Why would azure be restarting website when I do a deployment slot swap?

Question

I've a .net 4.5 website running on Azure Websites. I've a staging deployment set up. I warm up both sites and then I run the swap process (both from azure portal and from Azure powershell). No matter what I try, the swapping process would restarts both my websites and they take about 3 minutes to boot up.

I was under the impression the deployment swapping was supposed to keep the websites "warm" and have no down time? My websites are unusable for about 3 minutes!

As far as I can tell both production and staging slots have the same application settings etc.

Any advice or pointers would be greatly appreciated.

Answer 1

I know this is an old question but I thought I'd answer if someone stumbles across it. I've discovered that if you have slot-specific configuration settings (even if they have the same value), Azure needs to restart the app domain during the swap in order to apply the new settings.

Assuming a 'staging' and a 'production' slot, the behaviour is roughly as follows (not necessarily in this order):

• Swap is initiated
• Config for 'production' is applied to the 'staging' site - app domain is restarted
• Config for 'staging' is applied to the 'production' site - app domain is restarted
• DNS/IP settings are updated, swap is completed
• Users get annoyed that the site is now 'down' temporarily

If you use the new 'swap with preview' option, it will still restart the app domain, but it will pause before it actually applies the swap, allowing you time to warm up the 'staging' instance after it has restarted.

Answer 2

If you configured AutoSwap for your website, I believe there should be no downtime for the website - this site describes the steps needed (lots of i's to dot and t's to cross) https://azure.microsoft.com/en-us/documentation/articles/web-sites-staged-publishing/