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https://issues.apache.org/jira/browse/ZOOKEEPER-1197?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13467265#comment-13467265
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Skye Wanderman-Milne commented on ZOOKEEPER-1197:
-------------------------------------------------
Based on the second code snippet in the link Patrick found, I've written an
alternate patch (ZOOKEEPER-1197_shutdown.patch) that waits for the client to
shutdown the input connection before closing the socket.
I've managed to reproduce the problem locally for testing:
0. My base setup: trunk zk checkout, Ubuntu 12.04, Oracle Java 6, no fancy
zoo.cfg
1. I wrote a new 4lw, "long", that prints 100k '.'s followed by a '!' (so you
can see if it's truncated). See long_4lw.patch.
2. Slow down your localhost connection: sudo tc qdisc add dev lo root netem
delay 1000ms
(To undo this command: sudo tc qdisc del dev lo root)
3. Start a zk server with ./bin/zkServer.sh start
4. Send a long command: echo long | nc localhost 2181 (I've also been using
FourLetterWordMain)
This should fill your terminal with dots, but shouldn't end with a !. If you
see the !, the output wasn't truncated (i.e., you haven't hit the bug).
The new patch fixes the bug with this setup. Camille's patch also fixes it,
although I do not fully understand how :) Since Camille reports having problems
even after applying her patch (which I could not reproduce), this patch
probably needs further testing as well. It would also be useful to test with a
variety of clients (it sounds like this is the standard way to close a TCP
connection, but I'm not positive every client will shut down the connection
correctly).
> Incorrect socket handling of 4 letter words for NIO
> ---------------------------------------------------
>
> Key: ZOOKEEPER-1197
> URL: https://issues.apache.org/jira/browse/ZOOKEEPER-1197
> Project: ZooKeeper
> Issue Type: Bug
> Components: server
> Affects Versions: 3.3.3, 3.4.0
> Reporter: Camille Fournier
> Assignee: Camille Fournier
> Priority: Critical
> Fix For: 3.5.0
>
> Attachments: long_4lw.patch, ZOOKEEPER-1197.patch,
> ZOOKEEPER-1197_shutdown.patch
>
>
> When transferring a large amount of information from a 4 letter word,
> especially in interactive mode (telnet or nc) over a slower network link, the
> connection can be closed before all of the data has reached the client. This
> is due to the way we handle nc non-interactive mode, by cancelling the
> selector key.
> Instead of cancelling the selector key for 4-letter-words, we should instead
> flag the NIOServerCnxn to ignore detection of a close condition on that
> socket (CancelledKeyException, EndOfStreamException). Since the 4lw will
> close the connection immediately upon completion, this should be safe to do.
> See ZOOKEEPER-737 for more details
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