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From "Robbie Gemmell (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (DISPATCH-1090) Transfer/Disposition(state=release) loop forms when application disconnects abruptly from brokered queue until link credit is exhausted.
Date Mon, 10 Sep 2018 14:47:00 GMT

    [ https://issues.apache.org/jira/browse/DISPATCH-1090?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16609311#comment-16609311

Robbie Gemmell commented on DISPATCH-1090:

I may be misunderstanding, I don't know the router code, but reading the test it seems like
the change operates only after a message arrives that is undeliverable? That could prevent
a release->send loop forming until the credit is used in some cases, but it seems like
in others it wouldn't be as effective as it could be?

There is obviously a race here in that even if the drain were performed immediately when the
last receiver went away the sender might already have put lots of messages in flight using
credit it had. However it seems a little odd potentially leaving the sender with that credit
for an unknown amount of time until they use it to send something. In that regard, its just
as likely a large number of small messages could end up being sent later if they become available
at the sender and end up being sent+released.

One complication might be address-specific links vs anonymous sender links, though it isn't
clear to me whether they are handled any different (again, don't know the router code). In
some ways makes sense, stops them sending lots to the address, but in other ways could be
questionable as the anonymous link then cant sent to other addresses either.

In any case, I'd perhaps say the tests could do with expanding to ensure credit is restored
at the appropriate time and in the expected amount. Another useful case to test might be when
a new receiver becomes available before the sender has completed draining after the original
receivers went away. Distinct drain attempts cant really be correlated without allowing them
to complete before then flowing more credit or attempting another drain, and failing to account
for that might leave you thinking a link has credit when it doesnt.

> Transfer/Disposition(state=release) loop forms when application disconnects abruptly
from brokered queue until link credit is exhausted.
> ----------------------------------------------------------------------------------------------------------------------------------------
>                 Key: DISPATCH-1090
>                 URL: https://issues.apache.org/jira/browse/DISPATCH-1090
>             Project: Qpid Dispatch
>          Issue Type: Bug
>         Environment: Version                          1.3.0-SNAPSHOT
>  (30ff7ff1d54b8f280b36f76dc8c340cb4c88567b)
>            Reporter: Keith Wall
>            Assignee: Ganesh Murthy
>            Priority: Major
>             Fix For: 1.4.0
>         Attachments: DISPATCH-1090_dispatch_server.log
> I have configured a single Dispatch Router instance to route messages through a broker
queue (i.e. following section 7.2.5 of the [docs|https://qpid.apache.org/releases/qpid-dispatch-1.2.0/user-guide/index.html#routing-messages-through-broker]).
> The application does the following:
> # Forms a sending links to the queue, sends a single message then disconnects.
> # Forms a receiving link to the same queue, receives the message without settling then
abruptly terminates the program.
> Inspecting the protocol trace, I see that after the Dispatch Router has sent a {{Disposition
state=modified}} for the message that was held by the application when it terminated, a {{Transfer}}/{{Disposition
state=release}} loop forms between the Dispatch Router and Broker until the link credit is
> Protocol trace attached to this issue demonstrates the problem.
> Dispatch Router was configured by the following commands:
> {noformat}
> qdmanage create --type org.apache.qpid.dispatch.connector host=oslo.local port=5672 name=artemis-broker
> qdmanage create --type org.apache.qpid.dispatch.router.config.autoLink addr=queue direction=in
> qdmanage create --type org.apache.qpid.dispatch.router.config.autoLink addr=queue direction=out
> qdmanage create --type=org.apache.qpid.dispatch.router.config.address pattern=queue waypoint=true
> {noformat}

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