2 that holds the managed content information. The control unit of each terminal device 2 notifies the location information of the own device to the root terminal device having a predetermined association with the content ID of the content information held by the own device. Further, the control unit of each terminal device 2 holds the content information in the root terminal device having a predetermined association with the desired content information (hereinafter referred to as “content holding terminal device”). Inquire about and obtain the location information. By constructing the network in this way, a P2P type content sharing network is formed. Note that the terminal ID having a predetermined relationship with the content ID can be defined as, for example, a terminal ID that is smaller than the content ID and closest to the content ID.

  As shown in FIG. 11, for example, when there is a request for adding content information C from the center server 10 to the distribution server 1a via the distribution server 1d (see (1) and (2) shown in FIG. 11). The distribution server 1a generates a presence confirmation message regarding content information to be deleted (hereinafter referred to as “content information X”), and transmits this presence confirmation message to any terminal device 2a of the content sharing network 9b. (Refer to (3) shown in FIG. 11). Here, since the possibility that the content information stored in the content storage area of the storage means is less popular as the storage date and time is high, the distribution server 1a stores the content information of the storage means as the content information X. Selection is made from the non-permanent holding content information having the oldest time stored in the area (see FIG. 12). Since the distribution server 1a requests the content information and knows the location information (IP address or the like) of the terminal device 2, for example, the distribution server 1a requests the distribution server 1a for the content information and the terminal device 2a Can be selected.

  At this time, the presence confirmation message is a message including the content ID of the content information X and the location information of the distribution server 1a, and is transferred by the terminal device 2 of the content sharing network 9b and has a predetermined relationship with the content ID. The device 2x is reached (see (4) shown in FIG. 11). Upon receiving the presence confirmation message, the terminal device 2x notifies the distribution server 1a of the presence state of the content information X, that is, the number of the terminal devices 2 that hold the content information X (shown in FIG. 11 ( See 5).

  The distribution server 1a then determines whether the content information X is popular content information based on the presence state of the content information X notified from the terminal device 2x, for example, the number of content holding terminal devices managed by the root terminal device. Is greater than or equal to a predetermined number (for example, two, this number is appropriately adjusted according to the size of the content sharing network 9b and the distributed content pool 9a). For example, when the content information includes two or more content holding terminal devices managed by the root terminal device, the content information is determined to be popular content information.

  The distribution server 1a selects the content information X in order from the oldest non-permanent retained content information stored in the content storage area of the storage means, performs the above-described processing, and the content information X is popular content information. Is deleted from the content storage area of the storage means. When the non-permanently retained content information is deleted in this way and a free area in which the content information C can be stored is created in the content storage area of the storage means, the distribution server 1a receives the content from the distribution server 1d. Information C is acquired.

  In this way, the distribution server 1 determines whether the content information stored in the content storage area of the storage unit is content information that is popular in the content sharing network 9b in order from the content information with the oldest storage date and time, When the content information is popular, the content information is deleted from the content storage area of the storage means. As described above, by preferentially deleting popular content information, the data area of the distributed content pool 9a can be used more efficiently.

  Further, as a method that does not depend on the method of the content sharing network 9b, a method is conceivable in which an arbitrary terminal device 2 configuring the content sharing network 9b checks the presence of content information to be deleted. An arbitrary terminal device 2 selected here may be a method of remembering the terminal device 2 that has sent a request to the distributed content pool 9a.

  For example, when there is non-persistent retained content information in the content storage area of the storage means, the location information (such as the IP address) of the terminal device 2 that has requested this non-persistent retained content information is associated and stored in the content storage area of the storage means. The existence confirmation is performed on the terminal device 2 that has requested the content information in order from the content information with the oldest storage date.

  As shown in FIG. 13, for example, when there is a request for adding content information C from the center server 10 to the distribution server 1a via the distribution server 1d (see (1) and (2) shown in FIG. 13). The distribution server 1a generates a presence confirmation message regarding the content information X (a message including the content ID of the content information X and the location information of the distribution server 1a). And when the terminal device 2 which requested | required the content information X from the delivery server 1a is the terminal device 2a, for example, the delivery server 1a transmits a presence confirmation message to the terminal device 2a (refer (3) shown in FIG. 13). .

  The terminal device 2a that has received the presence confirmation message collects the presence state of the content information X in the content sharing network 9b, that is, the content information X from the other terminal devices 2 (see (4) shown in FIG. 13). The distribution server 1a is notified of the presence state of the content information X (see (5) shown in FIG. 13). And the delivery server 1a determines whether it is popular content information based on the presence state of the content information X notified from the terminal device 2a.

[2.4. Method for Determining Distribution Server 1 for Holding Permanently Stored Content Information]
Next, a method for determining the distribution server 1 that retains permanently retained content information will be described.

  Upon receiving the content information addition request from the center server 10, the distribution server 1 (for example, the distribution server 1d in FIG. 11) preferentially holds the permanently held content information from the distribution server 1 having a high “free capacity” ratio.

  For example, as shown in FIG. 14, in the distribution servers 1a to 1c, when the storage capacity of the content storage area of the storage unit in the initial state is 200 GB, 100 GB, or 100 GB, the distribution server 1 adds 4 GB of permanently retained content information. As a result, distribution servers 1a and 1b having a large free storage capacity are selected (see operation 2 in FIG. 14). Next, distribution servers 1a and 1c having a large free storage capacity are selected as distribution servers 1 to which the permanently retained content information of 4 GB is added (see operation 3 in FIG. 14). As described above, the content information can be efficiently added by retaining the permanently retained content information in order from the distribution server 1 having a large “free space”.

[3. Description of Specific Configuration and Operation of Distribution Server 1]
Next, an example of a specific configuration and operation of the distribution server 1 will be described.

(About the configuration of the distribution server 1)
First, a specific configuration of the distribution server 1 will be described. FIG. 15 is a diagram showing a schematic configuration of the distribution server 1 in the information distribution system S of the present embodiment.

  As the distribution server 1, a general server computer can be applied. As shown in FIG. 15, a control unit 101 for controlling the entire distribution server 1 and a rewritable storage unit 102 having a content storage area for storing content information. And a communication unit 103 for communicating with other distribution servers 1 and terminal devices 2, which are connected to each other via a system bus 110.

  The control unit 101 includes a CPU (Central Processing Unit), an internal memory, and the like. The internal memory stores an information processing program for transmitting / receiving content information and other messages to / from other distribution servers 1 and terminal devices 2, and the CPU stores information processing stored in the internal memory. By reading and executing the program, it functions as an acquisition unit, a storage processing unit, a determination unit, a transmission unit, a transmission request unit, a determination unit, and the like.

  The information processing program may be downloaded to the internal memory of the control unit 101 from another server (for example, the center server 10) connected to the Internet via the communication unit 103, for example. Alternatively, after being recorded on a recording medium such as a CD-ROM, it may be read into the internal memory of the control unit 101 via a recording medium drive (not shown).

(Specific operation of distribution server 1)
The operation of the distribution server 1 configured as described above will be specifically described with reference to the drawings. FIG. 16 is a main process flowchart of the distribution server 1 in this embodiment. The following processes are executed by the control unit 101 of the distribution server 1 functioning as the above-described units.

  When a main power switch (not shown) is turned on or a reset switch (not shown) is operated in the distribution server 1, the distribution server 1 performs an initialization operation (step S1) as shown in FIG. ). Specifically, the CPU of the control unit 101 executes initial setting operations such as permitting access to the storage unit 102 and securing the work area of the internal memory, and sets the information processing program stored in the internal memory as an execution state, and then executes the control unit 101. The function is set as an operating state.

  Next, the control unit 101 performs first free space notification processing for notifying other distribution servers 1 of “free space” in the content storage area of the storage unit 102 (step S2). This first free space notification process is the process of steps S20 and S21 shown in FIG. 17, and will be described in detail later.

  Next, the control unit 101 determines whether or not a content permanent holding request has been received from another distribution server 1 (step S3). In this process, if it is determined that the content permanent holding request has been received (step S3: Yes), the control unit 101 performs a content permanent holding process (step S4). This content permanent holding process is a process of steps S30 to S43 shown in FIG. 18, and will be described in detail later. On the other hand, if it determines with not receiving the content permanent holding request | requirement (step S3: No), the control part 101 will transfer a process to step S5.

  In step S <b> 5, the control unit 101 determines whether or not a content copy request has been received from another distribution server 1. In this process, when it is determined that the content copy request has been received (step S5: Yes), the control unit 101 performs a content copy process (step S6). This content copy process is a process of steps S45 to S47 shown in FIG. 19, and will be described in detail later. On the other hand, when determining that the content copy request has not been received (step S5: No), the control unit 101 shifts the processing to step S7.

  In step S <b> 7, the control unit 101 determines whether a content acquisition request is received from the terminal device 2. In this process, when it is determined that the content acquisition request has been received (step S7: Yes), the control unit 101 performs a content transmission process (step S8). This content transmission process is a process of steps S50 to S58 shown in FIG. 20, and will be described in detail later. On the other hand, if it determines with not receiving the content acquisition request (step S7: No), the control part 101 will transfer a process to step S9.

  In step S <b> 9, the control unit 101 determines whether there is a content information addition request from another distribution server 1. In this process, when the control unit 101 determines that there is a content information addition request (step S9: Yes), it performs a content information addition process (step S10). This content information addition processing is processing in steps S60 to S64 shown in FIG. 21, and will be described in detail later. On the other hand, if it determines with there being no content information addition request | requirement (step S9: No), the control part 101 will transfer a process to step S11.

  In step S <b> 11, the control unit 101 determines whether there is a notification of “free space” from another distribution server 1. In this process, if the control unit 101 determines that there is a notification of “free space” (step S11: Yes), it performs a second free space notification process (step S12). This content transmission process is a process of steps S70 to S72 shown in FIG. 22, and will be described in detail later. On the other hand, if it is determined that there is no notification of “free space” (step S11: No), the control unit 101 performs processing according to the message (step S13).

  When the processes of steps S4, S6, S8, S10, S12, and S13 are completed, the control unit 101 determines whether an end instruction has been detected (step S14). For example, when the power of the self-delivery server 1 is shifted to the OFF state, the control unit 101 detects an end instruction.

  If it is determined in step S14 that an end instruction has been detected (step S14: Yes), the control unit 101 ends the main process, whereas if it is determined that no end instruction has been detected (step S14: No), control is performed. Unit 101 repeats the processing from step S3.

  Next, the first free space notification process in step S2 will be specifically described with reference to the flowchart of FIG. FIG. 17 is a flowchart of the first free capacity notification process in the distribution server 1.

  As shown in FIG. 17, when the first free space notification process is started, the control unit 101 notifies all the distribution servers 1 of its “free space” via the network 8 and the communication unit 103 (step S20). . In other words, the control unit 101 determines the “free capacity” of the content storage area of the storage unit 102 of its own device (added the storage capacity when storing non-permanent content information in addition to the complete free capacity). The information of this “free space” is notified to all the distribution servers 1.

  Next, the control unit 101 selects any one of the other distribution servers 1 and communicates a copy request for a free capacity list (for example, see FIG. 8) to the distribution server 1. This is performed via the unit 103 and the network 8. Thereafter, in response to the request for copying the free space list, the control unit 101 receives the free space list transmitted from the other distribution server 1 via the network 8 and the communication unit 103 (step S21). End the free space notification process. In this way, the control unit 101 functions as a free capacity acquisition unit that acquires the “free capacity” of the storage unit of the plurality of distribution servers 1.

  Next, the content permanent holding process in step S4 will be specifically described with reference to the flowchart in FIG. FIG. 18 is a flowchart of content permanent holding processing in the distribution server 1.

  As illustrated in FIG. 18, when the content permanent holding process is started, the control unit 101 determines whether the new content information (hereinafter referred to as “new content information”) related to the content permanent holding request fits in the “free space”. It is determined whether or not (step S30). Specifically, when the “free capacity” of the content storage area in the storage unit 102 is larger than the data size of the new content information, it is determined that the new content information fits in the “free capacity”.

  In this process, when it is determined that the new content information does not fit in the “free space” (step S30: No), the control unit 101 selects the oldest non-permanent content information as a deletion candidate (step S31). Specifically, the control unit 101 selects non-permanent retained content information with the oldest stored date and time among the non-permanent retained content information stored in the content storage area in the storage unit 102.

  Next, the control unit 101 stores information on the oldest non-permanent retained content information (for example, the name of the non-permanent retained content information) in the storage unit 102 as the non-permanent retained content as the deletion candidate (step S32). The oldest non-permanent retained content information stored here is the same as the content information that was selected as a deletion candidate in step S31.

  Next, the control unit 101 inquires of the content sharing network 9b about the existence state of the non-permanent retained content that is the deletion candidate (step S33). For example, the control unit 101 selects an arbitrary terminal device 2 in the content sharing network 9 b and transmits a presence confirmation message to the selected terminal device 2 via the communication unit 103 and the network 8. The arbitrary terminal device 2 is selected at random from, for example, the terminal devices 2 that have requested content information from the device itself. Further, as described above, the presence confirmation message includes the location information (such as the IP address) of the server 1 and the content ID of the content information of the deletion candidate.

  Next, the control unit 101 receives a response to the inquiry made in step S33 from the terminal device 2 (step S34). That is, the control unit 101 receives information on the presence state transmitted in response to the presence confirmation message via the network 8 and the communication unit 103.

  Next, the control unit 101 determines whether the inquired content information is popular content information based on the response to the inquiry received in Step S34 (Step S35). For example, when the content information for which the presence state is inquired in step S33 is content information held by a predetermined number or more of terminal devices 2 in the content sharing network 9b, it is determined that the content information is popular.

  If it is determined in this process that the content information is not popular (step S35: No), the control unit 101 determines whether the next old non-permanent content information exists (step S36).

  In this process, when it is determined that the next old non-persistent retained content information no longer exists (step S36: No), the control unit 101 determines the oldest non-permanent retained content information as the deletion candidate stored in step S32. It determines as a deletion object (step S39), and transfers a process to step S40.

  On the other hand, if it is determined that the next old non-permanent retained content information exists (step S36: Yes), the next oldest non-permanent retained content information is selected as the deletion candidate non-permanent retained content information (step S37), and step S33. The process of S36 is repeated. That is, the control unit 101 stores the non-permanent retained content information that has not been determined in step S35 among the non-permanent retained content information stored in the content storage area in the storage unit 102 and has an old storage date and time. Selection is made as a deletion candidate, and the processing of steps S33 to S36 is repeated. Therefore, when it is determined that all non-permanent retained content information is not popular content information, that is, when it is determined in step S36 that the next old non-permanent retained content information no longer exists (step S36: No), Of the permanently retained content information, the non-permanently retained content information with the oldest storage date / time is determined as a deletion target (step S39).

  If it is determined in step S35 that the deletion candidate non-permanent content information is popular content information (step S35: Yes), the control unit 101 determines the determined non-permanent content information as a deletion target (step S35). S38), the non-permanent content is deleted so that the new content information fits in the storage unit, and the capacity is secured (step S40). That is, the control unit 101 deletes the non-permanent content information determined to be popular content information in step S35 from the content storage area of the storage unit 102, and a storage area for storing new content information in the storage unit 102 Secure. As described above, the control unit 101 stores content information stored in the content storage area when there is no storage area for storing content information acquired from another device in the content storage area of the storage unit 102 serving as a storage unit. Among these, it functions as a storage processing unit that secures a storage area by deleting non-permanently held content information that is not prohibited from being deleted. This storage processing means selects content information stored in a P2P network formed by a plurality of the terminal devices 2, that is, a predetermined number or more stored in the content sharing network 9b as content information to be deleted.

  When the process of step S40 is completed, or when it is determined in step S30 that the new content information can be accommodated in the “free space” (step S30: Yes), the control unit 101 distributes the content reception preparation completion message to the request source. A reply is made to the server 1 (step S41). That is, the control unit 101 sends a content reception preparation completion message for notifying the distribution server 1 that has transmitted the content permanent holding request that the content information is ready via the communication unit 103 and the network 8. Send. This content reception preparation completion message includes information on the “free space” of the content storage area when new content information is stored in the content storage area of the storage unit 102. The server 1 updates the free capacity list based on this “free capacity” information.

  Next, the control unit 101 receives the update message of the free capacity list transmitted from the distribution server 1 that has received the content reception preparation completion message via the network 8 and the communication unit 103 (step S42). The free space list update message includes information on the free space list, and the control unit 101 updates the free space list stored in the storage unit 102 and adds other content information in a new state. The “free capacity” of the distribution server 1 is updated. In this way, the control unit 101 functions as a free capacity acquisition unit that acquires the “free capacity” of the storage unit of the plurality of distribution servers 1.

  Next, the control unit 101 receives new content information from another distribution server 1 that has made a content permanent retention request via the network 8 and the communication unit 103, and stores it as permanent retention content information in the content storage area of the storage unit 102. Hold (step S43). Since the content prohibition information is transmitted in association with the content information transmitted from the other distribution server 1 that has made the content holding request, the control unit 101 has received the information based on the deletion prohibition information. The content information is stored in the storage unit 102 together with deletion prohibition information (for example, a deletion prohibition flag) as permanently retained content information. Thus, the control unit 101 is an acquisition unit that acquires content information from other devices together with information indicating whether or not deletion is prohibited, and a storage unit that stores information acquired from other devices together with information about whether or not deletion is prohibited. It functions as a storage processing means for storing in the unit 102.

  Next, the content copy process start in step S6 will be specifically described with reference to the flowchart of FIG. FIG. 19 is a flowchart of content copy processing in the distribution server 1.

  As shown in FIG. 19, when the content copy process is started, the control unit 101 determines the data size of the content information related to the content copy request based on the information stored in the storage unit 102. Then, the data size of the content information is notified to the other distribution server 1 of the request source via the communication unit 103 and the network 8 (step S45).

  Next, the control unit 101 determines whether copy preparation completion has been received from the other distribution server 1 of the request source via the network 8 and the communication unit 103 (step S46). In this process, if it is determined that the copy preparation completion has been received (step S46: Yes), the control unit 101 retrieves the requested content information from the content storage area of the storage unit 102, and associates the “deletion prohibited” information with it. Instead, the extracted content information is transmitted to the other distribution server 1 of the request source via the communication unit 103 and the network 8 (step S47), and the content copy process is terminated.

  Next, the content transmission processing in step S8 will be specifically described with reference to the flowchart in FIG. FIG. 20 is a flowchart of content transmission processing in the distribution server 1.

  As shown in FIG. 20, when the content transmission process is started, the control unit 101 determines whether or not the content information requested from the terminal device 2 is held (step S50). As described above, when the control unit 101 receives a content information transmission request from the terminal device 2, the control unit 101 determines whether content information corresponding to the transmission request is stored in the storage unit 102 that is a storage unit. Function.

  If it is determined in this process that the requested content information is not held (step S50: No), the control unit 101 searches for another distribution server 1 that holds the content information. Then, a content copy request, which is a content information copy request, is made to the other distribution server 1 holding the content information via the communication unit 103 and the network 8 (step S51).

  In response to the content copy request, the control unit 101 receives information on the data size of the content information transmitted from the other distribution server 1 that holds the content information (step S52), and receives the content information of this data size. It is determined whether or not a complete free capacity to hold exists in the content storage area of the storage unit 102 (step S53).

  In this process, if it is determined that the complete free space that can hold the requested content information is not held (step S53: No), the control unit 101 deletes the non-permanently held content information and It is determined whether or not a content storage area can be secured (step S54).

  In this process, if it is determined that the content storage area can be secured (step S54: Yes), the control unit 101 determines non-permanent retained content information necessary for securing a complete free capacity, and this non-permanent retained The content information is deleted from the content storage area of the storage unit 102 (step S55). Thereby, a storage area for newly holding content information is secured in the content storage area of the storage unit 102. The process of step S55 is executed by performing the same process as the process of steps S31 to S36 described above, for example.

  When the process of step S55 ends, or when it is determined that the complete free space that can hold the content information requested in step S53 is held (step S53: Yes), the control unit 101 performs step In S 51, a copy preparation completion message is notified to the other distribution server 1 that has made the content copy request via the communication unit 103 and the network 8. And the control part 101 receives the content information transmitted from the said other delivery server 1 after that via the network 8 and the communication part 103, and memorize | stores it in the content storage area of the memory | storage part 102 (step S56). The content information received at this time is not associated with “deletion prohibited” information, and the control unit 101 stores the received content information in the content storage area of the storage unit 102 as non-permanent holding content information. As described above, the control unit 101 acquires content information determined that content information corresponding to the transmission request is not stored in the storage unit 102 serving as a storage unit, together with information indicating whether or not deletion is prohibited from other distribution servers 1. It functions as an acquisition means.

  When the process of step S56 is completed or when it is determined that the content information requested in step S50 is held (step S50: Yes), the control unit 101 sends a request to the terminal device 2 that has requested the content information. Then, the requested content information is transmitted via the communication unit 103 and the network 8 (step S57). In this way, the control unit makes a transmission request for content information determined to be stored in the storage unit 102 that is a storage unit, or content information acquired from the distribution server 1 when not stored in the storage unit 102. It functions as a transmitting means for transmitting to the terminal device 2.

  On the other hand, when it is determined in step S54 that the storage area cannot be secured in the content storage area of the storage unit 102 by deleting the non-permanently retained content information (step S54: No), the control unit 101 responds to the request from the terminal device 2. The other distribution server 1 that holds the content information is requested to transmit the content information according to the request to the terminal device 2 that has requested transmission of the content information via the communication unit 103 and the network 8 ( Step S58). As described above, when the storage unit 102 cannot secure a storage area for storing the content information corresponding to the transmission request from the terminal device 2, the control unit 101 stores the content information corresponding to the transmission request. It functions as a transmission request means for requesting the other distribution server 1 to transmit the content information corresponding to the transmission request to the terminal device 2 that has made the transmission request.

  When the process of step S57 or step S58 ends, the control unit 101 ends the content transmission process.

  Next, the content information addition processing in step S10 will be specifically described with reference to the flowchart in FIG. FIG. 21 is a flowchart of content information addition processing in the distribution server 1.

  As shown in FIG. 21, when the content information addition process is started, the control unit 101 determines two distribution servers 1 having a large “free capacity” based on the free capacity list stored in the storage unit 102 (step S60). . As described above, when the control unit 101 receives a request for adding content information from another apparatus, the control unit 101 stores the content information corresponding to the addition request according to the “free space” of the storage unit of the plurality of distribution servers 1. It functions as a determination means for determining the server 1. This determination means selects a predetermined number of distribution servers 1 for storing content information in response to the addition request, in order from a plurality of distribution servers 1, starting from the distribution server 1 having the largest “free space” in the storage means. Do.

  The control unit 101 transmits a content holding request message to the distribution server 1 determined as described above via the communication unit 103 and the network 8 (step S61). When the selected distribution server 1 is the own device, no content holding request is made to the own device. In this way, the control unit 101 functions as an additional processing unit that stores the content information corresponding to the addition request to the determined distribution server 1.

  Next, the control unit 101 determines whether or not a content reception preparation completion message has been received from all the distribution servers 1 that have transmitted the content holding request message in step S61 (step S62). In this process, the control unit 101 waits until a content reception preparation completion message is received from all the distribution servers 1 (step S62: No). When all the receptions are completed (step S62: Yes), the process proceeds to step S63. Transition. When the content reception preparation completion message cannot be received from all the distribution servers 1 even after the predetermined period has elapsed, the control unit 101 determines that the distribution server 1 that cannot receive the content reception preparation completion message has left the distributed content pool 9a or cannot communicate. If it is determined that there is, another distribution server 1 is selected and a content holding request message is transmitted.

  In step S <b> 63, the control unit 101 transmits a free capacity update message to all the distribution servers 1 via the communication unit 103 and the network 8. That is, the content reception preparation completion message includes information on “free capacity” of the distribution server 1, and the control unit 101 updates the free capacity list stored in the storage unit 102 based on this free capacity. The free space update message including the information of the free space list updated in this way is transmitted to all distribution servers 1 via the communication unit 103 and the network 8.

  Thereafter, the control unit 101 transmits content information to be newly added to the two distribution servers 1 selected in step S60 via the communication unit 103 and the network 8 (step S64). The content information transmitted at this time is associated with “deletion prohibited” information. If the distribution server 1 selected in step S60 is its own device, the newly added content information is stored in the content storage area of the storage unit 102 as permanently retained content information.

  Next, the second free space notification process in step S12 will be specifically described with reference to the flowchart of FIG. FIG. 22 is a flowchart of the second free space notification process in the distribution server 1.

  As shown in FIG. 22, when the second free space notification process is started, the control unit 101 newly adds to the free space list stored in the storage unit 102 and intends to participate in the distributed content pool 9a (hereinafter, “ "Free capacity" information is added (referred to as "new distribution server 1") (step S70). This “free space” information is information included in the free space notification determined to have been received in step S11.

  Next, the control unit 101 determines whether or not a copy request for the free space list has been received from the newly participating distribution server 1 via the network 8 and the communication unit 103 (step S71). In this process, if it is determined that the copy request has been received from the new participation distribution server (step S71: Yes), the control unit 101 sends the free space list to the new participation distribution server 1 via the communication unit 103 and the network 8. Transmit (step S72).

  When the process of step S72 is completed, or when it is determined in step S71 that it is not received from the new participation distribution server 1 (step S71: No), the control unit 101 ends the second free capacity notification process. As described above, the control unit 101 updates the free capacity list based on the “free capacity” information transmitted from the new distribution server 1, and transmits the updated free capacity list to the new distribution server 1. As a result, the new distribution server 1 can hold the free capacity list.

  As described above, the distribution server 1 according to the present embodiment acquires content information from other devices together with information indicating whether or not deletion is prohibited, and stores this content information together with information about whether or not deletion is prohibited in the storage unit. When the storage unit does not have a storage area for storing content information acquired from another device, the distribution server 1 selects content information that is not prohibited from being deleted from the content information stored in the storage unit. The storage area is secured by deletion, and the content information acquired from another device is stored in the secured storage area together with information indicating whether or not deletion is prohibited. In this way, in the distributed content pool 9a, content information can always exist in the distribution server 1, and storage can be used efficiently by determining and deleting content information that may be deleted. Furthermore, by making the content information to be deleted popular content information with a low possibility of being requested from the content sharing network 9b and having an old stored date and time, the storage in the distributed content pool 9a can be used more efficiently.

[4. Other Embodiments]
In the above-described embodiment, content information popular in the content sharing network 9b is deleted from the storage unit among content information that is not prohibited from being deleted. However, a predetermined number or more of distribution servers 1 in the distributed content pool 9a. It is also possible to delete content information that is held in and not prohibited from being deleted from the storage means. At this time, the control unit 101 functions as a storage processing unit that selects, as content information to be deleted, content information stored in a plurality of distribution servers 1 in the distributed content pool 9a by a predetermined number or more.

  In the above embodiment, when there is a content information transmission request from the terminal device 2, the content information related to the request is not in the storage unit 102 of the own device, and the content is sent from another distribution server 1. When the storage area of the storage unit 102 for acquiring information cannot be secured, to the terminal device 2 that has made a transmission request for content information to another distribution server 1 storing content information corresponding to the transmission request A request for directly transmitting the content information is made to transmit the content information to the terminal device 2 (see (3) and (4) shown in FIG. 23), and to the other distribution server 1 not storing the content. You may make it request | require to transmit (refer (5) shown in FIG. 23). In this way, when there is a request for transmitting content information from the terminal device 2, the control unit 101 does not have content information related to the request in the storage unit 102 of its own device, and the content is transmitted from another distribution server 1. When the storage area of the storage unit 102 for acquiring information cannot be secured, it may function as a transmission request unit that requests transmission to another distribution server 1 that does not store content.

  Further, in the above embodiment, the distribution server 1 that has received a request for adding new content information from the center server 10 determines the distribution server 1 to which new content information is added in consideration of the storage contents of each distribution server 1. However, the distribution server 1 in which the center server 10 grasps the storage content of the storage unit 102 of each distribution server 1 and inputs (transmits) new content information from the storage content of the storage unit 102 of each distribution server 1. And the content information may be directly input to the determined distribution server 1. At this time, the control unit of the center server 10 functions as a determination unit that determines the distribution server 1 that holds the new content information, and a transmission unit that transmits the content information to the determined distribution server 1.

  In the above embodiment, the non-permanent content information that is highly likely to be requested from the content sharing network 9b is deleted, but the non-permanent content content stored in the storage means is deleted. Information may be selected at random.

  Further, the distributed content pool 9a may be configured by a network using a P2P type distributed hash table in the same manner as the content sharing network 9b. In this case, each distribution server 1 is assigned unique server identification information, and each piece of content information held by the distribution server 1 is assigned a content ID that is unique content identification information. And the server identification which transmits the server identification information of the own apparatus to the distribution server 1 which has the server identification information corresponding to the content identification information allocated to the content information memorize | stored in the memory | storage part 102 for the control part 101 of each delivery server 1 Information transmitting means, server identification information storage means for storing server identification information of the distribution server 1 that holds content information to which content identification information corresponding to the server identification information of its own device is assigned, Content information stored in a server identification information storage unit of the apparatus or a server identification information storage unit of another distribution server 1 is determined as content information to be deleted and can be functioned as a storage processing unit that deletes the content information. .

It is a figure which shows an example of the connection aspect of each terminal device of each information delivery system in one Embodiment of this invention, each delivery server, and a center server. It is a figure which shows a mode that a terminal device acquires content information from the delivery server of a distributed content pool. It is a figure which shows a mode that a terminal device acquires content information from the delivery server of a distributed content pool. It is a figure which shows a mode that content information is added to the delivery server of a distributed content pool. It is a figure which shows a mode that a terminal device acquires content information from the delivery server of a distributed content pool. It is a figure which shows the state of the content storage area of the memory | storage means of a delivery server. It is a figure which shows the state of the content storage area of the memory | storage means of each delivery server. It is a figure which shows the state of the free capacity list which a delivery server hold | maintains. It is explanatory drawing of the determination method of the delivery server which hold | maintains new content information. It is explanatory drawing of the storage method to the memory | storage means of new content information. It is explanatory drawing of the determination method of the delivery server which hold | maintains new content information. It is explanatory drawing of the determination method of the delivery server which hold | maintains new content information. It is explanatory drawing of the determination method of the delivery server which hold | maintains new content information. It is explanatory drawing of the determination method of the delivery server which hold | maintains new content information. It is a figure which shows schematic structure of a delivery server. It is a main process flowchart of a delivery server. It is a 1st free capacity notification process flowchart of a delivery server. It is a flowchart of the content permanent holding process of a delivery server. It is a flowchart of the content copy process in a delivery server. It is a flowchart of the content transmission process in a delivery server. It is a flowchart of the content information addition process in a delivery server. It is a flowchart of the 2nd free capacity notification process in a delivery server. It is a figure which shows a mode that a terminal device acquires content information from the delivery server of a distributed content pool.

Explanation of symbols

S Information distribution system 1 Distribution server 2 Terminal device 10 Center server 8 Network 9a Distributed content pool 9b Content sharing network 101 Distribution server control unit 102 Distribution server storage unit 103 Distribution server communication unit

Claims (11)

In the distribution server in an information distribution system that includes a plurality of distribution servers that hold a plurality of content information and transmit content information in response to a request from a terminal device,
Storage means for storing the content information;
Acquisition means for acquiring content information from other devices together with information on whether or not deletion is prohibited;
Storage processing means for storing in the storage means together with information on whether or not to delete the content information acquired from the other device,
The storage processing means has content that is not prohibited from being deleted from the content information stored in the storage means when the storage means does not have a storage area for storing content information acquired from the other device. A distribution server, wherein a storage area is secured by deleting information, and content information acquired from the other device is stored in the secured storage area. A determination unit that determines whether content information corresponding to the transmission request is stored in the storage unit when a transmission request for the content information is received from the terminal device;
Transmission means for transmitting the content information determined by the determination means to be stored in the storage means to the terminal device that made the transmission request,
The acquisition unit acquires the content information determined not to be stored in the storage unit by the determination unit together with information on whether or not deletion is prohibited from another distribution server,
The distribution server according to claim 1, wherein the transmission unit transmits the content information acquired from the other distribution server to the terminal device that has made the transmission request.   When a storage area for storing content information corresponding to the transmission request from the terminal device cannot be secured by the storage processing means, to another distribution server storing the content information corresponding to the transmission request The distribution server according to claim 2, further comprising transmission request means for requesting the content information corresponding to the transmission request to be transmitted to the terminal device that has made the transmission request.   The transmission request unit stores content information corresponding to the transmission request when the storage processing unit cannot secure a storage area for storing content information acquired from the other distribution server in the storage unit. 4. The distribution server according to claim 3, wherein the distribution server is requested to transmit the content to another distribution server that does not store the content. Free capacity acquisition means for acquiring the free capacity of the storage means of the plurality of distribution servers, respectively;
A distribution server that stores content information corresponding to the addition request according to the free capacity of the storage means of the plurality of distribution servers acquired by the free capacity acquisition means when a content information addition request is received from another device A determination means for determining
The distribution server according to any one of claims 1 to 4, further comprising an additional processing unit that stores content information corresponding to the addition request in the distribution server determined by the determination unit.   The determination means selects a predetermined number of distribution servers for storing content information in response to the addition request, in order from a distribution server having a large free space in the storage means among the plurality of distribution servers. Item 6. The distribution server according to Item 5.   The storage processing means selects content information stored in a P2P network formed by a plurality of terminal devices as the content information to be deleted, a predetermined number or more. 2. The distribution server according to item 1.   The distribution according to claim 1, wherein the storage processing unit selects content information stored in the plurality of distribution servers at a predetermined number or more as the content information to be deleted. server.   A program that causes a computer to function as each means of the distribution server according to any one of claims 1 to 8. In an information distribution system comprising a plurality of distribution servers that hold a plurality of content information and transmit content information in response to a request from a terminal device,
Each of the distribution servers
Storage means for storing the content information;
Acquisition means for acquiring content information from other devices together with information on whether or not deletion is prohibited;
Storage processing means for storing in the storage means together with information on whether or not to delete the content information acquired from the other device,
The storage processing means has content that is not prohibited from being deleted from the content information stored in the storage means when the storage means does not have a storage area for storing content information acquired from the other device. An information distribution system, wherein a storage area is secured by deleting information, and content information acquired from the other device is stored in the secured storage area. In the storage method of the content information in the distribution server that stores a plurality of pieces of content information in the storage unit and extracts and transmits the content information according to the request from the terminal device,
A step of acquiring content information from other devices together with information indicating whether or not deletion is prohibited by an acquisition unit;
When the storage means does not have a storage area for storing content information acquired from another device, content information that is not prohibited from being deleted is stored among the content information stored in the storage means. And deleting the contents to secure a storage area, and storing the content information acquired from another device together with the information indicating whether the deletion is prohibited or not in the secured storage area. Memory method.