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Posted to dev@zookeeper.apache.org by "Germán Blanco (JIRA)" <ji...@apache.org> on 2013/06/19 08:51:22 UTC
[jira] [Commented] (ZOOKEEPER-832) Invalid session id causes
infinite loop during automatic reconnect
[ https://issues.apache.org/jira/browse/ZOOKEEPER-832?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13687676#comment-13687676 ]
Germán Blanco commented on ZOOKEEPER-832:
-----------------------------------------
This issue becomes more frequent if a ramdisk is used to store ZooKeeper server data and there are not many servers in the cluster (3 or 5). There is a possibility that all the nodes go through a complete restart without allowing for the election to complete and that means data will be lost (in our case that is not important since data that is more than a few seconds old is not relevant any more). When that happens, all ZooKeeper clients of the cluster need to be restarted as well.
> Invalid session id causes infinite loop during automatic reconnect
> ------------------------------------------------------------------
>
> Key: ZOOKEEPER-832
> URL: https://issues.apache.org/jira/browse/ZOOKEEPER-832
> Project: ZooKeeper
> Issue Type: Improvement
> Components: c client, java client
> Affects Versions: 3.3.1
> Environment: Mac OS X 10.6.4
> JVM 1.6.0_20
> Reporter: Ryan Holmes
> Fix For: 3.5.0
>
>
> Steps to reproduce:
> 1.) Connect to a standalone server using the Java client.
> 2.) Stop the server.
> 3.) Delete the contents of the data directory (i.e. the persisted session data).
> 4.) Start the server.
> The client now automatically tries to reconnect but the server refuses the connection because the session id is invalid. The client and server are now in an infinite loop of attempted and rejected connections. While this situation represents a catastrophic failure and the current behavior is not incorrect, it appears that there is no way to detect this situation on the client and therefore no way to recover.
> The suggested improvement is to send an event to the default watcher indicating that the current state is "session invalid", similar to how the "session expired" state is handled.
> Server log output (repeats indefinitely):
> 2010-08-05 11:48:08,283 - INFO [NIOServerCxn.Factory:0.0.0.0/0.0.0.0:2181:NIOServerCnxn$Factory@250] - Accepted socket connection from /127.0.0.1:63292
> 2010-08-05 11:48:08,284 - INFO [NIOServerCxn.Factory:0.0.0.0/0.0.0.0:2181:NIOServerCnxn@751] - Refusing session request for client /127.0.0.1:63292 as it has seen zxid 0x44 our last zxid is 0x0 client must try another server
> 2010-08-05 11:48:08,284 - INFO [NIOServerCxn.Factory:0.0.0.0/0.0.0.0:2181:NIOServerCnxn@1434] - Closed socket connection for client /127.0.0.1:63292 (no session established for client)
> Client log output (repeats indefinitely):
> 11:47:17 org.apache.zookeeper.ClientCnxn startConnect INFO line 1000 - Opening socket connection to server localhost/127.0.0.1:2181
> 11:47:17 org.apache.zookeeper.ClientCnxn run WARN line 1120 - Session 0x12a3ae4e893000a for server null, unexpected error, closing socket connection and attempting reconnect
> java.net.ConnectException: Connection refused
> at sun.nio.ch.SocketChannelImpl.checkConnect(Native Method)
> at sun.nio.ch.SocketChannelImpl.finishConnect(SocketChannelImpl.java:574)
> at org.apache.zookeeper.ClientCnxn$SendThread.run(ClientCnxn.java:1078)
> 11:47:17 org.apache.zookeeper.ClientCnxn cleanup DEBUG line 1167 - Ignoring exception during shutdown input
> java.nio.channels.ClosedChannelException
> at sun.nio.ch.SocketChannelImpl.shutdownInput(SocketChannelImpl.java:638)
> at sun.nio.ch.SocketAdaptor.shutdownInput(SocketAdaptor.java:360)
> at org.apache.zookeeper.ClientCnxn$SendThread.cleanup(ClientCnxn.java:1164)
> at org.apache.zookeeper.ClientCnxn$SendThread.run(ClientCnxn.java:1129)
> 11:47:17 org.apache.zookeeper.ClientCnxn cleanup DEBUG line 1174 - Ignoring exception during shutdown output
> java.nio.channels.ClosedChannelException
> at sun.nio.ch.SocketChannelImpl.shutdownOutput(SocketChannelImpl.java:649)
> at sun.nio.ch.SocketAdaptor.shutdownOutput(SocketAdaptor.java:368)
> at org.apache.zookeeper.ClientCnxn$SendThread.cleanup(ClientCnxn.java:1171)
> at org.apache.zookeeper.ClientCnxn$SendThread.run(ClientCnxn.java:1129)
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