On 07/16/2012 12:04 PM, Sitapati das / Joshua J Wulf wrote:
Hi, I noticed that if I create an autodeleting queue and it gets
auto-deleted, my attempts to send to it don't cause an exception, and my
messages seem to disappear into the ether. Is that expected behaviour?
Expected by whom?!
It is an unfortunate aspect of the model in pre-1.0 AMQP, where you send
messages to an exchange, never a queue. The default exchange is a little
trick to work around that, but you are still sending to an exchange.
While it is an error to send to a non-existent exchange, it is not an
error to send to an exchange that is not able to route the message to a
queue.
In the messaging API we try to work around that by checking the queue
exists when you create your sender. However once created, we don't want
to check for every message just to handle this sort of case.
We could in theory make use of rejects for this case, but haven't done so.
I'm using the python client. Here's a minimal test case that reproduces the
behaviour:
import sys
from qpid.messaging import *
connection=Connection("localhost:5672")
connection.open()
try:
session=connection.session()
tx=session.sender("test-queue; {create:always,
node:{x-declare:{auto-delete:True}}}")
tx.send("test message!")
x = raw_input("Press Enter to continue")
tx.send("test message 2")
except MessagingError, m:
print m
connection.close()
When the program pauses for keyboard input, I subscribe and unsubscribe
using drain -c 0 test-queue in another window. This causes the queue to
auto-delete.
I would expect an exception to be thrown when I try to send the second test
message, but it isn't.
Is this a bug? Am I doing something wrong?
The auto-delete is also a little unintuitive unless you are very
familiar with the pre-1.0 AMQP model. In this case the queue will be
deleted, as you point out, when the consumer count drops back to 0, even
though the queue is still in a real sense 'in-use' by the sender.
Do you have a use case that requires auto-deletion of a shared queue? If
so perhaps some more detail on that could help making suggestions on how
best to handle it.
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