Tuesday, September 18, 2012

Zookeeper watchers and events, a (very) short summary

Here is a summary of what events are expected if you set ChildrenWatcher, DataWatcher or ExistsWatcher on a znode :

WARNING : none means that no event is triggered, do no confuse with EventType.None

Do not forget this basic rule : Watches are one time trigger, once a watch has been triggered you must register it once again if you want to be notified. Moreover due to network latency you can miss one or several changes that happen just before the watch is re-registered.

An expired zookeeper session also means that all your watches are gone, you have to create them once again.

More informations here.

Hope it helps...