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From "Keith Wall (JIRA)" <j...@apache.org>
Subject [jira] [Resolved] (QPID-3498) Broker race condition means that it tries to respond before IoSender thread is running
Date Wed, 21 Sep 2011 16:05:13 GMT

     [ https://issues.apache.org/jira/browse/QPID-3498?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel

Keith Wall resolved QPID-3498.

    Resolution: Fixed

Committed change so that sender thread is always started before receiver thread, so this problem
can no longer occur. 

Also added a defensive check to IoSender#send to make diagnosis more obvious should this problem
ever regress.

> Broker race condition means that it tries to respond before IoSender thread is running
> --------------------------------------------------------------------------------------
>                 Key: QPID-3498
>                 URL: https://issues.apache.org/jira/browse/QPID-3498
>             Project: Qpid
>          Issue Type: Bug
>          Components: Java Broker
>            Reporter: Keith Wall
>            Assignee: Keith Wall
>             Fix For: 0.13
> Since the removal of Mina from the transport layer, we've been seeing sporadic failures
from the java-mms-spawn.0-9-1 profile on an old slow CI server.
> Tests are failing with the following exception whilst the client is attempting to negotiate
downwards from 0-10 to 0-9-1 protocol during connection:
> {code}
> main 2011-09-21 14:27:09,139 INFO [apache.qpid.client.AMQConnection] Unable to connect
to broker at tcp://localhost:15672
> org.apache.qpid.AMQException: Cannot connect to broker: connect() aborted [error code
200: reply success]
>         at org.apache.qpid.client.AMQConnectionDelegate_0_10.makeBrokerConnection(AMQConnectionDelegate_0_10.java:218)
>         at org.apache.qpid.client.AMQConnection.makeBrokerConnection(AMQConnection.java:565)
>         at org.apache.qpid.client.AMQConnection.<init>(AMQConnection.java:351)
>         at org.apache.qpid.client.AMQConnectionFactory.createConnection(AMQConnectionFactory.java:132)
>         at org.apache.qpid.client.AMQConnectionFactory.createConnection(AMQConnectionFactory.java:111)
>         at org.apache.qpid.test.utils.QpidBrokerTestCase.getConnection(QpidBrokerTestCase.java:1056)
>         at org.apache.qpid.test.unit.basic.LargeMessageTest.setUp(LargeMessageTest.java:52)
>         at junit.framework.TestCase.runBare(TestCase.java:125)
>         at org.apache.qpid.test.utils.QpidBrokerTestCase.runBare(QpidBrokerTestCase.java:238)
>         at junit.framework.TestResult$1.protect(TestResult.java:106)
>         at junit.framework.TestResult.runProtected(TestResult.java:124)
> {code}
> Analysis has shown that when the problem occurs, the broker tries to write the highest
supported protocol version number to the wire, but these bytes never make it to the wire (see
MultiVersionProtocolEngine#received() lines 409-414).   The reason for this is a race condition:
there is an unlucky timing where the broker may begin responding to incoming frames *before*
it has started the IoSender thread. 

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