Azure Service Bus Queue ScheduledEnqueueTimeUtc Delayed

Question

I am encountering an odd problem. I have a cloud service A that puts messages into a service bus queue for another cloud service B to read. Cloud service B can take about a second to process what it needs to do, then it puts a message back into a queue for cloud service A. When cloud service B does this it uses the ScheduledEnqueueTimeUtc to put a delay of around 1 - 10 seconds on the message.

Last Friday the azure outage brought this application down completely. When I brought it back online, ScheduledEnqueueTimeUtc is always causing a delay of at least 10 seconds. For instance, I generate a datetime that is between 1 and 10 seconds in the future. I set that as the ScheduledEnqueueTimeUtc and I also put that time as a property on the message I am sending, I compare that datetime property to the EnqueuedTimeUtc property of the message when I receive it back in cloud service A. These 2 times should be pretty close together, and that is the way it has been working for months up until last Friday.

So now cloud service B is saying it put this message into the queue in 1 second. Cloud Service A says it didn't get into the queue for 12-14 seconds. I am using async methods when putting messages into queues. There is no delay if I do not use ScheduledEnqueueTimeUtc, the times match up close enough when I look at them back in cloud service A. But if I set ScheduledEnqueueTimeUtc even 1 second in the future it seems to not show up in the queue for 12-14 seconds.

I am working around this now by using quartz.net to schedule messages instead of setting the ScheduledEnqueueTimeUtc property. But it just seems really odd that this started happening.

Answer 1

From ScheduledEnqueueTimeUtc Property's documentation:

"Message enquing time does not mean that the message will be sent at the same time. It will get enqueued, but the actual sending time depends on the queue's workload and its state."

That property causes the message not to be delivered immediatelly. It won't be delivered before the set time, but there is not assurance that it will be delivered exactly at that time.

If you need high resolution scheduling, Quartz may be an option. You might also evaluate the new job scheduler that is part of the Mobile Services preview.