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https://issues.apache.org/jira/browse/ZOOKEEPER-1599?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13538308#comment-13538308
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Flavio Junqueira commented on ZOOKEEPER-1599:
---------------------------------------------
I wanted to understand if there is anything in [~shralex] proposal that I'm
missing. We check for earlier versions of the protocol in learner handler, but
we don't drop the connection. If we do as you suggest, we are just dropping it
explicitly instead of timing out, yes? If so, then I'd rather leave as is,
since the 3.3 follower might end up making progress in the case the leader is
able to form a quorum of 3.4 supporters.
> 3.3 server cannot join 3.4 quorum
> ---------------------------------
>
> Key: ZOOKEEPER-1599
> URL: https://issues.apache.org/jira/browse/ZOOKEEPER-1599
> Project: ZooKeeper
> Issue Type: Bug
> Components: quorum
> Affects Versions: 3.3.6, 3.4.5
> Reporter: Skye Wanderman-Milne
> Assignee: Skye Wanderman-Milne
> Priority: Blocker
> Fix For: 3.4.6
>
> Attachments: ZOOKEEPER-1599.patch
>
>
> When a 3.3 server attempts to join an existing quorum lead by a 3.4 server,
> the 3.3 server is disconnected while trying to download the leader's
> snapshot. The 3.3 server restarts and starts the process over again, but is
> never able to join the quorum.
> 3.3 server log:
> {code}
> 2012-12-07 10:44:34,582 - INFO
> [QuorumPeer:/0:0:0:0:0:0:0:0:2183:Learner@294] - Getting a snapshot from
> leader
> 2012-12-07 10:44:34,582 - INFO
> [QuorumPeer:/0:0:0:0:0:0:0:0:2183:Learner@325] - Setting leader epoch 12
> 2012-12-07 10:44:54,604 - WARN
> [QuorumPeer:/0:0:0:0:0:0:0:0:2183:Follower@82] - Exception when following the
> leader
> java.io.EOFException
> at java.io.DataInputStream.readInt(DataInputStream.java:392)
> at
> org.apache.jute.BinaryInputArchive.readInt(BinaryInputArchive.java:63)
> at
> org.apache.zookeeper.server.quorum.QuorumPacket.deserialize(QuorumPacket.java:84)
> at
> org.apache.jute.BinaryInputArchive.readRecord(BinaryInputArchive.java:108)
> at
> org.apache.zookeeper.server.quorum.Learner.readPacket(Learner.java:148)
> at
> org.apache.zookeeper.server.quorum.Learner.syncWithLeader(Learner.java:332)
> at
> org.apache.zookeeper.server.quorum.Follower.followLeader(Follower.java:75)
> at
> org.apache.zookeeper.server.quorum.QuorumPeer.run(QuorumPeer.java:645)
> 2012-12-07 10:44:54,605 - INFO
> [QuorumPeer:/0:0:0:0:0:0:0:0:2183:Follower@165] - shutdown called
> java.lang.Exception: shutdown Follower
> at
> org.apache.zookeeper.server.quorum.Follower.shutdown(Follower.java:165)
> at
> org.apache.zookeeper.server.quorum.QuorumPeer.run(QuorumPeer.java:649)
> {code}
> 3.4 leader log:
> {code}
> 2012-12-07 10:51:35,178 [myid:2] - INFO
> [WorkerReceiver[myid=2]:FastLeaderElection$Messenger$WorkerReceiver@273] -
> Backward compatibility mode, server id=3
> 2012-12-07 10:51:35,178 [myid:2] - INFO
> [WorkerReceiver[myid=2]:FastLeaderElection@542] - Notification: 3 (n.leader),
> 0x1100000000 (n.zxid), 0x2 (n.round), LOOKING (n.state), 3 (n.sid), 0x11
> (n.peerEPoch), LEADING (my state)
> 2012-12-07 10:51:35,182 [myid:2] - INFO
> [LearnerHandler-/127.0.0.1:37654:LearnerHandler@263] - Follower sid: 3 : info
> : org.apache.zookeeper.server.quorum.QuorumPeer$QuorumServer@262f4873
> 2012-12-07 10:51:35,182 [myid:2] - INFO
> [LearnerHandler-/127.0.0.1:37654:LearnerHandler@318] - Synchronizing with
> Follower sid: 3 maxCommittedLog=0x0 minCommittedLog=0x0
> peerLastZxid=0x1100000000
> 2012-12-07 10:51:35,182 [myid:2] - INFO
> [LearnerHandler-/127.0.0.1:37654:LearnerHandler@395] - Sending SNAP
> 2012-12-07 10:51:35,183 [myid:2] - INFO
> [LearnerHandler-/127.0.0.1:37654:LearnerHandler@419] - Sending snapshot last
> zxid of peer is 0x1100000000 zxid of leader is 0x1200000000sent zxid of db
> as 0x1200000000
> 2012-12-07 10:51:55,204 [myid:2] - ERROR
> [LearnerHandler-/127.0.0.1:37654:LearnerHandler@562] - Unexpected exception
> causing shutdown while sock still open
> java.net.SocketTimeoutException: Read timed out
> at java.net.SocketInputStream.socketRead0(Native Method)
> at java.net.SocketInputStream.read(SocketInputStream.java:150)
> at java.net.SocketInputStream.read(SocketInputStream.java:121)
> at java.io.BufferedInputStream.fill(BufferedInputStream.java:235)
> at java.io.BufferedInputStream.read(BufferedInputStream.java:254)
> at java.io.DataInputStream.readInt(DataInputStream.java:387)
> at
> org.apache.jute.BinaryInputArchive.readInt(BinaryInputArchive.java:63)
> at
> org.apache.zookeeper.server.quorum.QuorumPacket.deserialize(QuorumPacket.java:83)
> at
> org.apache.jute.BinaryInputArchive.readRecord(BinaryInputArchive.java:108)
> at
> org.apache.zookeeper.server.quorum.LearnerHandler.run(LearnerHandler.java:450)
> 2012-12-07 10:51:55,205 [myid:2] - WARN
> [LearnerHandler-/127.0.0.1:37654:LearnerHandler@575] - ******* GOODBYE
> /127.0.0.1:37654 ********
> {code}
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