[rabbitmq-discuss] Improved queue status

Matthias Radestock matthias at lshift.net
Sat Oct 4 00:03:19 BST 2008


Chris Van Pelt wrote:
> if I do a passive declare on a queue my message 
> count is 0 even though I may have 1000 items waiting in the TCP buffer 
> of my consumer.  This becomes a big issue if my items are taking more 
> than 5 seconds to complete.  The reason I want this information is so 
> that I can intelligently add more consumers as load fluctuates.

By the time there are 1000 items in the TCP buffer of the existing 
consumer isn't it too late to add more consumers?

> The simplest way to solve this issue in my mind would be for rabbitmq to 
> be able to return the number of un-acked items in a given queue.  Has 
> there been any discussion of this?

With basic.qos (which has been on our todo list for a while - sorry, 
some other items have higher priority) one can limit the number of 
unacknowledged messages per channel. Down to one if you wanted to, i.e. 
a client would have to ack a message before the server sends it another one.

That provides a fine degree of control over the maximum number of 
messages to keep in flight, and allows messages to stay queued up where 
they belong - at the server. It also makes the message count returned by 
queue.declare a reasonable parameter to guide consumer creation in the 
way you envisage.

> Also, rabbitmq kicks ass!!

Thanks. Glad you like it. Keep the questions coming.



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