While this question is particular to Azure, I'm sure that it is a common situation for cloud computing in general.
I have a list of tasks that I need run at a certain time. With a window's server, I can use Task Scheduler and schedule my program to run at a certain time. I could go a step further and create a windows service that would run at a given interval and then execute the appropriate task.
Does anyone have a suggestion on the best approach is for a cloud computing environment?
I could create a worker role that polls the task list every second and then throws the appropriate task into a queue that is processed by another worker role.
I could create a worker role that would run once a day, grab all the tasks and submit them to a queue. The processor roles would then pull an item off the queue and process at the appropriate time.
Any other suggestions?
Best Answer
You can set up a Service Bus Queue and use that as the scheduler.
Send messages into the queue by setting ScheduledEnqueueTimeUtc on the message to the desired time and the message will show up in the queue at that time. In the executing worker/web role you set up a receiver on that queue and that will then get the job as soon as the message shows up, i.e. the job is due.
The nice thing about that is that you can use this to balances jobs across multiple instances and since the timer is completely external to your app you don't have to store and resurrect and manage it. SB does all that for you.
One caveat: SB doesn't have facility to cancel scheduled messages.