Hi - we are using Azure CDN to deliver adaptive streaming video and we are intermittently getting HTTP 504 Gateway Time-out errors which cause the video playback to stall and jump back into life at a different point in the video a few seconds later. This behaviour was first noticed around the beginning of April and not before and we're wondering if something has recently changed in the CDN setup? Looking at other threads on this board we can see that files less than 1MB in size are not cached at they are grabbed from source each time they are requested - and we fall into that category as the video stream fragments are generally 50K-400K in size. Bearing this is mind is there any advantage in us trying to use Azure CDN or should we just grab the files straight from blob storage?? We don't really want to do this as the idea of serving video content locally to user from a cache is appealing. Any thoughts / ideas much appreciated - thanks Ed
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Do you mean this thread? http://social.msdn.microsoft.com/Forums/en-US/windowsazuredata/thread/093da9d3-0fca-4a53-af5d-5305e15c311d :
If the file is smaller than 1 MB then parent caches will not help performance
As allen tag in that thread, the "parent level" mentioned by MSFT support is used to troubleshoot your specific case. It's not recommended for others to follow the "how best you can utilize the CDN service" you posted because it is subject to change.
I've tested CDN service with less than 1 MB file (image file) in the following sample in Training Course, and it works fine at my side, would you like to have a try with it?
hope this helps.
Hi guys - thanks for getting back to me.
Steve asked: Can you point to a source that says files less than 1MB in size aren't cached?
...and Arwind correctly linked to this post: http://social.msdn.microsoft.com/Forums/en-US/windowsazuredata/thread/093da9d3-0fca-4a53-af5d-5305e15c311d
From reading that message we think we fall into the category of a "non-cached file type for files less than 1MB in size" - as our streaming video fragment files are just binary data ranging from 50K-400K in size, do you agree? (We have actually used the ideas shared on Steve's blog (http://blog.smarx.com/posts/smooth-streaming-with-windows-azure-blobs-and-cdn) in order use the Azure blob storage as an adaptive streaming host.)
As an aside, last night we tried reconfiguring things at our end so that the files were delivered directly from blob storage and not via CDN and the results were that initial playback appeared to pick up slightly faster plus we experienced fewer playback glitches (although there were still some). What do you think are the pros and cons of bypassing CDN completely? (I am not only thinking from a technical perspective - does anyone have a handle on Azure costs?)
Finally, none of the above explains why we're seeing "gateway time-out" errors. Does anyone have any ideas about that??
More news from this end.
We have been running some side-by-side tests with the same video content being streamed via CDN vs. direct from blob storage. Interestingly here in the UK during the morning things are good on both, but as the day progresses the CDN delivery degrades. We are seeing videos taking 5-7 seconds to start playing via CDN compared to 2-3 seconds direct from blob storage, plus we are getting video freezes and jumps via CDN which we are not seeing from blob storage.
Here are a couple of URLs where you can see this happening for yourself (you'll need at least Silverlight 4 installed to view these)...
Video playback via CDN = http://bubbleservices.cloudapp.net//Richpartnership_Licensee_Group/Video_playback_test_via_CDN
Video playback direct from blob storage = http://bubbleservices.cloudapp.net/Richpartnership_Licensee_Group/Video_playback_test_direct_from_blob_storage
As a result we are wondering if the US coming online partway through the UK business day is affecting things and why this would be?
Any thoughts on this or my previous post above??
We found that our problems disappeared as quickly as they had appeared, without any changes from us. We guess that the people that operate the CDN are making config tweaks from time-to-time and what we saw was the result of one of these which was then subsequently rectified.
Sorry that I can't help with your issue - but if I learn anything more I will post back here.
Thanks for the reply.
In my end i can see the problem come and go as well. there are time that the cdn works perfectly ( as i write this message it does), but some other time ( like when i write this previous post) it doesnt.
If i access the cdn url i get 2 times ok response 5 times an error ( 504). if that's happens then i think that the cdn is not much good platform to disturbed files.
I'll keep trying to find out a solution as well.