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https://issues.apache.org/jira/browse/ZOOKEEPER-737?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12859119#action_12859119
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Patrick Hunt commented on ZOOKEEPER-737:
----------------------------------------

Yes, there are 2 sets of tests, one for standalone and one for quorum.

FourLetterWordsQuorumTest.java
FourLetterWordsTest.java

However there is a flaw in these tests. They use a socket to do the test, ie 
connect, send, verify resp, close socket

This is not what NC does, it does a connect, send, close write channel, verify 
resp, close socket

and that's why nc fails while everything else was fine.

I'd suggest adding a new set of tests that not only do the old test, but also 
replicate nc. It would also be good to verify
that the connection count stays the same (ie that we don't leak connections).

Should I do the changes for the tests or do you want to?


> some 4 letter words may fail with netcat (nc)
> ---------------------------------------------
>
>                 Key: ZOOKEEPER-737
>                 URL: https://issues.apache.org/jira/browse/ZOOKEEPER-737
>             Project: Zookeeper
>          Issue Type: Bug
>          Components: server
>    Affects Versions: 3.3.0
>            Reporter: Patrick Hunt
>            Assignee: Mahadev konar
>            Priority: Blocker
>             Fix For: 3.3.1, 3.4.0
>
>         Attachments: ZOOKEEPER-737.patch
>
>
> nc closes the write channel as soon as it's sent it's information, for 
> example "echo stat|nc localhost 2181"
> in general this is fine, however the server code will close the socket as 
> soon as it receives notice that nc has
> closed it's write channel. if not all the 4 letter word result has been 
> written back to the client yet, this will cause
> some or all of the result to be lost - ie the client will not see the full 
> result. this was introduced in 3.3.0 as part
> of a change to reduce blocking of the selector by long running 4letter words.
> here's an example of the logs from the server during this
> echo -n stat | nc localhost 2181
> 2010-04-09 21:55:36,124 - INFO  
> [NIOServerCxn.Factory:0.0.0.0/0.0.0.0:2181:nioservercnxn$fact...@251] - 
> Accepted socket connection from /127.0.0.1:42179
> 2010-04-09 21:55:36,124 - INFO  
> [NIOServerCxn.Factory:0.0.0.0/0.0.0.0:2181:nioserverc...@968] - Processing 
> stat command from /127.0.0.1:42179
> 2010-04-09 21:55:36,125 - WARN  
> [NIOServerCxn.Factory:0.0.0.0/0.0.0.0:2181:nioserverc...@606] - 
> EndOfStreamException: Unable to read additional data from client sessionid 
> 0x0, likely client has closed socket
> 2010-04-09 21:55:36,125 - INFO  
> [NIOServerCxn.Factory:0.0.0.0/0.0.0.0:2181:nioserverc...@1286] - Closed 
> socket connection for client /127.0.0.1:42179 (no session established for 
> client)
> [ph...@gsbl90850 zookeeper-3.3.0]$ 2010-04-09 21:55:36,126 - ERROR 
> [Thread-15:nioserverc...@422] - Unexpected Exception: 
> java.nio.channels.CancelledKeyException
>       at sun.nio.ch.SelectionKeyImpl.ensureValid(SelectionKeyImpl.java:55)
>       at sun.nio.ch.SelectionKeyImpl.interestOps(SelectionKeyImpl.java:59)
>       at 
> org.apache.zookeeper.server.NIOServerCnxn.sendBuffer(NIOServerCnxn.java:395)
>       at 
> org.apache.zookeeper.server.NIOServerCnxn$SendBufferWriter.checkFlush(NIOServerCnxn.java:907)
>       at 
> org.apache.zookeeper.server.NIOServerCnxn$SendBufferWriter.flush(NIOServerCnxn.java:945)
>       at java.io.BufferedWriter.flush(BufferedWriter.java:236)
>       at java.io.PrintWriter.flush(PrintWriter.java:276)
>       at 
> org.apache.zookeeper.server.NIOServerCnxn$2.run(NIOServerCnxn.java:1089)
> 2010-04-09 21:55:36,126 - ERROR [Thread-15:nioservercnxn$factor...@82] - 
> Thread Thread[Thread-15,5,main] died
> java.nio.channels.CancelledKeyException
>       at sun.nio.ch.SelectionKeyImpl.ensureValid(SelectionKeyImpl.java:55)
>       at sun.nio.ch.SelectionKeyImpl.interestOps(SelectionKeyImpl.java:64)
>       at 
> org.apache.zookeeper.server.NIOServerCnxn$SendBufferWriter.wakeup(NIOServerCnxn.java:927)
>       at 
> org.apache.zookeeper.server.NIOServerCnxn$SendBufferWriter.checkFlush(NIOServerCnxn.java:909)
>       at 
> org.apache.zookeeper.server.NIOServerCnxn$SendBufferWriter.flush(NIOServerCnxn.java:945)
>       at java.io.BufferedWriter.flush(BufferedWriter.java:236)
>       at java.io.PrintWriter.flush(PrintWriter.java:276)
>       at 
> org.apache.zookeeper.server.NIOServerCnxn$2.run(NIOServerCnxn.java:1089)

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