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From Gordon Sim <g...@redhat.com>
Subject Re: Evaluation of requirements
Date Wed, 29 Aug 2012 10:55:29 GMT
On 08/29/2012 10:52 AM, Caesar Holger (KGQI 1) wrote:
> Hi Gordon,
>>> 4) There is no feature to detect slow/hung consumers
>> You can get an alert when the backlog of messages for a subscriber
>> reaches a configured level. That would be indicative of a slow
> consumer.
> How can I do that? Setting something like
> "default-event-threshold-ratio" or "alert_size"? Can we be sure that it
> is one single consumer that is too slow on reading and not just the
> ensemble of all consumers?

Yes, you can set the point at which an alert is generated on a per queue 
basis, and each topic subscriber will have their own queue using 
qpid.alert_size and/or qpid.alert_count when creating the queue (or 
x-qpid-maximum-message-size, x-qpid-maximum-message-count which are 
aliases for the same options).

(If you have a queue shared between multiple consumers then the fact 
that one of them is slow is less relevant; the backing up of the queue 
can of course still be detected in the same manner).

The alert message will contain the queue name and the depth (message 
count & aggregate size). That is usually reasonably simple to tie back 
to a particular topic subscription.

>>> 8) SQL92-compliant message selectors as defined in the JMS standard
> are not
>>> supported
>> They are not yet supported by the c++ broker, but the JMS client can
>> evaluate them on the client side. So logically the feature is there,
>> though less efficiently implemented than if they were evaluated server
> side.
> I tried using a message selector in the client using an SQL92 compatible
> string from the Oracle JMS API ("NewsType = 'Sports' OR NewsType =
> 'Opinion'"). However I get the following exception:
> "javax.jms.InvalidSelectorException: cannot create consumer because of
> selector issue"
> Do you have any idea why this is?

No, I don't see why that should be invalid. Its not a particularly 
helpful error message either... Was there a linked exception tied to 
that with any more detail.

Anyone on the JMS side able to suggest anything here?

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