We have just released a Developer Preview build of Jira 3.11 as part of our Early Access Program. This new build is for the benefit of plugin developers so that they can make their plugins ready for Jira 3.11.

This developer preview is vitally important. In Jira 3.11, we upgraded Lucene from 1.9 to 2.2. This is a fairly big jump, and a great many methods have been deprecated or removed by Lucene. So that means that if your Jira plugin uses or depends on Lucene, it almost certainly will not work with Jira 3.11.
So, if you have developed custom plugins that use Lucene, either publicly in the Jira Plugin Library, or privately for you company’s internal use, it is critical that you test those plugins against the Jira 3.11 EAP.
You should make any necessary changes to the plugin, and be prepared to release those fixes in conjunction with Jira 3.11, so that users will have a smooth upgrade experience.
If you have any trouble with the EAP or the upgrade process, please contact me at developer-support@atlassian.com for assistance.

Jira 3.11 EAP