ANN: Habari Client for RabbitMQ - Delphi and Free Pascal STOMP client

[michael...@gmx.net]

21 February 2015 - Habarisoft released version 2.1 of Habari Client for 
RabbitMQ, a Delphi and Free Pascal STOMP client library for the RabbitMQ 
message broker. This maintenance release includes documentation updates 
and bug fixes, and many minor improvements.

Full release notes:
https://mikejustin.wordpress.com/2015/02/20/habari-client-libraries-release-2015-02/

Home page:
https://www.habarisoft.com/habari_rabbitmq.html

Regards,
-- 
Michael Justin

[Michael Klishin]

Michael,

Thank you.

I've noticed that the feature matrix on your site claims that RabbitMQ does not support
message priorities.

It will out of the box in 3.5.0 and there is a plugin [1] for that for 3.4.x releases.

1. https://github.com/rabbitmq/rabbitmq-priority-queue
--
MK

Staff Software Engineer, Pivotal/RabbitMQ

[michael...@gmx.net]

Hello Michael, many thanks for the information! I have updated the feature matrix, some minor changes in the library and its documentation will follow soon.

[michael...@gmx.net]

Hi Michael,

does the current version of RabbitMQ also support message priorities with the Stomp plugin?

The page http://www.rabbitmq.com/stomp.html says "All non-deprecated AMQP properties (...) , priority, (...) are supported".

Specifically, can a Stomp client access a queue which has the x-max-priority argument set as documented on https://www.rabbitmq.com/priority.html?

A user of my Stomp client library has defined the maximum priority of 9 and reported that an error is returned from the Stomp client:

precondition_failed PRECONDITION_FAILED - inequivalent arg 'x-max-priority' for queue 'hcp' in vhost '/': received none but current is the value '9' of type 'signedint'

I will try to reproduce the error in my environment, and wanted to let you know about this (unexpected) error message.

Am Sonntag, 22. Februar 2015 17:04:32 UTC+1 schrieb Michael Klishin:

[Michael Klishin]

I personally haven't tried it. But as long as the queue arguments and message properties are built correctly from STOMP headers, there should be no difference: the queues used by STOMP are not special.

It may be more convenient to use policies to define properties with sTOMP (that won't turn existing queues into priority ones).

MK

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[Gotthard, Petr]

Did the queue 'hcp' exist before the Stomp client set the x-max-priority argument? I suspect this may be the case. If a queue is defined without 'x-max-priority’, an attempt to redeclare this queue with 'x-max-priority’ causes PRECONDITION_FAILED.

 

Petr

[michael...@gmx.net]

Yes, the queue already existed before with x-max-priority set to 9. The Stomp client does not set the x-max-priority argument. I will try this.

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[Michael Klishin]

 On 5 June 2015 at 10:27:29, michael...@gmx.net (michael...@gmx.net) wrote:
> Yes, the queue already existed before with x-max-priority
> set to 9.

Then it uses the regular message store, which is unaware of priorities.

[michael...@gmx.net]

Hi,

the RabbitMQ 3.5.0 Stomp plugin seems to ignore a x-max-priority header. I have not checked this in the RabbitMQ source code yet.

My Stomp test code does not try to send messages, it only opens a STOMP 1.2 connection and sends a SUBSCRBE frame:

client sends:

SUBSCRIBE
destination:/queue/priority_queue
ack:auto
id:{E3CA1BDD-ACC2-45A6-B10C-3AC4C1E129F5}
x-max-priority:9


client receives:

ERROR
message:precondition_failed
content-type:text/plain
version:1.0,1.1,1.2
content-length:160

precondition_failed PRECONDITION_FAILED - inequivalent arg 'x-max-priority' for

queue 'priority_queue' in vhost '/': received none but current is the value '9'
of type 'signedint'

It seems the broker does not read the x-max-priority Stomp header into the queue arguments, or maybe some other condition is not fulfilled. (I have not checked the RabbitMQ source code for the Stomp plugin).

[Michael Klishin]

On 5 June 2015 at 11:09:49, michael...@gmx.net (michael...@gmx.net) wrote:
> It seems the broker does not read the x-max-priority Stomp header
> into the queue arguments

Seems so.

Filed an issue:
https://github.com/rabbitmq/rabbitmq-stomp/issues/13