Swap with preview timeout

Question

Getting a "polling timout" with completing the swap. Both instances are running and warmed up during the swap.
I can't figure out an effective way to debug this. This process worked perfectly about two weeks ago, but have suddenly stopped working.

Have followed numerous tutorials talking about applicationInitialization, WEBSITE_SWAP_***, rewrite-rules to prevents https-redirection and so on.

It's weird that we can't access an official and definitive guide on how to properly set it up - I suppose its a very common requirement in most production instances.

Can you guys point me to an updated wiki, blog or something that goes into details on how to debug the process?

Answer 1

Thanks for getting back to me.

The official documentation here:
https://learn.microsoft.com/en-us/azure/app-service/deploy-staging-slots
https://learn.microsoft.com/en-us/azure/app-service/deploy-staging-slots#troubleshoot-swaps
And the "unofficiel" one you have linked to from the documentation as well:
https://ruslany.net/2017/11/most-common-deployment-slot-swap-failures-and-how-to-fix-them/

When everything was working I had the following setup

Step 1
Prevent HTTPS-redirection in web.config via (and other rewrite-rules)
<add input="{WARMUP_REQUEST}" pattern="1" negate="true" />
<add input="{REMOTE_ADDR}" pattern="^100?." negate="true" />

Step 2
Whitelist internal IP's from "Access Restrictions" via the portal
100. 0.0.0/8
10. 0.0.0/8
127. 0.0.1/32

Step 3
WEBSITE_SWAP_WARMUP_PING_PATH = /warmup
WEBSITE_SWAP_WARMUP_PING_STATUSES = 200
WEBSITE_WARMUP_PATH = /warmup

The warmup-endpoint does nothing currently, except being very fast to deliver a response.

I then "swap with preview" so I can invoke a longer warmup-cycle that takes around 10-20 minutes.

Have tried replacing step 3 with the "<applicationInitialization>"-method in the web.config. Doesn't solve the issue though.