If max_prefetch is 0 , FlowControllingBlockingQueue will eventually suspend the
message flow
--------------------------------------------------------------------------------------------
Key: QPID-2074
URL: https://issues.apache.org/jira/browse/QPID-2074
Project: Qpid
Issue Type: Bug
Components: Java Client
Affects Versions: 0.5
Reporter: Rajith Attapattu
Assignee: Rajith Attapattu
Fix For: 0.6
The FlowControllingBlockingQueue will suspend and unsuspend the message flow,
on reaching the high and low watermarks respectively.
In 0-10 code path, if the max_prefetch is set to 0, the above class could
irrevocably suspend the message flow under the following circumstances.
1. The _count starts at zero and we receive a message. The _count is
incremented to 1 (the high water mark check passes as high-watermark is zero).
2. If the message is taken from the queue the count will be reduced to zero
(fails the low water mark check) .
3. The client waits for the next message inside take() and gets notified once a
message is put on the queue inside the add(). However the code block that
decrements _count inside the take() method could execute before the code block
that increments _count inside the take()
4. If the above happened the decrement (in take()) will bring _count to -1 and
the increment (in add()) will bring the _count to zero, hence will fail the
high water mark check. This will trigger a session suspend which results in
sending a message-stop in 0-10 code path.
5. So even if there are more messages on the brokers queue, and the client
calling receive() and sending 1 message credit, the broker will not send any
messages to the client due to lack of byte credits as all message/byte credits
was wiped out by the previous message-stop. This will make the JMS client block
on receive() even when there is messages in the queue.
--
This message is automatically generated by JIRA.
-
You can reply to this email to add a comment to the issue online.
---------------------------------------------------------------------
Apache Qpid - AMQP Messaging Implementation
Project: http://qpid.apache.org
Use/Interact: mailto:[email protected]
