Hi Chang, it sounds like you may have an issue with your cluster environment/setup, or perhaps a resource (GC/mem) issue. Have you looked through the troubleshooting guide? https://cwiki.apache.org/confluence/display/ZOOKEEPER/Troubleshooting
In particular 1000 clients connecting should be fine, I've personally seen clusters of 7-10 thousand clients. Keep in mind that each session establishment is essentially a write (so the quorum in involved) and what we typically see there is that the cluster configuration has issues. 14 seconds for a ping response is huge and indicates one of the following may be an underlying cause: 1) are you running in a virtualized environment? 2) are you co-locating other services on the same host(s) that make up the ZK serving cluster? 3) have you followed the admin guide's "things to avoid"? http://zookeeper.apache.org/doc/r3.3.3/zookeeperAdmin.html#sc_commonProblems In particular ensuring that you are not swapping or going into gc pause (both on the server and the client) a) try turning on GC logging and ensure that you are not going into GC pause, see the troubleshooting guide, this is the most common cause of high latency for the clients b) ensure that you are not swapping c) ensure that other processes are not causing log writing (transactional logging) to be slow. Patrick On Wed, Apr 13, 2011 at 6:35 AM, Chang Song <[email protected]> wrote: > Hello, folks. > > We have ran into a very serious issue with Zookeeper. > Here's a brief scenario. > > We have some Zookeeper clients with session timeout of 15 sec (thus 5 sec > ping), let's called > these clients, group A. > > Now 1000 new clients (let's call these, group B) starts up at the same time > trying to > connect to a three-node ZK ensemble, creating ZK createSession stampede. > > Now almost all clients in group A is not able to exchange ping within session > expire time (15 sec). > Thus clients in group A drops out of the cluster. > > We have looked into this issue a bit, found mostly synchronous nature of > session queue processing. > Latency between ping request and response ranges from 10ms up to 14 seconds > during this login stampede. > > Since session timeout is serious matter for our cluster, thus ping should be > done in psuedo realtime fashion. > > I don't know exactly how these ping timeout policy in clients and server, but > failure to receive ping > response in clients due to zookeeper login session seem very nonsense to me. > > Shouldn't we have a separate ping/heartbeat queue and thread? > Or even multiple ping queues/threads to keep realtime heartbeat? > > THis is very serious issue with Zookeeper for our mission-critical system. > Could anyone > look into this? > > I will try to file a bug. > > Thank you. > > Chang > > >
