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https://issues.apache.org/jira/browse/ZOOKEEPER-832?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14563719#comment-14563719
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Germán Blanco commented on ZOOKEEPER-832:
-----------------------------------------
We crossed messages there, sorry.
My intuition was actually wrong. There doesn't seem to be anything wrong with
the C code. It seems this is a synchronization issue. The thread that listens
for connections starts before the ZkDatabase is loaded, so it reads a low zxid
and kills the session. This was not noticeable before, because the client
looped until the zxid in the server was high enough and then connected. I think
that the cleanest thing is to put a Latch and wait for the ZkDatabase to load
before accepting connections.
I will update the patch with this fix (the Latch to wait for the ZkDatabase to
load) on top of the previous patch and that should pass the tests.
> 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: Bug
> Components: server
> Affects Versions: 3.4.5, 3.5.0
> Environment: All
> Reporter: Ryan Holmes
> Assignee: Germán Blanco
> Priority: Blocker
> Fix For: 3.4.7, 3.5.2, 3.6.0
>
> Attachments: ZOOKEEPER-832.patch, ZOOKEEPER-832.patch,
> ZOOKEEPER-832.patch, ZOOKEEPER-832.patch, ZOOKEEPER-832.patch
>
>
> 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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