Hi,
We have encountered a problem with an application using QPid 0.22/APQP
0.10 with the C++ messaging API, which could be caused by creation of an
excessive number of threads. This might not be related to QPid, and the
issue may not even be threading in this application (the problem occurs
once every blue moon, so it's a bit hard to test theories), but in order
to get a clear picture of the situation, it would be good to know what
threads QPid creates, and if there are any issues with threading. Some
questions:
* When exactly does QPid create a new thread?
* Are there any known situations where one might end up with lots of
runaway threads?
* Do I have to do anything specific e.g. after a communication error
in order to make sure old threads go away?
I have one connection object with one session which in turn has one
sender and two receivers (for two different queues.) Whenever an
exception occurs, I close down the connection using connection.close(),
and reset everything else by assigning a default-constructed object, as in
session=qpid::messaging::Session();
sender=qpid::messaging::Sender();
etc.
I then (later) try to reopen using a construct like
if(!connection.isOpen())
connection.open();
if(session.isNull())
session=connection.createSession();
if(receiver.isNull())
receiver=session.createReceiver(<address>);
if(receiver2.isNull())
receiver2=session.createReceiver(<address>);
if(sender.isNull())
sender=session.createSender(<address>);
This code is executed periodically, and is also what takes care of
first-time creation after startup. This is done within a try ... catch
block.
The actual problem I'm talking about is that a pthread_create() call
used for something unrelated will sometimes fail with EAGAIN.
An information anyone might have about the threading behaviour of QPid
would be helpful.
TIA,
- Toralf
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