At certain times during the week while I'm testing my Mobile Services app I get a 503 error (Service Unavailable). It happens whether I try to call the app from localhost or live on my Azure Website. It hangs around for 10-15 minutes and then goes away on its own. It doesn't seem to be caused by anything in particular that I am doing (i.e. I have not updated any code). The 503 error occurs when I'm trying to call one of my custom APIs in my Mobile Services account. A few of the requests make it through (strangely enough) but the majority return a 503 error.
I've seen that someone had a very similar problem here (Why does Azure give me an intermittent Error 503. The service is unavailable?) without an acceptable resolution.
I am using the free version of Mobile Services but I should be no where near pushing the limits of what the free version can handle; I am the sole user of the app right now.
It will soon be time to make the service live and I'm shuddering at the thought of support calls that will come in during one of these funky states the service gets into. Any help in debugging the problem would be greatly appreciated.
EDIT:
I've narrowed this down to a database problem. I have one main query (sproc) that I use to feed data to the UI. I noticed that when I get the 503 errors the query takes about 13 seconds (when run in SSMS). When things are running "normally", the query takes less than a second.
This doesn't solve my problem though, in fact it makes it more perplexing because I am using the Business Edition of Windows Azure SQL Database and there shouldn't be a 13 second fluctuation in execution time!
This problem seems to happen randomly. Is there some kind of caching in SQL Server that could explain this? Maybe my query really does take 13 seconds to execute and the caching superficially speeds it up.
Could you try transitioning your database/server to one of the "editions"? They have resource governance to promote predictable performance. Web/Business suffer from a noisy neighbor problem. It sounds like that may be your issue, considering it is intermittent.
Here's a link to a page describing the editions. https://msdn.microsoft.com/en-us/library/azure/dn741340.aspx
Related
We have a long running ASP.NET WebApp in Azure which has no real endpoints exposed – it serves a single functional purpose primarily reading and manipulating database data, effectively a batched, scheduled task, triggered by a timer every 30 seconds.
The app runs fine most of the time but we are seeing occasional issues where the CPU load for the app goes close to the maximum for the AppServicePlan, instantaneously rather than gradually, and stops executing any more timer triggers and we cannot find anything explicitly in the executing code to account for it (no signs of deadlocks etc. and all code paths have try/catch so there should be no unhandled exceptions). More often than not we see errors getting a connection to a database but it’s not clear if those are cause or symptoms.
Note, this is the only resource within the AppService Plan. The Azure SQL database is in the same region and whilst utilised by other apps is very lightly used by them and they also exhibit none of the issues seen by the problem app.
It feels like this is infrastructure related but we have been unable to find anything to explain what is happening so if anyone has any suggestions for where we should be looking they would be gratefully received. We have enabled basic Application Insights (not SDK) but other than seeing CPU load spike prior to loss of app response there is little information of interest given our limited knowledge of how to best utilise Insights.
According to your description, I thought of two points to troubleshoot your problem. First of all, you can track the running status of your program through the code, and put a log at the beginning and end of your batch scheduled tasks to record the status of each run. If possible, record request and response information and start and end information. This can completely record the time and running status of your task.
Secondly, you can record logs before the program starts database operations, and whether the database connection is successful. The best case is to be able to record, what business will trigger CPU load when operating, and track the specific operating conditions, in order to specifically analyze what causes the database connection failure.
Because you cannot reproduce your problem, you can only guess the cause of the problem. If you still can't find where the problem is through the above two points, then modify your timer appropriately, and let the program trigger once every 5 minutes instead of 30s.
Not sure if i should post here or on Serverfault but this morning we have been getting random 503 errors from Azure (web apps).
They occur from random places across the world and i do get them myself from time to time.
In our "Support Observe" view i do see a lot of errors:
I do not see that amount of erros in our event logs thou. I do however see some errors that could be something like.
6136
w3wp
Role environment . FAILED TO INITIALIZE. hr: -2147024891
and from W3SVC-WP that are really cryptic like.
*1
5
50000780*
I've found some other posts about these kind of errors here and they seems to point towards issue with Azure sometimes and sometimes not.
I'm on the East US datacenter. Anyone else having issues or can help me figuring out what this is. The fact that is occuring randomly across the world really do point towards an Azure issue?
I could also add that i do not do any load balancing so it could not be that one of the instances is down and or something like that. I have restarted and redeployed the code and so on as well.
We use Azure and have problems with our Cloud Service last two days.
We get 503 error on site. It looks like one of web-roles reboots sometimes. But in dashboard all of them works fine.
Application Insight and Logs doesn't show any problems. CPU, Memory, Exception rate - all OK.
But I found one interesting moment. SQL queries average time grew to 5 seconds. But I checked it on database, it worked normal. This means that 5 seconds is not execution time but connection.
It looks too much for trace inside data center.
Does anyone have any ideas how I can find a solution of this problem?
When your app generates a lot of exceptions in short time IIS stops application pool and you get 503 error.
For more details google for "IIS Rapid Protection".
I have a number of small MVC apps deployed as Microsoft Windows Azure websites. This has been working for several months.
Yesterday I rolled out a new one, and the deployment was unremarkable, everything worked fine. But a couple of hours later, access to the site was unavailable. The symptoms were that when the browser tried to navigate to the URL for that site, it would try to load for several minutes and then just give up with a completely blank page.
I attempted to stop and restart the site, and it worked once, but the symptoms came back several minutes later. Then I tried to stop and restart, and it didn't work.
I deployed the identical app to three additional URLs. Again, immediately on deployment, they all work fine, however, they fail at some interval in the future. They seem to not all fail at once. Sometimes restarting the site will fix the problem, and sometimes not.
IMPORTANT: If I wait for some period of time, the site may start to work again on its own.
However, deploying four versions of the app so that our users can go to a backup one if the primary one is not working is not optimal.
Any words of wisdom as to how I might go about debugging this?
ADDITIONAL INFO NOV 25, 2013:
When sites are failing, the IIS logs show either 500 or 502 Internal Service Errors. Our own MVC code is never hit, not even app_start.
You can start by checking the logs and remote debugging
http://www.drdobbs.com/windows/azure-sdk-22-supports-visual-studio-2013/240163499
Are the apps working locally?
Might not be the same problem, but from time to time our Azure instances will get the blue question mark of death as a status.
The reason we found out was that Microsoft will do upgrades on instances from time to time. If you have just one instance in a cloud service/role, then from time to time they will do maintenance and during that time it will be dead.
I have confirmed this with their support.
The only way to get around this that I know of is to create two instances. Then Microsoft guarantees ~99% availability.
Of course I also confirmed with them that this means twice the cost. =/
If that's not the issue I would enable RDP and get onto the machine to see what the problem is. Microsoft has these tools to help debug problems: http://blogs.msdn.com/b/kwill/archive/2013/08/26/azuretools-the-diagnostic-utility-used-by-the-windows-azure-developer-support-team.aspx
First, you should always run multiple instances of your web role with more than 1 upgrade domain. This is configurable in the service definition (CSDEF). Without this, you don't get an SLA from Microsoft, so you can't really complain that the VMs go down.
Second, to figure out what might be going on with these boxes, you should have both logs (my preference is to roll my own with page blobs or table storage), AND you should always have RDP access to a pre-production environment (production as well if you're not too fussed about security). Once on the box, look through the event viewer for errors.
Third, when an outage occurs check out the azure service dashboard (http://www.windowsazure.com/en-us/support/service-dashboard/) for outages.
Lastly, contact Microsoft support. It may take a few hours, but they are pretty good.
That it is happening repeatedly and for extended periods of time (more than 5 minutes), I would be there's something wrong with your hosted service. Again, RDP in and poke around. Good luck.
To debug your sites try to enable diagnostic logs:
http://www.windowsazure.com/en-us/develop/net/common-tasks/diagnostics-logging-and-instrumentation/
Another nice way to look around your site is using the debug console:
https://github.com/projectkudu/kudu/wiki/Kudu-console
I'm getting occasional 503 errors on our site. It usually happens after not visiting the site for a while. The whole page might return 503 or just some resources like css or js files.
It seems to go away after you've surfed the site for a bit and hit all of our servers.
Elmah doesn't show any errors.
I've gone into the logs on each of our servers (three medium web roles on azure) and I can't find any problems.
Our deployment has been up since December without a code change, we've been having this problem for about a week.
One thing to note is that when this happens the site doesn't shut down. I would think that would happen if IIS was crashing and restarting (even with three servers).
Does anyone know how to diagnose or fix this problem?
While this could be code related, I'll assume you've already explored this route as much as possible via logs (and since you haven't deployed new code). Having said that:
Do your issues align with the Compute service degradation events shown in the Azure Dashboard over the past several days? Look at Historical View and you'll see a few issues around Compute. Depending on your data center, maybe this is related?