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https://issues.apache.org/activemq/browse/AMQCPP-315?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=61566#action_61566
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Helen Huang commented on AMQCPP-315:
------------------------------------
I have looked at the code for IdGenerator again and I think I might understand
what is going on.
std::string IdGenerator::generateId() const {
std::string result;
StaticData& statics = IdGenerator::getClassStaticData();
synchronized( &statics.mutex ) {
if( seed.empty() ) {
if( prefix.empty() ) {
this->seed = std::string( "ID:" ) + statics.hostname +
statics.UNIQUE_STUB + Long::toString(
statics.instanceCount++ ) + ":";
} else {
this->seed = prefix + statics.UNIQUE_STUB + Long::toString(
statics.instanceCount++ ) + ":";
}
}
result = this->seed + Long::toString( this->sequence++ );
}
return result;
}
The second line in this function can be accessed by multiple threads:
StaticData& statics = IdGenerator::getClassStaticData();
The definition for IdGenerator::getClassStaticData() is
IdGenerator::StaticData& IdGenerator::getClassStaticData() {
static IdGenerator::StaticData statics;
return statics;
}
The constructor of IdGenerator::StaticData calls InetAddress::getLocalHost() to
get the host name.
It seems that this constructor can be entered by multiple threads at the same
time and mess up the apr get host name functionality.
I have fixed the problem by making the "statics" variable a member of
IdGenerator, and by adding the statement of "IdGenerator::StaticData
IdGenerator::statics;" to IdGenerator.cpp.
Attached please find the modified code in IdGenerator.h and .cpp. Hope this fix
is acceptable to you :)
Thanks!
> Advisory messages do not work with multiple listeners
> -----------------------------------------------------
>
> Key: AMQCPP-315
> URL: https://issues.apache.org/activemq/browse/AMQCPP-315
> Project: ActiveMQ C++ Client
> Issue Type: Bug
> Affects Versions: 3.2.2
> Environment: Windows, ActiveMQ 5.3.1
> Reporter: Helen Huang
> Assignee: Timothy Bish
> Attachments: activemq.log, AdvisoryMessageListener2.zip,
> vs2005-build.zip
>
>
> We found that the advisory messages do not work as expected when there are
> multiple consumers listening to the same advisory topics.
> We have three applications, AdvisoryMessageListener, MessageListener, and
> MessageSender.
> AdvisoryMessageListener listens to the following two topics:
> ActiveMQ.Advisory.Consumer.Topic.cpp.itemLookup
> ActiveMQ.Advisory.Producer.Topic.cpp.itemLookup
> MessageListener listens to topic: cpp.itemLookup
> MessageSender sends messages to topic: cpp.itemLookup
> If there is only one instance of AdvisoryMessageListener , then everything
> work fine. We can get the advisory messages when we start/shut down
> MessageListener or MessageSender . However, when we start a second instance
> of AdvisoryMessageListener , it seems to knock out the existing connection of
> the first AdvisoryMessageListener. The first instance can no longer receive
> any advisory messages after that.
> This problem could be related to the problem reported in jira item
> "AMQCPP-314 Starting app with Com using cms destroys connection of other app.
> New problem with recent lib version". However in our problem, we do not have
> any COM layers.
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