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https://issues.apache.org/jira/browse/ZOOKEEPER-832?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13088549#comment-13088549
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Laxman commented on ZOOKEEPER-832:
----------------------------------
This problem is due to server closing the connection silently when Client's
lastSeenZxid is greater than Server's current zxid.
This is due to following snippet code in NIOServerCnxn.
{code}
if (connReq.getLastZxidSeen() >
zk.getZKDatabase().getDataTreeLastProcessedZxid()) {
String msg = "Refusing session request for client "
+ sock.socket().getRemoteSocketAddress()
+ " as it has seen zxid 0x"
+ Long.toHexString(connReq.getLastZxidSeen())
+ " our last zxid is 0x"
+
Long.toHexString(zk.getZKDatabase().getDataTreeLastProcessedZxid())
+ " client must try another server";
LOG.info(msg);
throw new CloseRequestException(msg);
}
{code}
In which case this may happen apart from data dir deletion scenario mentioned
in current issue?
What is the impact of removal of this check so that it will throw
SessionExpired and Client can establish a new session rather falling into
infinite loop?
> 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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