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On 11/07/2006, at 1:12 AM, Steve Richter wrote:
I have found two way data queues very difficult to code. You have to assign a transaction id to differentiate responses to other clients from your client. The response queue has to be keyed by transaction id. What happens when the server is down or stuck? Your client then waits for how long for the return code? Did you say 10 seconds? Well what if the system is running slow or another client has sent a large transaction to the server?
What you describe here forces a synchronous process on to queues. There is no reason to wait for a return code. Deal with it when it arrives.
Also is no requirement for keyed queues. Each sender could have it's own response queue.
When do you clear the return queue of unreceived response messages?
Why would they not be received unless the sender died? Given that the sender is likely (and especially given your description) to be an interactive job it won't die without someone noticing.
Clearing can be handled during sender start, during a nightly clean up, or by deleting an recreating the queues.
When the return message is more than 1 day old or the sending job is no longer in the system? Then you have to permanently store the transaction in in a file so you cancalc the job and age of the transaction.
Not true. You can use the QMHRDQM to check the enqueue date and time. This can be used to determine the age and old entries can be removed.
With a program call none of these issues have to be addressed.
True, but what you're objecting to is the asynchronous nature of queues. If you want synchrony then use a synchronous process but don't use your requirement for synchrony to damn all legitimate uses of queues.
None of your objections are show-stoppers. They can all be handled by a decent design. All of your objections simply indicate that MAYBE queues are not a good fit for your requirements. Just because they don't (or can't be made) to work for you doesn't negate them as an ideal solution for someone else.
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