Set visibilitytimeout to 7days means automatically delete for azure queue?

Question

It seems that new azure SDK extends the visibilitytimeout to <= 7 days. I know by default, when I add a message to an azure queue, the live time is 7days. When I get message out, and set the visibilitytimeout to 7days. Does that mean I don't need to delete this message if I don't care about message reliable? the message will disappear later 7 days.

I want to take this way because DeleteMessage is very slow. If I don't delete message, doesn't it have any impact on performance of GetMessage?

Answer 1

Based on the documentation for Get Messages, I believe it is certainly possible to set the VisibilityTimeout period to 7 days so that messages are fetched only once. However I see some issues with this approach instead of just deleting the message once the process is done:

• What happens when you get the message and start processing it and somehow the process fails? If you set the visibility timeout to be 7 days, then the message would never appear in the queue again and thus the process it was supposed to do never gets done.
• Even though the message is hidden, it is still there in the queue thus you keep on incurring storage charges for that message. Even though the cost is trivial but why keep the message when you don't really need it.
• A lot of systems rely on Approximate Messages Count property of a queue to check on the health of processes which are performed by messages in a queue. Please note that even though you make the message hidden, it is still there in the queue and thus will be included in total messages count in the queue. So if you're building a system which relies on this for health check, you will always find your system to be unhealthy because you're never deleting the messages.

I'm curious to know why you find deleting messages to be very slow. In my experience this is quite fast. How are you monitoring message deletion?

Answer 2

Rather than hacking around the problem I think you should drill into understanding why the deletes are slow. Have you enabled logs and looked at the e2elatency and serverlatency numbers across all your queue operations. Ideally you shouldn't be seeing a large difference between the two for all your queue operations. If you do see a large difference then it implies something is happening on the client that you should investigate further.

For more information on logging take a look at the following articles: http://blogs.msdn.com/b/windowsazurestorage/archive/tags/analytics+2d00+logging+_2600_amp_3b00_+metrics/ http://msdn.microsoft.com/en-us/library/azure/hh343262.aspx

Information on client side logging can also be found in this post: e client side logging – which you can learn more about in this blog post. http://blogs.msdn.com/b/windowsazurestorage/archive/2013/09/07/announcing-storage-client-library-2-1-rtm.aspx

Please let me know what you find.

Jason