The @PLUGIN@ plugin allows to share stream events between two Gerrit instances sharing the same git repositories and database.
The plugin needs to be installed in both instances and every time a stream event occurs in one of the instances (see [more events info] (https://gerrit-review.googlesource.com/Documentation/cmd-stream-events.html#events)), the event is forwarded to the other instance which re-plays it. This way, the output of the stream-events command is the same, no matter what instance a client is connected to.
For this to work, http must be enabled in both instances and the plugin must be configured with valid credentials. For further information, refer to config documentation.