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From "Hiram Chirino (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (APLO-206) Load balance of job queues when 'credit:1,0' is used on the consumer.
Date Wed, 23 May 2012 02:24:40 GMT

     [ https://issues.apache.org/jira/browse/APLO-206?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Hiram Chirino updated APLO-206:
-------------------------------

    Summary: Load balance of job queues when 'credit:1,0' is used on the consumer.  (was:
Load balance of job queues)
    
> Load balance of job queues when 'credit:1,0' is used on the consumer.
> ---------------------------------------------------------------------
>
>                 Key: APLO-206
>                 URL: https://issues.apache.org/jira/browse/APLO-206
>             Project: ActiveMQ Apollo
>          Issue Type: Improvement
>          Components: apollo-broker, apollo-openwire, apollo-stomp
>    Affects Versions: 1.3
>            Reporter: José Micó
>             Fix For: 1.4
>
>
> I wish to have load balanced job queues, like in ActiveMQ (copied and pasted):
> "A queue implements load balancer semantics. A single message will be received by exactly
one consumer. If there are no consumers available at the time the message is sent it will
be kept until a consumer is available that can process the message. If a consumer receives
a message and does not acknowledge it before closing then the message will be redelivered
to another consumer. A queue can have many consumers with messages load balanced across the
available consumers."
> For example, suppose that I send tree jobs (j1, j2, j3) to a queue with 2 consumers (c1,c2).
> The first job takes 10 seconds to complete, jobs 2 and 3 takes only 1 second.
> Consumers are using 'client' ack, with credit:1,0 in order to receive only one job at
the time.
> The desired behaviour of consumers is:
> [ 21:30:00 ][ c1 ] Got job 1
> [ 21:30:00 ][ c2 ] Got job 2
> [ 21:30:01 ][ c2 ] Ack job 2, now idle
> [ 21:30:01 ][ c2 ] Got job 3
> [ 21:30:02 ][ c2 ] Ack job 3, now idle
> [ 21:30:10 ][ c1 ] Ack job 1, now idle
> But currently, Apollo does:
> [ 21:30:00 ][ c1 ] Got job 1
> [ 21:30:00 ][ c2 ] Got job 2
> [ 21:30:01 ][ c2 ] Ack job 2, now idle   (!) c2 is idle but does not gets job 3 
> [ 21:30:10 ][ c1 ] Ack job 1, now idle
> [ 21:30:10 ][ c1 ] Got job 3
> [ 21:30:11 ][ c1 ] Ack job 3, now idle
> Seems that jobs are assigned in a round-robin fashion at the moment of being received
by the broker.
> If in this example I send 9 jobs of 1 second (instead of 2), consumer #1 gets 5 and consumer
#2 gets the remaining 5, when the optimum would be to send the 9 fast jobs to consumer #2
while consumer #1 is processing the slow one. I know that using 'client' ack with credit:1,0
is suboptimal from broker perspective, but is the optimal way to balance jobs between workers.
> Besides the underutilization of resources, the main problem is that if a consumer takes
too much time to process a job (say, due to a DB lock) it may block the processing of a bunch
of jobs already assigned to it.
> ...
> BTW, impressive piece of work!!! I really impressed by the completeness of features,
and how well Apollo behaved when I overloaded it with stress tests :)

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