Hi, I have a question about zookeeper sessions (within a cluster). I've noticed in our production servers that some of our clients lose connection to zookeeper then our client application comes down (and we automatically bring it back and it reconnects to zk just fine). It seems to be a session expiration failure (from the investigation done so far).
2017-09-14 09:26:11,516 org.apache.zookeeper.ClientCnxn INFO [main-SendThread(***:2181)] Opening socket connection to server *** /***:2181. Will not attempt to authenticate using SASL (unknown error) 2017-09-14 09:26:11,517 org.apache.zookeeper.ClientCnxn INFO [main-SendThread(***:2181)] Socket connection established to *** /***:2181, initiating session 2017-09-14 09:26:11,519 org.apache.zookeeper.ClientCnxn DEBUG [main-SendThread(***:2181)] Session establishment request sent on *** /***:2181 2017-09-14 09:26:11,520 org.apache.zookeeper.ClientCnxn INFO [main-SendThread(***:2181)] Unable to reconnect to ZooKeeper service, session 0x3256a2e5b6090079 has expired, closing socket connection My question is related to how session expiration works, I noticed on many of the client machines the times across these machines were all off (by anywhere from 1 minute to 20 minutes - which was resolved after discovery - haven't verified this completely yet). Can this directly affect session expiration within the zookeeper cluster? * I read the following in https://wiki.apache.org/hadoop/ZooKeeper/FAQ , "Expirations happens when the cluster does not hear from the client within the specified session timeout period (i.e. no heartbeat).". So in some case it seems like if the times were wrong across the machines its possible one of the clients could of effectively sent a heart beat in the past (not sure about this tbh) and then the cluster expires the session? * I don't have the zookeeper node log for the above time to see what was going on in zookeeper when the cluster determined the session expired. * Is there any additional logging I can turn on to troubleshoot zk session expiration issues? Thanks! This message is intended exclusively for the individual or entity to which it is addressed. This communication may contain information that is proprietary, privileged, confidential or otherwise legally exempt from disclosure. If you are not the named addressee, or have been inadvertently and erroneously referenced in the address line, you are not authorized to read, print, retain, copy or disseminate this message or any part of it. If you have received this message in error, please notify the sender immediately by e-mail and delete all copies of the message. (ID m031214)
