Activation

TimChapman


I was testing around with a sample service broker app using activation, and came across an interesting question. The little app sends a series of four messages to a queue, either on the same conversation or on seperate ones. Each message invokes one stored procedure in my activation procedure. All the procedure does is enter a record into a test table and then wait for an allotted amount of time. In my example, the first message called a proc that waited 20 sec, the 2nd one that waited 10 seconds, the third 5 seconds, and the 4th 1 second. I am using internal activation on the queue. It seemed that in both scenarios (sending on 4 separate conversations and on one conversation) the procedures executed "almost" sequentially. "Almost" meaning that the first procedure was done before the last one started executing. It makes sense to me that this would happen where I sent them on the same conversation, but not really when I sent them on 4 seperate ones. Is it because when I call a procedure from my activation procedure it locks the queue so that another message cannot be processed (I'm processing a message at a time) How could I make it so that the 4th procedure (the one that only waits 1 second) returns before the 1st procedure (the one that waits 20 seconds)

Remus Rusanu


MAX_QUEUE_READERS =

TimDBA

Sorry, my max_queue_readers where 5 in both situations.

Tim

Remus Rusanu

With one message per conversation then new instances of the stored procedure may be launched, so a message that arrived later may be processed sooner by a new instance activated procedure.

Also, even locally, the message order is only guaranteed within a conversation, so 5 messages sent on 5 conversation may arrive on the target queue in any order (unlikely to arive in different order, but one should not assume order between conversations)

TimDBA

You reference that new instances of a sproc may be launched for one message per convo, but what determines if it will or not Will it only happen if some threshold is exceeded on the queue The reason I was doing the little test was because I haven't seen any articles out there really detailing good ways to run large processing queries asynchronously for one application, so I was wanting to write one. My main curiosity was if there was any way to modify any of the settings for the procedure activation (which I don't think that there is).

TimDBA

I just read your blog entry on Parallel Activation...neat stuff. Although, I doubt that it is something I would ever need to implement. I changed my procedures a bit so that they delay for a longer time period, and it appears that a new activation occurs ~ 5 seconds.