How to programmatically detect which server in a ZooKeeper ensemble a client is connected to?
I'm using the Apache Curator API and I am listening for state changes in connection by registering ConnectionStateListener. I would like to know which server in the ensemble a client is connected to when the client reconnects if the server it was connected to goes down.
You can see this in the logs produced by Curator. In the example output below, the CuratorFramework
client has been given 4 different ZooKeeper instances in the connectionString
that it can connect to. As can be seen in the log, it choses the first:
21:13:45.384 [main] INFO org.apache.curator.framework.imps.CuratorFrameworkImpl - Starting
21:13:45.386 [main] INFO org.apache.zookeeper.ZooKeeper - Initiating client connection, connectString=127.0.0.1:2181,127.0.0.1:2182,127.0.0.1:2183,127.0.0.1:2184 sessionTimeout=60000 watcher=org.apache.curator.ConnectionState@2876f0c
21:13:45.388 [main-SendThread(127.0.0.1:2181)] INFO org.apache.zookeeper.ClientCnxn - Opening socket connection to server 127.0.0.1/127.0.0.1:2181. Will not attempt to authenticate using SASL (unknown error)
21:13:45.388 [main-SendThread(127.0.0.1:2181)] INFO org.apache.zookeeper.ClientCnxn - Socket connection established to 127.0.0.1/127.0.0.1:2181, initiating session
21:13:45.392 [main-SendThread(127.0.0.1:2181)] INFO org.apache.zookeeper.ClientCnxn - Session establishment complete on server 127.0.0.1/127.0.0.1:2181, sessionid = 0x14aac461eb70004, negotiated timeout = 40000
In case the ZooKeeper server that the client has connected to crashes, you will also see the new server that the client connects to in the logs:
21:23:03.675 [main-SendThread(127.0.0.1:2182)] INFO org.apache.zookeeper.ClientCnxn - Opening socket connection to server 127.0.0.1/127.0.0.1:2182. Will not attempt to authenticate using SASL (unknown error)
21:23:03.677 [main-SendThread(127.0.0.1:2182)] INFO org.apache.zookeeper.ClientCnxn - Socket connection established to 127.0.0.1/127.0.0.1:2182, initiating session
21:23:03.697 [main-SendThread(127.0.0.1:2182)] INFO org.apache.zookeeper.ClientCnxn - Session establishment complete on server 127.0.0.1/127.0.0.1:2182, sessionid = 0x14aac461eb70004, negotiated timeout = 40000
21:23:03.697 [main-EventThread] INFO org.apache.curator.framework.state.ConnectionStateManager - State change: RECONNECTED
来源:https://stackoverflow.com/questions/27515774/how-to-programmatically-detect-which-server-in-ensemble-client-is-connected-to