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https://issues.apache.org/jira/browse/ARTEMIS-908?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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clebert suconic closed ARTEMIS-908.
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> AMQP flow control misses unblock during heavy load
> --------------------------------------------------
>
> Key: ARTEMIS-908
> URL: https://issues.apache.org/jira/browse/ARTEMIS-908
> Project: ActiveMQ Artemis
> Issue Type: Bug
> Components: AMQP
> Reporter: Ulf Lilleengen
> Assignee: Justin Bertram
> Fix For: 2.1.0
>
>
> I have a benchmarking setup with 1 sender and 1 receiver attached to a
> broker. The broker is configured with BLOCK policy when queue is full, and
> I've deliberately set a low global-max-size to trigger this bug.
> While sending messages, I get tons of these in the Artemis log, due to the
> flow control kicking in:
> 10:46:53,673 WARN [org.apache.activemq.artemis.core.server] AMQ222183:
> Blocking message production on address 'myqueue'; size is currently: 105,456
> bytes; max-size-bytes: -1
> 10:46:53,674 INFO [org.apache.activemq.artemis.core.server] AMQ221046:
> Unblocking message production on address 'myqueue'; size is currently:
> 105,456 bytes; max-size-bytes: -1
> However, usually after running the test for 10-30 seconds, the sender is
> suddenly never unblocked and I have to restart the sender to send more
> messages. Every time I attach the sender, I am able to send messages for
> 10~30 seconds until it stops.
> This happens with different clients, and triggers only if it can send
> messages really fast.
> After inspecting the flow control logic in the AMQP implementation, I noticed
> that there is a missing synchronized block when issuing credits in
> AMQPSessionCallback#offerProducerCredit, which is present in
> ProtonServerReceiverContext#flow (if sessionSPI is null).
> Adding a synchronized block with the connection lock to the function passed
> to store.checkMemory() in AMQPSessionCallback#offerProducerCredit (in the
> same way as in ProtonServerReceiverContext#flow), the sender seems to be
> unblocked correctly. I've been able to run the sender and receiver for 5
> minutes without issues so far.
> I'll submit the patch as a github PR.
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