## 1.5.0 2018-10-02

Linkerd 1.5.0 adds the long awaited ability to make Linkerd config changes with
zero downtime! 🤯 This release adds the `socketOptions.reusePort` config property which allows
multiple processes to bind to the same port.  In this way, you can start a new Linkerd process
and wait for it to start serving requests before gracefully shutting down the old Linkerd process.
Note that this feature is only available on Linux 3.9 distributions and newer.

This release features contributions from [Applause](https://github.com/ApplauseAQI), ThreeComma,
GuteFrage GmbH, and [Buoyant](https://github.com/buoyantio).  An extra special thank you to
[Zack Angelo](https://github.com/zackangelo) for laying the groundwork in Finagle for the reusePort
feature!

Full release notes:

* **Breaking Change**: The `threshold` and `windowSize` options have been removed from the `failureThreshold` config in the Namerd interpreter.  These options were of limited value and are no longer supported by Finagle.
* Socket Options:
  * Certain socket options may now be set on Linkerd servers by adding a `socketOptions` config in a server config.
  * Add support for the `SO_REUSEPORT` socket option.  This allows multiple processes to bind to the same port and is a great way to do zero downtime Linkerd deploys.
* Istio features are now marked as deprecated.
* Marathon:
  * Ensure traffic is not sent to Marathon services during their health-check grace period.
* Use AsyncAppender for console logging so that logging does not impact Linkerd performance.
* Upgrade to Finagle 18.9.1

Signed-off-by: Alex Leong <alex@buoyant.io>