--- title: Virtual Service description: Configuration affecting label/content routing, sni routing, etc. location: https://istio.io/docs/reference/config/networking/v1alpha3/virtual-service.html layout: protoc-gen-docs generator: protoc-gen-docs number_of_entries: 22 ---

Configuration affecting traffic routing. Here are a few terms useful to define in the context of traffic routing.

`Service` a unit of application behavior bound to a unique name in a service registry. Services consist of multiple network endpoints implemented by workload instances running on pods, containers, VMs etc.

`Service versions (a.k.a. subsets)` - In a continuous deployment scenario, for a given service, there can be distinct subsets of instances running different variants of the application binary. These variants are not necessarily different API versions. They could be iterative changes to the same service, deployed in different environments (prod, staging, dev, etc.). Common scenarios where this occurs include A/B testing, canary rollouts, etc. The choice of a particular version can be decided based on various criterion (headers, url, etc.) and/or by weights assigned to each version. Each service has a default version consisting of all its instances.

`Source` - A downstream client calling a service.

`Host` - The address used by a client when attempting to connect to a service.

`Access model` - Applications address only the destination service (Host) without knowledge of individual service versions (subsets). The actual choice of the version is determined by the proxy/sidecar, enabling the application code to decouple itself from the evolution of dependent services.

A `VirtualService` defines a set of traffic routing rules to apply when a host is addressed. Each routing rule defines matching criteria for traffic of a specific protocol. If the traffic is matched, then it is sent to a named destination service (or subset/version of it) defined in the registry.

The source of traffic can also be matched in a routing rule. This allows routing to be customized for specific client contexts.

The following example on Kubernetes, routes all HTTP traffic by default to pods of the reviews service with label “version: v1”. In addition, HTTP requests with path starting with /wpcatalog/ or /consumercatalog/ will be rewritten to /newcatalog and sent to pods with label “version: v2”.

    apiVersion: networking.istio.io/v1alpha3
    kind: VirtualService
    metadata:
      name: reviews-route
    spec:
      hosts:
      - reviews.prod.svc.cluster.local
      http:
      - match:
        - uri:
            prefix: "/wpcatalog"
        - uri:
            prefix: "/consumercatalog"
        rewrite:
          uri: "/newcatalog"
        route:
        - destination:
            host: reviews.prod.svc.cluster.local
            subset: v2
      - route:
        - destination:
            host: reviews.prod.svc.cluster.local
            subset: v1

A subset/version of a route destination is identified with a reference to a named service subset which must be declared in a corresponding `DestinationRule`.

    apiVersion: networking.istio.io/v1alpha3
    kind: DestinationRule
    metadata:
      name: reviews-destination
    spec:
      host: reviews.prod.svc.cluster.local
      subsets:
      - name: v1
        labels:
          version: v1
      - name: v2
        labels:
          version: v2

## CorsPolicy

Describes the Cross-Origin Resource Sharing (CORS) policy, for a given service. Refer to CORS for further details about cross origin resource sharing. For example, the following rule restricts cross origin requests to those originating from example.com domain using HTTP POST/GET, and sets the `Access-Control-Allow-Credentials` header to false. In addition, it only exposes `X-Foo-bar` header and sets an expiry period of 1 day.

    apiVersion: networking.istio.io/v1alpha3
    kind: VirtualService
    metadata:
      name: ratings-route
    spec:
      hosts:
      - ratings.prod.svc.cluster.local
      http:
      - route:
        - destination:
            host: ratings.prod.svc.cluster.local
            subset: v1
        corsPolicy:
          allowOrigin:
          - example.com
          allowMethods:
          - POST
          - GET
          allowCredentials: false
          allowHeaders:
          - X-Foo-Bar
          maxAge: "24h"

Field | Type | Description
--- | --- | ---
`allowOrigin` | `string[]` | The list of origins that are allowed to perform CORS requests. The content will be serialized into the Access-Control-Allow-Origin header. Wildcard * will allow all origins.
`allowMethods` | `string[]` | List of HTTP methods allowed to access the resource. The content will be serialized into the Access-Control-Allow-Methods header.
`allowHeaders` | `string[]` | List of HTTP headers that can be used when requesting the resource. Serialized to Access-Control-Allow-Headers header.
`exposeHeaders` | `string[]` | A white list of HTTP headers that the browsers are allowed to access. Serialized into Access-Control-Expose-Headers header.
`maxAge` | `google.protobuf.Duration` | Specifies how long the results of a preflight request can be cached. Translates to the `Access-Control-Max-Age` header.
`allowCredentials` | `google.protobuf.BoolValue` | Indicates whether the caller is allowed to send the actual request (not the preflight) using credentials. Translates to `Access-Control-Allow-Credentials` header.

## Destination

Destination indicates the network addressable service to which the request/connection will be sent after processing a routing rule. The destination.host should unambiguously refer to a service in the service registry. Istio’s service registry is composed of all the services found in the platform’s service registry (e.g., Kubernetes services, Consul services), as well as services declared through the ServiceEntry resource.

Note for Kubernetes users: When short names are used (e.g. “reviews” instead of “reviews.default.svc.cluster.local”), Istio will interpret the short name based on the namespace of the rule, not the service. A rule in the “default” namespace containing a host “reviews will be interpreted as “reviews.default.svc.cluster.local”, irrespective of the actual namespace associated with the reviews service. To avoid potential misconfigurations, it is recommended to always use fully qualified domain names over short names.

The following Kubernetes example routes all traffic by default to pods of the reviews service with label “version: v1” (i.e., subset v1), and some to subset v2, in a Kubernetes environment.

    apiVersion: networking.istio.io/v1alpha3
    kind: VirtualService
    metadata:
      name: reviews-route
      namespace: foo
    spec:
      hosts:
      - reviews # interpreted as reviews.foo.svc.cluster.local
      http:
      - match:
        - uri:
            prefix: "/wpcatalog"
        - uri:
            prefix: "/consumercatalog"
        rewrite:
          uri: "/newcatalog"
        route:
        - destination:
            host: reviews # interpreted as reviews.foo.svc.cluster.local
            subset: v2
      - route:
        - destination:
            host: reviews # interpreted as reviews.foo.svc.cluster.local
            subset: v1

And the associated DestinationRule

    apiVersion: networking.istio.io/v1alpha3
    kind: DestinationRule
    metadata:
      name: reviews-destination
      namespace: foo
    spec:
      host: reviews # interpreted as reviews.foo.svc.cluster.local
      subsets:
      - name: v1
        labels:
          version: v1
      - name: v2
        labels:
          version: v2

The following VirtualService sets a timeout of 5s for all calls to productpage.prod.svc.cluster.local service in Kubernetes. Notice that there are no subsets defined in this rule. Istio will fetch all instances of productpage.prod.svc.cluster.local service from the service registry and populate the sidecar’s load balancing pool. Also, notice that this rule is set in the istio-system namespace but uses the fully qualified domain name of the productpage service, productpage.prod.svc.cluster.local. Therefore the rule’s namespace does not have an impact in resolving the name of the productpage service.

    apiVersion: networking.istio.io/v1alpha3
    kind: VirtualService
    metadata:
      name: my-productpage-rule
      namespace: istio-system
    spec:
      hosts:
      - productpage.prod.svc.cluster.local # ignores rule namespace
      http:
      - timeout: 5s
        route:
        - destination:
            host: productpage.prod.svc.cluster.local

To control routing for traffic bound to services outside the mesh, external services must first be added to Istio’s internal service registry using the ServiceEntry resource. VirtualServices can then be defined to control traffic bound to these external services. For example, the following rules define a Service for wikipedia.org and set a timeout of 5s for http requests.

    apiVersion: networking.istio.io/v1alpha3
    kind: ServiceEntry
    metadata:
      name: external-svc-wikipedia
    spec:
      hosts:
      - wikipedia.org
      location: MESH_EXTERNAL
      ports:
      - number: 80
        name: example-http
        protocol: HTTP
      resolution: DNS

    apiVersion: networking.istio.io/v1alpha3
    kind: VirtualService
    metadata:
      name: my-wiki-rule
    spec:
      hosts:
      - wikipedia.org
      http:
      - timeout: 5s
        route:
        - destination:
            host: wikipedia.org

Field | Type | Description
--- | --- | ---
`host` | `string` | REQUIRED. The name of a service from the service registry. Service names are looked up from the platform’s service registry (e.g., Kubernetes services, Consul services, etc.) and from the hosts declared by ServiceEntry. Traffic forwarded to destinations that are not found in either of the two, will be dropped. Note for Kubernetes users: When short names are used (e.g. “reviews” instead of “reviews.default.svc.cluster.local”), Istio will interpret the short name based on the namespace of the rule, not the service. A rule in the “default” namespace containing a host “reviews will be interpreted as “reviews.default.svc.cluster.local”, irrespective of the actual namespace associated with the reviews service. To avoid potential misconfigurations, it is recommended to always use fully qualified domain names over short names.
`subset` | `string` | The name of a subset within the service. Applicable only to services within the mesh. The subset must be defined in a corresponding DestinationRule.
`port` | `PortSelector` | Specifies the port on the host that is being addressed. If a service exposes only a single port it is not required to explicitly select the port.

## HTTPFaultInjection

HTTPFaultInjection can be used to specify one or more faults to inject while forwarding http requests to the destination specified in a route. Fault specification is part of a VirtualService rule. Faults include aborting the Http request from downstream service, and/or delaying proxying of requests. A fault rule MUST HAVE delay or abort or both.

Note: Delay and abort faults are independent of one another, even if both are specified simultaneously.

Field | Type | Description
--- | --- | ---
`delay` | `HTTPFaultInjection.Delay` | Delay requests before forwarding, emulating various failures such as network issues, overloaded upstream service, etc.
`abort` | `HTTPFaultInjection.Abort` | Abort Http request attempts and return error codes back to downstream service, giving the impression that the upstream service is faulty.

## HTTPFaultInjection.Abort

Abort specification is used to prematurely abort a request with a pre-specified error code. The following example will return an HTTP 400 error code for 1 out of every 1000 requests to the “ratings” service “v1”.

    apiVersion: networking.istio.io/v1alpha3
    kind: VirtualService
    metadata:
      name: ratings-route
    spec:
      hosts:
      - ratings.prod.svc.cluster.local
      http:
      - route:
        - destination:
            host: ratings.prod.svc.cluster.local
            subset: v1
        fault:
          abort:
            percentage:
              value: 0.1
            httpStatus: 400

The httpStatus field is used to indicate the HTTP status code to return to the caller. The optional percentage field can be used to only abort a certain percentage of requests. If not specified, all requests are aborted.

Field | Type | Description
--- | --- | ---
`percent` | `int32` | Percentage of requests to be aborted with the error code provided (0-100). Use of integer `percent` value is deprecated. Use the double `percentage` field instead.
`httpStatus` | `int32 (oneof)` | REQUIRED. HTTP status code to use to abort the Http request.
`percentage` | `Percent` | Percentage of requests to be aborted with the error code provided.

## HTTPFaultInjection.Delay

Delay specification is used to inject latency into the request forwarding path. The following example will introduce a 5 second delay in 1 out of every 1000 requests to the “v1” version of the “reviews” service from all pods with label env: prod

    apiVersion: networking.istio.io/v1alpha3
    kind: VirtualService
    metadata:
      name: reviews-route
    spec:
      hosts:
      - reviews.prod.svc.cluster.local
      http:
      - match:
        - sourceLabels:
            env: prod
        route:
        - destination:
            host: reviews.prod.svc.cluster.local
            subset: v1
        fault:
          delay:
            percentage:
              value: 0.1
            fixedDelay: 5s

The fixedDelay field is used to indicate the amount of delay in seconds. The optional percentage field can be used to only delay a certain percentage of requests. If left unspecified, all request will be delayed.

Field | Type | Description
--- | --- | ---
`percent` | `int32` | Percentage of requests on which the delay will be injected (0-100). Use of integer `percent` value is deprecated. Use the double `percentage` field instead.
`fixedDelay` | `google.protobuf.Duration (oneof)` | REQUIRED. Add a fixed delay before forwarding the request. Format: 1h/1m/1s/1ms. MUST be >=1ms.
`percentage` | `Percent` | Percentage of requests on which the delay will be injected.

## HTTPMatchRequest

HttpMatchRequest specifies a set of criterion to be met in order for the rule to be applied to the HTTP request. For example, the following restricts the rule to match only requests where the URL path starts with /ratings/v2/ and the request contains a custom `end-user` header with value `jason`.

    apiVersion: networking.istio.io/v1alpha3
    kind: VirtualService
    metadata:
      name: ratings-route
    spec:
      hosts:
      - ratings.prod.svc.cluster.local
      http:
      - match:
        - headers:
            end-user:
              exact: jason
          uri:
            prefix: "/ratings/v2/"
          ignoreUriCase: true
        route:
        - destination:
            host: ratings.prod.svc.cluster.local

HTTPMatchRequest CANNOT be empty.

Field | Type | Description
--- | --- | ---
`uri` | `StringMatch` | URI to match values are case-sensitive and formatted as follows: `exact: "value"` for exact string match `prefix: "value"` for prefix-based match `regex: "value"` for ECMAscript style regex-based match Note: Case-insensitive matching could be enabled via the `ignore_uri_case` flag.
`scheme` | `StringMatch` | URI Scheme values are case-sensitive and formatted as follows: `exact: "value"` for exact string match `prefix: "value"` for prefix-based match `regex: "value"` for ECMAscript style regex-based match
`method` | `StringMatch` | HTTP Method values are case-sensitive and formatted as follows: `exact: "value"` for exact string match `prefix: "value"` for prefix-based match `regex: "value"` for ECMAscript style regex-based match
`authority` | `StringMatch` | HTTP Authority values are case-sensitive and formatted as follows: `exact: "value"` for exact string match `prefix: "value"` for prefix-based match `regex: "value"` for ECMAscript style regex-based match
`headers` | `map<string, StringMatch>` | The header keys must be lowercase and use hyphen as the separator, e.g. x-request-id. Header values are case-sensitive and formatted as follows: `exact: "value"` for exact string match `prefix: "value"` for prefix-based match `regex: "value"` for ECMAscript style regex-based match Note: The keys `uri`, `scheme`, `method`, and `authority` will be ignored.
`port` | `uint32` | Specifies the ports on the host that is being addressed. Many services only expose a single port or label ports with the protocols they support, in these cases it is not required to explicitly select the port.
`sourceLabels` | `map<string, string>` | One or more labels that constrain the applicability of a rule to workloads with the given labels. If the VirtualService has a list of gateways specified at the top, it should include the reserved gateway `mesh` in order for this field to be applicable.
`gateways` | `string[]` | Names of gateways where the rule should be applied to. Gateway names at the top of the VirtualService (if any) are overridden. The gateway match is independent of sourceLabels.
`queryParams` | `map<string, StringMatch>` | Query parameters for matching. Ex: - For a query parameter like “?key=true”, the map key would be “key” and the string match could be defined as `exact: "true"`. - For a query parameter like “?key”, the map key would be “key” and the string match could be defined as `exact: ""`. - For a query parameter like “?key=123”, the map key would be “key” and the string match could be defined as `regex: "\d+$"`. Note that this configuration will only match values like “123” but not “a123” or “123a”. Note: `prefix` matching is currently not supported.
`ignoreUriCase` | `bool` | Flag to specify whether the URI matching should be case-insensitive. Note: The case will be ignored only in the case of `exact` and `prefix` URI matches.

## HTTPRedirect

HTTPRedirect can be used to send a 301 redirect response to the caller, where the Authority/Host and the URI in the response can be swapped with the specified values. For example, the following rule redirects requests for /v1/getProductRatings API on the ratings service to /v1/bookRatings provided by the bookratings service.

    apiVersion: networking.istio.io/v1alpha3
    kind: VirtualService
    metadata:
      name: ratings-route
    spec:
      hosts:
      - ratings.prod.svc.cluster.local
      http:
      - match:
        - uri:
            exact: /v1/getProductRatings
        redirect:
          uri: /v1/bookRatings
          authority: newratings.default.svc.cluster.local
      ...

Field | Type | Description
--- | --- | ---
`uri` | `string` | On a redirect, overwrite the Path portion of the URL with this value. Note that the entire path will be replaced, irrespective of the request URI being matched as an exact path or prefix.
`authority` | `string` | On a redirect, overwrite the Authority/Host portion of the URL with this value.

## HTTPRetry

Describes the retry policy to use when a HTTP request fails. For example, the following rule sets the maximum number of retries to 3 when calling ratings:v1 service, with a 2s timeout per retry attempt.

    apiVersion: networking.istio.io/v1alpha3
    kind: VirtualService
    metadata:
      name: ratings-route
    spec:
      hosts:
      - ratings.prod.svc.cluster.local
      http:
      - route:
        - destination:
            host: ratings.prod.svc.cluster.local
            subset: v1
        retries:
          attempts: 3
          perTryTimeout: 2s
          retryOn: gateway-error,connect-failure,refused-stream

Field | Type | Description
--- | --- | ---
`attempts` | `int32` | REQUIRED. Number of retries for a given request. The interval between retries will be determined automatically (25ms+). Actual number of retries attempted depends on the httpReqTimeout.
`perTryTimeout` | `google.protobuf.Duration` | Timeout per retry attempt for a given request. format: 1h/1m/1s/1ms. MUST BE >=1ms.
`retryOn` | `string` | Specifies the conditions under which retry takes place. One or more policies can be specified using a ‘,’ delimited list. See the supported policies and here for more details.

## HTTPRewrite

HTTPRewrite can be used to rewrite specific parts of a HTTP request before forwarding the request to the destination. Rewrite primitive can be used only with HTTPRouteDestination. The following example demonstrates how to rewrite the URL prefix for api call (/ratings) to ratings service before making the actual API call.

    apiVersion: networking.istio.io/v1alpha3
    kind: VirtualService
    metadata:
      name: ratings-route
    spec:
      hosts:
      - ratings.prod.svc.cluster.local
      http:
      - match:
        - uri:
            prefix: /ratings
        rewrite:
          uri: /v1/bookRatings
        route:
        - destination:
            host: ratings.prod.svc.cluster.local
            subset: v1

Field | Type | Description
--- | --- | ---
`uri` | `string` | rewrite the path (or the prefix) portion of the URI with this value. If the original URI was matched based on prefix, the value provided in this field will replace the corresponding matched prefix.
`authority` | `string` | rewrite the Authority/Host header with this value.

## HTTPRoute

Describes match conditions and actions for routing HTTP/1.1, HTTP2, and gRPC traffic. See VirtualService for usage examples.

Field | Type | Description
--- | --- | ---
`match` | `HTTPMatchRequest[]` | Match conditions to be satisfied for the rule to be activated. All conditions inside a single match block have AND semantics, while the list of match blocks have OR semantics. The rule is matched if any one of the match blocks succeed.
`route` | `HTTPRouteDestination[]` | A http rule can either redirect or forward (default) traffic. The forwarding target can be one of several versions of a service (see glossary in beginning of document). Weights associated with the service version determine the proportion of traffic it receives.
`redirect` | `HTTPRedirect` | A http rule can either redirect or forward (default) traffic. If traffic passthrough option is specified in the rule, route/redirect will be ignored. The redirect primitive can be used to send a HTTP 301 redirect to a different URI or Authority.
`rewrite` | `HTTPRewrite` | Rewrite HTTP URIs and Authority headers. Rewrite cannot be used with Redirect primitive. Rewrite will be performed before forwarding.
`timeout` | `google.protobuf.Duration` | Timeout for HTTP requests.
`retries` | `HTTPRetry` | Retry policy for HTTP requests.
`fault` | `HTTPFaultInjection` | Fault injection policy to apply on HTTP traffic at the client side. Note that timeouts or retries will not be enabled when faults are enabled on the client side.
`mirror` | `Destination` | Mirror HTTP traffic to a another destination in addition to forwarding the requests to the intended destination. Mirrored traffic is on a best effort basis where the sidecar/gateway will not wait for the mirrored cluster to respond before returning the response from the original destination. Statistics will be generated for the mirrored destination.
`corsPolicy` | `CorsPolicy` | Cross-Origin Resource Sharing policy (CORS). Refer to CORS for further details about cross origin resource sharing.
`appendHeaders` | `map<string, string>` | Use of `append_headers` is deprecated. Use the `headers` field instead.
`removeResponseHeaders` | `string[]` | Use of `remove_response_header` is deprecated. Use the `headers` field instead.
`appendResponseHeaders` | `map<string, string>` | Use of `append_response_headers` is deprecated. Use the `headers` field instead.
`removeRequestHeaders` | `string[]` | Use of `remove_request_headers` is deprecated. Use the `headers` field instead.
`appendRequestHeaders` | `map<string, string>` | Use of `append_request_headers` is deprecated. Use the `headers` field instead.
`headers` | `Headers` | Header manipulation rules

## HTTPRouteDestination

Each routing rule is associated with one or more service versions (see glossary in beginning of document). Weights associated with the version determine the proportion of traffic it receives. For example, the following rule will route 25% of traffic for the “reviews” service to instances with the “v2” tag and the remaining traffic (i.e., 75%) to “v1”.

    apiVersion: networking.istio.io/v1alpha3
    kind: VirtualService
    metadata:
      name: reviews-route
    spec:
      hosts:
      - reviews.prod.svc.cluster.local
      http:
      - route:
        - destination:
            host: reviews.prod.svc.cluster.local
            subset: v2
          weight: 25
        - destination:
            host: reviews.prod.svc.cluster.local
            subset: v1
          weight: 75

And the associated DestinationRule

    apiVersion: networking.istio.io/v1alpha3
    kind: DestinationRule
    metadata:
      name: reviews-destination
    spec:
      host: reviews.prod.svc.cluster.local
      subsets:
      - name: v1
        labels:
          version: v1
      - name: v2
        labels:
          version: v2

Traffic can also be split across two entirely different services without having to define new subsets. For example, the following rule forwards 25% of traffic to reviews.com to dev.reviews.com

    apiVersion: networking.istio.io/v1alpha3
    kind: VirtualService
    metadata:
      name: reviews-route-two-domains
    spec:
      hosts:
      - reviews.com
      http:
      - route:
        - destination:
            host: dev.reviews.com
          weight: 25
        - destination:
            host: reviews.com
          weight: 75

Field | Type | Description
--- | --- | ---
`destination` | `Destination` | REQUIRED. Destination uniquely identifies the instances of a service to which the request/connection should be forwarded to.
`weight` | `int32` | REQUIRED. The proportion of traffic to be forwarded to the service version. (0-100). Sum of weights across destinations SHOULD BE == 100. If there is only one destination in a rule, the weight value is assumed to be 100.
`removeResponseHeaders` | `string[]` | Use of `remove_response_header` is deprecated. Use the `headers` field instead.
`appendResponseHeaders` | `map<string, string>` | Use of `append_response_headers` is deprecated. Use the `headers` field instead.
`removeRequestHeaders` | `string[]` | Use of `remove_request_headers` is deprecated. Use the `headers` field instead.
`appendRequestHeaders` | `map<string, string>` | Use of `append_request_headers` is deprecated. Use the `headers` field instead.
`headers` | `Headers` | Header manipulation rules

## Headers

Header manipulation rules

Field | Type | Description
--- | --- | ---
`request` | `Headers.HeaderOperations` | Header manipulation rules to apply before forwarding a request to the destination service
`response` | `Headers.HeaderOperations` | Header manipulation rules to apply before returning a response to the caller

## Headers.HeaderOperations

HeaderOperations Describes the header manipulations to apply

Field | Type | Description
--- | --- | ---
`set` | `map<string, string>` | Overwrite the headers specified by key with the given values
`add` | `map<string, string>` | Append the given values to the headers specified by keys (will create a comma-separated list of values)
`remove` | `string[]` | Remove a the specified headers

## L4MatchAttributes

L4 connection match attributes. Note that L4 connection matching support is incomplete.

Field | Type | Description
--- | --- | ---
`destinationSubnets` | `string[]` | IPv4 or IPv6 ip addresses of destination with optional subnet. E.g., a.b.c.d/xx form or just a.b.c.d.
`port` | `uint32` | Specifies the port on the host that is being addressed. Many services only expose a single port or label ports with the protocols they support, in these cases it is not required to explicitly select the port.
`sourceLabels` | `map<string, string>` | One or more labels that constrain the applicability of a rule to workloads with the given labels. If the VirtualService has a list of gateways specified at the top, it should include the reserved gateway `mesh` in order for this field to be applicable.
`gateways` | `string[]` | Names of gateways where the rule should be applied to. Gateway names at the top of the VirtualService (if any) are overridden. The gateway match is independent of sourceLabels.

## Percent

Percent specifies a percentage in the range of [0.0, 100.0].

Field | Type | Description
--- | --- | ---
`value` | `double` |

## PortSelector

PortSelector specifies the number of a port to be used for matching or selection for final routing.

Field | Type | Description
--- | --- | ---
`number` | `uint32 (oneof)` | Valid port number

## RouteDestination

L4 routing rule weighted destination.

Field | Type | Description
--- | --- | ---
`destination` | `Destination` | REQUIRED. Destination uniquely identifies the instances of a service to which the request/connection should be forwarded to.
`weight` | `int32` | REQUIRED. The proportion of traffic to be forwarded to the service version. If there is only one destination in a rule, all traffic will be routed to it irrespective of the weight.

## StringMatch

Describes how to match a given string in HTTP headers. Match is case-sensitive.

Field | Type | Description
--- | --- | ---
`exact` | `string (oneof)` | exact string match
`prefix` | `string (oneof)` | prefix-based match
`regex` | `string (oneof)` | ECMAscript style regex-based match

## TCPRoute

Describes match conditions and actions for routing TCP traffic. The following routing rule forwards traffic arriving at port 27017 for mongo.prod.svc.cluster.local to another Mongo server on port 5555.

    apiVersion: networking.istio.io/v1alpha3
    kind: VirtualService
    metadata:
      name: bookinfo-Mongo
    spec:
      hosts:
      - mongo.prod.svc.cluster.local
      tcp:
      - match:
        - port: 27017
        route:
        - destination:
            host: mongo.backup.svc.cluster.local
            port:
              number: 5555

Field | Type | Description
--- | --- | ---
`match` | `L4MatchAttributes[]` | Match conditions to be satisfied for the rule to be activated. All conditions inside a single match block have AND semantics, while the list of match blocks have OR semantics. The rule is matched if any one of the match blocks succeed.
`route` | `RouteDestination[]` | The destination to which the connection should be forwarded to.

## TLSMatchAttributes

TLS connection match attributes.

Field | Type | Description
--- | --- | ---
`sniHosts` | `string[]` | REQUIRED. SNI (server name indicator) to match on. Wildcard prefixes can be used in the SNI value, e.g., *.com will match foo.example.com as well as example.com. An SNI value must be a subset (i.e., fall within the domain) of the corresponding virtual serivce’s hosts.
`destinationSubnets` | `string[]` | IPv4 or IPv6 ip addresses of destination with optional subnet. E.g., a.b.c.d/xx form or just a.b.c.d.
`port` | `uint32` | Specifies the port on the host that is being addressed. Many services only expose a single port or label ports with the protocols they support, in these cases it is not required to explicitly select the port.
`sourceLabels` | `map<string, string>` | One or more labels that constrain the applicability of a rule to workloads with the given labels. If the VirtualService has a list of gateways specified at the top, it should include the reserved gateway `mesh` in order for this field to be applicable.
`gateways` | `string[]` | Names of gateways where the rule should be applied to. Gateway names at the top of the VirtualService (if any) are overridden. The gateway match is independent of sourceLabels.

## TLSRoute

Describes match conditions and actions for routing unterminated TLS traffic (TLS/HTTPS) The following routing rule forwards unterminated TLS traffic arriving at port 443 of gateway called “mygateway” to internal services in the mesh based on the SNI value.

    apiVersion: networking.istio.io/v1alpha3
    kind: VirtualService
    metadata:
      name: bookinfo-sni
    spec:
      hosts:
      - "*.bookinfo.com"
      gateways:
      - mygateway
      tls:
      - match:
        - port: 443
          sniHosts:
          - login.bookinfo.com
        route:
        - destination:
            host: login.prod.svc.cluster.local
      - match:
        - port: 443
          sniHosts:
          - reviews.bookinfo.com
        route:
        - destination:
            host: reviews.prod.svc.cluster.local

Field | Type | Description
--- | --- | ---
`match` | `TLSMatchAttributes[]` | REQUIRED. Match conditions to be satisfied for the rule to be activated. All conditions inside a single match block have AND semantics, while the list of match blocks have OR semantics. The rule is matched if any one of the match blocks succeed.
`route` | `RouteDestination[]` | The destination to which the connection should be forwarded to.

## VirtualService

Field | Type | Description
--- | --- | ---
`hosts` | `string[]` | REQUIRED. The destination hosts to which traffic is being sent. Could be a DNS name with wildcard prefix or an IP address. Depending on the platform, short-names can also be used instead of a FQDN (i.e. has no dots in the name). In such a scenario, the FQDN of the host would be derived based on the underlying platform. A single VirtualService can be used to describe all the traffic properties of the corresponding hosts, including those for multiple HTTP and TCP ports. Alternatively, the traffic properties of a host can be defined using more than one VirtualService, with certain caveats. Refer to the Operations Guide for details. Note for Kubernetes users: When short names are used (e.g. “reviews” instead of “reviews.default.svc.cluster.local”), Istio will interpret the short name based on the namespace of the rule, not the service. A rule in the “default” namespace containing a host “reviews will be interpreted as “reviews.default.svc.cluster.local”, irrespective of the actual namespace associated with the reviews service. To avoid potential misconfigurations, it is recommended to always use fully qualified domain names over short names. The hosts field applies to both HTTP and TCP services. Service inside the mesh, i.e., those found in the service registry, must always be referred to using their alphanumeric names. IP addresses are allowed only for services defined via the Gateway.
`gateways` | `string[]` | The names of gateways and sidecars that should apply these routes. A single VirtualService is used for sidecars inside the mesh as well as for one or more gateways. The selection condition imposed by this field can be overridden using the source field in the match conditions of protocol-specific routes. The reserved word `mesh` is used to imply all the sidecars in the mesh. When this field is omitted, the default gateway (`mesh`) will be used, which would apply the rule to all sidecars in the mesh. If a list of gateway names is provided, the rules will apply only to the gateways. To apply the rules to both gateways and sidecars, specify `mesh` as one of the gateway names.
`http` | `HTTPRoute[]` | An ordered list of route rules for HTTP traffic. HTTP routes will be applied to platform service ports named ‘http-’/‘http2-’/‘grpc-*’, gateway ports with protocol HTTP/HTTP2/GRPC/ TLS-terminated-HTTPS and service entry ports using HTTP/HTTP2/GRPC protocols. The first rule matching an incoming request is used.
`tls` | `TLSRoute[]` | An ordered list of route rule for non-terminated TLS & HTTPS traffic. Routing is typically performed using the SNI value presented by the ClientHello message. TLS routes will be applied to platform service ports named ‘https-’, ‘tls-’, unterminated gateway ports using HTTPS/TLS protocols (i.e. with “passthrough” TLS mode) and service entry ports using HTTPS/TLS protocols. The first rule matching an incoming request is used. NOTE: Traffic ‘https-’ or ‘tls-’ ports without associated virtual service will be treated as opaque TCP traffic.
`tcp` | `TCPRoute[]` | An ordered list of route rules for opaque TCP traffic. TCP routes will be applied to any port that is not a HTTP or TLS port. The first rule matching an incoming request is used.
`exportTo` | `string[]` | A list of namespaces to which this virtual service is exported. Exporting a virtual service allows it to be used by sidecars and gateways defined in other namespaces. This feature provides a mechanism for service owners and mesh administrators to control the visibility of virtual services across namespace boundaries. If no namespaces are specified then the virtual service is exported to all namespaces by default. The value “.” is reserved and defines an export to the same namespace that the virtual service is declared in. Similarly the value “*” is reserved and defines an export to all namespaces. NOTE: in the current release, the `exportTo` value is restricted to “.” or “*” (i.e., the current namespace or all namespaces).