[3.2.3 backport] changes feed error will not cause blip clients to disconnect

In the scenario that CBL starts a continuous pull replication and then the changes feed has an error like ErrChannelFeed, the changes feed will exit and the underlying blip connection will remain open. The result of this behavior is that CBL replication will remain “busy” and connected, but no changes will ever be received by the CBL client.

Sync Gateway has no way to send a unsolicited message to CBL with an error condition, and does not check a message for Error-Code so in order to terminate the replicator.

The case where ErrChannelFeed was observed was the following case of a timeout on the N1QL query:

In order to fix this, Sync Gateway should close the blip connection in a manner that CBL will restart the replicator. The plan is to use a cancelation context similar to . A cancellable context with a parent of DatabaseContext.CancelContext will be placed on BlipSyncContext and can be cancelled when this scenario is hit. This will shut down the blip connection and CBL replicator will retry the connection automatically.