Viktor Horvath created QPID-6740:
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Summary: Message not delivered after "empty" exception
Key: QPID-6740
URL: https://issues.apache.org/jira/browse/QPID-6740
Project: Qpid
Issue Type: Bug
Components: C++ Broker, Python Client
Affects Versions: 0.32
Environment: CentOS 7.1
qpid (C++) 0.32, qpid-python 0.32
Reporter: Viktor Horvath
If this is not a bug, the documentation might need an update, as I'm not aware
of what I did wrong :-)
Here is a test case, you will need two ipython consoles.
{code:title=console 1}
from qpid.messaging import Connection
session = Connection.establish('amqp://127.0.0.1').session()
sender = session.sender(
'mytestqueue; {create: always, node: {durable: True, type: queue}}')
cleaner = session.receiver('mytestqueue')
cleaner.fetch(timeout=0) # will raise a qpid.messaging.exceptions.Empty
{code}
(The receiver is named _cleaner_ because it is only supposed to "free" the
queue from any old messages.)
{code:title=console 2}
from qpid.messaging import Connection
session = Connection.establish('amqp://127.0.0.1').session()
receiver = session.receiver('mytestqueue')
receiver.fetch()
{code}
Back to the first console:
{code:title=console 1}
sender.send({'msg': 'test'})
{code}
*This message does not arrive at the second console. The receiver.fetch() still
blocks.*
I have the following observations about this situation:
# One workaround is to call cleaner.close(), the blocking receiver will
immediately return the message.
# Another workaround is to specify a time-out in the receiver.fetch() call
(test it with timeout=60). The message will be returned, though only at the end
of the time-out!
# Sending a second message will result in immediate delivery of the first
message.
# Once the situation is unblocked, you have to start anew in order to
experience the blocking situation again. Don't forget to call
session.acknowledge() before ending the console 2, or use a fresh queue.
# The problem only manifests itself when receiver.fetch() starts before the
message is sent.
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