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https://issues.apache.org/jira/browse/QPID-4171?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13424537#comment-13424537
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Keith Wall edited comment on QPID-4171 at 7/29/12 1:02 PM:
-----------------------------------------------------------
#addFuture() is used by #enqueue() to arrange for the postTransactionAction to
be executed as each store transaction is completed asynchronously by the
commit-thread.
An optimisation in #addFuture means that an enqueue can 'jump-the-queue', and
be enqueued before others that are already waiting in the future recorder list.
A problematic sequence would be:
1) Message 1 arrives from sender
2) AsyncAutoCommitTransaction.enqueue called, but as commit thread is running
behind, so its enqueue action joins list of the future recorder.
3) Messages 2 arrives from sender
4) BDB commit thread catches up the backlog
5) AsyncAutoCommitTransaction.enqueue called but as the StoreFuture is already
completed, its enqueue action is executed immediately so Message 2 is enqueued.
6) AMQProtocolEngine#complete calls receiveComplete() so Message 1 enqueue
action is called.
7) Message 2 will be delivered to a Consumer before Message 1.
{code}
private void addFuture(final StoreFuture future, final Action action)
{
if(action != null)
{
if(future.isComplete())
{
action.postCommit();
}
else
{
_futureRecorder.recordFuture(future, action);
}
}
}
{code}
was (Author: k-wall):
#addFuture() is used by #enqueue() to arrange for the postTransactionAction
to be executed as each store transaction is completed asynchronously by the
commit-thread.
An optimisation in #addFuture means that an enqueue can 'jump-the-queue', and
be enqueued before others that are already waiting in the future recorder list.
A problematic sequence would be:
1) Message 1 arrives from sender
2) AsyncAutoCommitTransaction.enqueue called, but as commit thread is running
behind, so its enqueue action joins list of the future recorder.
3) Messages 2 arrives from sender
4) BDB commit thread catches up the backlog
5) AsyncAutoCommitTransaction.enqueue called but as the StoreFuture is already
completed, its enqueue action is executed immediately so Message 2 is enqueued.
6) AMQProtocolEngine#complete calls receiveComplete() so Message 1 enqueue
action is called.
{code}
private void addFuture(final StoreFuture future, final Action action)
{
if(action != null)
{
if(future.isComplete())
{
action.postCommit();
}
else
{
_futureRecorder.recordFuture(future, action);
}
}
}
{code}
> Messages from a non-transactional session can be enqueued out of order
> ----------------------------------------------------------------------
>
> Key: QPID-4171
> URL: https://issues.apache.org/jira/browse/QPID-4171
> Project: Qpid
> Issue Type: Bug
> Components: Java Broker
> Affects Versions: 0.16, 0.18, 0.19
> Reporter: Keith Wall
> Assignee: Keith Wall
>
> A defect in AsyncAutoCommitTransaction means that occasionally messages
> delivered by a non-transactional JMS are seen to be enqueued out-of-order and
> therefore delivered to a consumer out of the expected order.
> It is this problem that underlies QPID-4014, although as I think this problem
> is wider than ConflationQueues, I am raising this separately.
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