Well, I seem to have fixed it... I completely overlooked that the
default for the prefetch is actually larger than 1. Setting it to 1
fixes the problem. Still it seems to be a bit of a waste that several
newly connected consumers can be idle while because a "old" one that is
processing, is actually "locking" the other messages.
Best regards,
Arjen
On 8-6-2009 15:40, Arjen van der Meijden wrote:
Hello list,
In a somewhat complicated set of consumption-processing, I have three
queues. One to indicate a new job, which is consumed by a single
long-running consumer that sends messages to a second queue.
That second queue is consumed by four consumers that kill themselves
after having processed a (few) message(s). After each message from the
second queue is processed, they're send to a third queue which has two
similar consumers.
As soon as such a consumer exits, a control process starts a new
consumer, to have a fixed amount of consumers.
The jobs for the initial queue are issued in batches, so there can be a
burst of about 150 messages, resulting in a burst in the second queue.
As soon as those second-queue-consumers exit however, they don't consume
much messages. Most of the time it seems that only one is actually doing
any work and the other three are idle, even if the queue has more than
100 messages. The same holds for the third-queue-consumers.
It seems to have to do with the fact that those consumers actually
subscribe to the queue after the messages have been produced. Obviously,
I want them to start consuming a message as soon as they connect.
All message production and consumption is via Stomp in PHP and the
ActiveMQ is a 5.2.0-version with mostly a default configuration. I have
tried to see if subscribing using the headers 'activemq.retroactive' and
'activemq.dispatchAsync' set to 'true' make any difference, but that
doesn't seem to do anything.
Anyone knows what's going on and how to fix it?
Best regards,
Arjen
