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From "Martin Ritchie (JIRA)" <qpid-...@incubator.apache.org>
Subject [jira] Commented: (QPID-942) Introduce client flow control and broker overflow protection
Date Thu, 08 Oct 2009 12:24:31 GMT

    [ https://issues.apache.org/jira/browse/QPID-942?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12763466#action_12763466
] 

Martin Ritchie commented on QPID-942:
-------------------------------------

Hi Rob, would be cleaner for the test to reuse the QpidTestCase setSystemProperty option,
or setTestClientSystemProperty if the property has an undesired impact on the broker. This
will ensure that the value get correctly reset at the end of the test. Currently a failure
of your tests will leave the test value set.

> Introduce client flow control and broker overflow protection
> ------------------------------------------------------------
>
>                 Key: QPID-942
>                 URL: https://issues.apache.org/jira/browse/QPID-942
>             Project: Qpid
>          Issue Type: New Feature
>          Components: Java Broker, Java Client
>            Reporter: Marnie McCormack
>            Assignee: Rob Godfrey
>             Fix For: 0.6
>
>
> Certainly the Java, and probably the other clients do not obey flow-control commands
from the broker. The Java broker never sends them to clients either. This is in the 0-8 spec.
so not fully AMQP compliant without it. 
> Client Work
> -------------------
> Flow control to be implemented in clients. The clients must also have buffer limiting
in place prior to this, or flow-controlling a client will only shift OOMEs from the broker
to the clients. Bounded buffers plus back-pressure from the broker will should ultimately
lead to the 'send' method blocking once the system as a whole is completely saturated. This
may mean that the broker gets a needed opportunity to chew its way through the back-log, resulting
in healthy throughputs under saturation. 
> Broker Work
> ------------------
> A strategy for deciding when to flow control clients from the broker needs to be decided
upon. Flow-control has per-connection granularity, which makes deciding when to do it on a
per route basis awkward. Flow-control may be triggered by: 
> 1. The broker being low on memory globally across the message store and all queues. 
> 2. A client attempting to publish to a queue that is beyond its max-depth. 
> 3. Based on history of destinations a client usually publishes to (or has published to),
flow-control client if one of them is beyond max-depth. 
> A well-conditioned application will not experience 'send' blocking, except under exceptional
loads, whereupon it will act as a safety valve to prevent either clients or broker from throwing
OOME. The other scenario that may cause back-logs, is slow consumers without TTL. 
> No time estimate for this yet, as its a fairly large piece of work, and not yet decided
exactly how its to be done. Need a design proposal before starting work, to be reviewed by
the qpid-dev group.

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