I am evaluating the Windows Azure WebSites Preview (WAWS I think, not sure with all these changing names and acronyms that Microsoft loves to mutate on) with DotNetNuke (DNN) which I am also using for years on a "non cloud" V-Server. Installation was a breeze. I only tried the free shared instance and I have tested with 1 and with 3 active instances with similar results.
First hit performance always was a problem with my previous DNN installations, when a website was idle for a while (15 minutes or so) the process would stop and then the next unlucky visitor will wait at least around 20 seconds. With some IIS tweaking it was possible to minimize this problem but I had the best results with a monitoring service that will request a page from DNN every five minutes and keep the process up.
While surfing the DNN page usually performs well on WAWS, I immediately noticed that the "first hit" problem is an issue with DNN on WAWS so I configured a monitoring service for the page. That did not help and the monitoring service will always report that the site is down. Almost as if WAWS was trying to avoid keeping the site up since it detected that only a monitoring service was requesting the page.
Also, when navigating on the DNN pages and then pausing for just a minute or two, I will often get an "Internet Explorer could not load this page" error with no specific error code.
Do others have experience with the DNN performance on WAWS or maybe know why the "first hit" is such a problem?
I suspect that Microsoft is actively trying to avoid the keep-alive tricks that many ASP.Net devs use. WAWS, like many shared hosting platforms, relies on only having a certain number of active websites on the server at any one time in order to achieve higher server densities and keep the cost of hosting under control. This is one of the reasons that they can offer this service for free.
I think what you want to look into is "keep alive."
What you are experiencing is the ASP .NET process getting killed for your application due to inactivity. When the process isn't in memory and the site is accessed IIS has to spin it back up which is the 10 - 20 second lag you get upon accessing your site as the process gets up again and/or just in time compiles.
You can schedule some 3rd party monitoring services to check your site every 10 minutes via an HTTP request that will keep your site up. Just pinging it will not keep it up.
Related
By looking at my Pingdom reports I have noted that my WebSite instance is getting recycled. Basically Pingdom is used to keep my site warm. When I look deeper into the Azure Logs ie /LogFiles/kudu/trace I notice a number of small xml files with "shutdown" or "startup" suffixes ie:
2015-07-29T20-05-05_abc123_002_Shutdown_0s.xml
While I suspect this might be to do with MS patching VMs, I am not sure. My application is not showing any raised exceptions, hence my suspicions that it is happening at the OS level. Is there a way to find out why my Instance is being shutdown?
I also admit I am using a one S2 instance scalable to three dependent on CPU usage. We may have to review this to use a 2-3 setup. Obviously this doubles the costs.
EDIT
I have looked at my Operation Logs and all I see is "UpdateWebsite" with status of "succeeded", however nothing for the times I saw the above files for. So it seems that the "instance" is being shutdown, but the event is not appearing in the "Operation Log". Why would this be? Had about 5 yesterday, yet the last "Operation Log" entry was 29/7.
An example of one of yesterday's shutdown xml file:
2015-08-05T13-26-18_abc123_002_Shutdown_1s.xml
You should see entries regarding backend maintenance in operation logs like this:
As for keeping your site alive, standard plans allows you to use the "Always On" feature which pretty much do what pingdom is doing to keep your website warm. Just enable it by using the configure tab of portal.
Configure web apps in Azure App Service
https://azure.microsoft.com/en-us/documentation/articles/web-sites-configure/
Every site on Azure runs 2 applications. 1 is yours and the other is the scm endpoint (a.k.a Kudu) these "shutdown" traces are for the kudu app, not for your site.
If you want similar traces for your site, you'll have to implement them yourself just like kudu does. If you don't have Always On enabled, Kudu get's shutdown after an hour of inactivity (as far as I remember).
Aside from that, like you mentioned Azure will shutdown your app during machine upgrade, though I don't think these shutdowns result in operational log events.
Are you seeing any side-effects? is this causing downtime?
When upgrades to the service are going on, your site might get moved to a different machine. We bring the site up on a new machine before shutting it down on the old one and letting connections drain, however this should not result in any perceivable downtime.
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 have a Website hosted on Windows Azure. This website is a custom ASP.NET MVC 4 site hosted as a shared web site instance. Within the past couple of days, I've started to get large spikes in CPU Time. These spikes have been sustained and have caused my web site to get suspended. However, I'm not sure how to determine the cause of these spikes. Here is what I've done so far:
I attempted to look at the diagnostics via the Windows Azure FTP drop. I did not see anything there.
I reviewed my Google Analytics to see if there was anything out of the ordinary. The site had 20 visitors yesterday. So nothing crazy.
How can I identify the culprit of the the CPU spike? Once it spikes, it just sits there for hours. I'm not sure what would cause this.
Thank you
Have you tried running your site on your local box and simulating your visitor traffic, exercising all your website's features?
Testing locally is 1000's of times easier and more revealing than trying to debug a site that's running live.
If you still can't find anything wrong when running locally, consider using logging and tracing to strategic points in your site so that you can see how often, and how long it takes for your site to execute complex operations.
This question already has answers here:
Closed 10 years ago.
Possible Duplicate:
App pool timeout for azure web sites
I am working on an asp.net mvc 4 app that is hosted in Windows Azure. This app will not have a lot of traffic as people will intermittently (once an hour) use it. I wanted to try using Windows Azure.
My app is currently set to use the FREE web site mode. I noticed that after 30 minutes, the site takes a long-time (> 5 seconds) to load. After that initial load, its fast. Then, if someone doesn't use it for another 30 minutes, it takes >5 seconds to load again.
I then tried upping the web site mode to a SHARED instance. I experienced the same problem there.
I then tried upping the web site mode to a RESERVED instance. The problem then goes away.
While I'd like to use Windows Azure, paying $50+ a month for a RESERVED instance is pretty expensive for a site that few have used up to this point. However, I can't have the initial lag. That will just defer the few users I have. You could say you get what you pay for. At the same time, I have a hard time believing others are experiencing this problem and not complaining. There has to be something I'm missing.
I figure the problem has to deal with the application pool resetting. However, I can't seem to figure a way around this. Is anyone familiar with this issue? Is there a way to fix it on a FREE or SHARED instance?
Thank you!
This is expected behavior based on how Windows Azure Web Sites work. The app pool they live in is spun up "on demand" and then hangs around for a time period.
For a detailed (and shameless plug) you can check out my article on this: http://www.simple-talk.com/dotnet/.net-framework/windows-azure-websites-%e2%80%93-a-new-hosting-model-for-windows-azure/
In summary:
Web Sites are hosted in a process on a farm of machines running IIS. If a site is idle for some time then the process is torn down automatically. Also, if the box is seeing a lot of pressure due to the other sites on the box the idle timeout may come down quite a bit (even as low as five minutes). When the next call comes in you'll see the process spun up again (likely on a completely different server). This is because you are in a shared environment (and is similar to how Heroku works). Once you move to reserved then you are the ONLY person on that virtual machine and if you suffer from noisy neighbor issues in processing its' because of your own stuff.
There are ways to keep your site "up", such as having a job that pings the url frequently; however, given that the idle timeout is somewhat fluid it may not solve every case. You can check out a recent post by Sandrino on how to use Azure Mobile Services as a job scheduler: http://fabriccontroller.net/blog/posts/job-scheduling-in-windows-azure/ . There are also 3rd party services available that can do the ping for you automatically.
To be honest, the web sites are a great feature for quick development and test, or even relatively low traffic sites as you are talking about. If you need a high level of uptime and better performance then you'll want to look at Reserved, or another option if the cost isn't in line with expectations.
This isn't an Azure problem. It is a "feature" of any web site hosted in IIS. The default time-out for app pools is 20 minutes. Read about App Pool timeouts here - http://technet.microsoft.com/en-us/library/cc771956(v=ws.10).aspx - one method is to create a keep alive page and ping the page every 10 minutes or so.
I have a web application that's consuming a WCF service. Both are slow on warmup after IIS reset or app pool recycle. So, as a possiible solution I installed Application Warm-Up for IIS 7.5 and set it up for both web site and wcf service.
My concern is, it doesn't seem to make any difference - first time I hit the site it still takes long time to bring it up. I checked event logs, there are no errors. So I'm wondering if anything special needs to be done for that module to work.
In IIS manager, when you go into the site, then into Application Warm-Up, the right-hand side has an "Actions" pane. I think you need the following two things:
Click Add Request and add at least one URL, e.g. /YourService.svc
Click Settings, and check "Start Application Pool 'your pool' when service started"
Do you have both of these? If you don't have the second setting checked, then I think the warmup won't happen until a user hits the site (which probably defeats the purpose of the warmup module in your case).
There is a new module from Microsoft that is part of IIS 8.0 that supercedes the previous warm-up module. This Application Initialization Module for IIS 7.5 is available a separate download.
The module will create a warm-up phase where you can specify a number of requests that must complete before the server starts accepting requests. Most importantly it will provide overlapping processes so that the user will not be served by the newly started process before it is ready.
I have answered a similar question with more details at How to warm up an ASP.NET MVC application on IIS 7.5?.
After you have fixed possible software/code optimizations allow me to suggest that each and evey code needs processing via hardware cpu. And our server skyrocketed in performance when we went to a multicore cpu and installed more GIGS of ram and connected UTP-6 cable insetad of standard UTP 5e cable onto the server... That doesnt fix your problem but if you are obsessed with speed as much as us, then you will be interested in the various dimensions that bottleneck speed.