Azure Web App swap happening BEFORE warmup

Question

Since about a week when I publish a new version of our Web App and do a Swap from Staging to Production, it actually seems to swap before the warmup initialization is done.

As it is a large application it will takes more then five minutes to warmup the site, making the application unresponsive.

I have official Azure support, but it is taking a long time to respond to this request and I still have no answer that works.

I can't fix any issues on our platform or publish a new version without bringing the whole site down for eight minutes. This is a highly visited website, with paying clients.

Does anyone know:

• anything that I could investigate myself?
• a workaround or any tips that I can take a look at myself to try to fix or work around this issue?

Extra information

I do use applicationInitialization, and I see that Azure is hitting the pages - it just happens after the swap instead of before.

<system.webServer>
    <applicationInitialization>
        <add initializationPage="/nl" hostName="mydomain.com" />
        <add initializationPage="/warmup-application-for-azure" hostName="mydomain.com" /> (special page just for warming up services)
        <add initializationPage="/deeplink1" hostName="mydomain.com" />
        <add initializationPage="/deeplink2" hostName="mydomain.com" />
        [etc]
    </applicationInitialization>
</system.webServer>

Answer 1

Maybe not 100% relative to this question but since I had similar issue with warm up I want to share how I solved it.

I used to have issue with auto-scaling because my nodes were not warmed up due to url rewrite module. So what if you have url rewrites in your app make sure that you are checking for

 <add input="{WARMUP_REQUEST}" pattern="1" negate="true" />  

Now this is in official documentation and it has link to common problems