Major Description
We run a Zookeeper 3.5.1-alpha quorum on EC2 instances and the quorum members could be changed, for example, one peer could be replaced by a new EC2 instance due to EC2 instance termination. We use Apache Curator 3.1.0 as the zookeeper client. During our testing, we found the SharedValue data structure could hold stall data during and after one peer is replaced and thus led to the system failure.
We look into the SharedValue code. Seems it always returns the value from an in-memory reference variable and the value is only updated by a watcher. If for any reason, the watch is lost, then the value would never get a chance to be updated again.
Right now, we added a connection state listener to force SharedValue to call readValue(), i.e., read the data from zookeeper directly, if the connection state has been changed to RECONNECTED to work around this issue.
It would be great if this issue could be fixed in Curator directly.
