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Posted to issues@activemq.apache.org by "ASF GitHub Bot (JIRA)" <ji...@apache.org> on 2016/05/11 11:07:13 UTC
[jira] [Commented] (ARTEMIS-46) AMQP interop: Active broker does
not respect the "drain" flag.
[ https://issues.apache.org/jira/browse/ARTEMIS-46?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15279937#comment-15279937 ]
ASF GitHub Bot commented on ARTEMIS-46:
---------------------------------------
GitHub user mtaylor opened a pull request:
https://github.com/apache/activemq-artemis/pull/514
ARTEMIS-46 Adds AMQP Drain Support
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/mtaylor/activemq-artemis AMQPDrainImpl
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/activemq-artemis/pull/514.patch
To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:
This closes #514
----
commit 54752a9cedcceef9715345730eae4766be2c8458
Author: Martyn Taylor <mt...@redhat.com>
Date: 2016-05-10T13:55:20Z
ARTEMIS-46 Adds AMQP Drain Support
----
> AMQP interop: Active broker does not respect the "drain" flag.
> --------------------------------------------------------------
>
> Key: ARTEMIS-46
> URL: https://issues.apache.org/jira/browse/ARTEMIS-46
> Project: ActiveMQ Artemis
> Issue Type: Bug
> Components: AMQP
> Affects Versions: 1.0.0
> Reporter: Alan Conway
> Priority: Minor
> Fix For: 1.3.0
>
>
> The drain flag on the AMQP flow performative allows a client to request confirmation that it has received the last available message that it has credit to receive.
> To reproduce using the qpid-send, qpid-receive clients from http://svn.apache.org/repos/asf/qpid/trunk/qpid/. Create a JMS queue 'foo' on the active broker then run:
> $ qpid-send -a jms.queue.foo -b localhost:5455 --content-string XXX --connection-options='{protocol:amqp1.0}'
> $ qpid-receive -a jms.queue.foo -b localhost:5455 --connection-options='{protocol:amqp1.0}' --log-enable trace+:Protocol
> qpid-receive hangs, the last line of output is:
> 2014-11-24 15:15:46 [Protocol] trace [58e8ee08-0f33-426b-b77a-450f7c3d976c]: 0 -> @flow(19) [next-incoming-id=2, incoming-window=2147483647, next-outgoing-id=0, outgoing-window=0, handle=0, delivery-count=1, link-credit=1, drain=true]
> This shows that qpid-receive sent a flow with drain=true but never received a response.
> Why is this important? Without the drain flag it is impossible for a client to implement the simple behavior "get the next message" correctly. The flow response tells the client immediately "there are no more messages available for you". Without it the client can only use a timeout which is unreliable (if too short the client may give up while the message is in flight) and inefficient (if too long the client will wait needlessly for messages that the broker knows are not presently available)
> The spec 2.6.7 is a little ambiguous about whether this is a SHOULD or a MUST behavior but without it it is impossible to implement the use cases described in the following section.
> AMQP 1.0 specification 2.7.6
> drain
> The drain flag indicates how the sender SHOULD behave when insufficient messages are available to consume the current link-credit. If set, the sender will (after sending all available messages) advance the delivery-count as much as possible, consuming all link-credit, and send the flow state to the receiver. Only the receiver can independently modify this field. The sender's value is always the last known value indicated by the receiver.
> If the link-credit is less than or equal to zero, i.e., the delivery-count is the same as or greater than the delivery-limit, a sender MUST NOT send more messages. If the link-credit is reduced by the receiver when transfers are in-flight, the receiver MAY either handle the excess messages normally or detach the link with a transfer-limit-exceeded error code.
> Figure 2.40: Flow Control
> +----------+ +----------+
> | Sender |---------------transfer------------>| Receiver |
> +----------+ +----------+
> \ / <----------------flow--------------- \ /
> +------+ +------+
> |
> |
> |
> if link-credit <= 0 then pause
>
> If the sender's drain flag is set and there are no available messages, the sender MUST advance its delivery-count until link-credit is zero, and send its updated flow state to the receiver.
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