#Slot swap - 503 errors after changing app service plan

1 messages · Page 1 of 1 (latest)

gloomy karma
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Last week I changed the app service plan from Premium v2 P2V2 to Premium v3 P1V3 and now I get a short 15 - 20 seconds of error 503 after performing a swap with preview.

  1. Click Perform swap with preview
  2. Wait for staging slot to warm up, test, everything is working ...new version is running etc...
  3. Click complete swap...wait 15-20 seconds, service times out, 15 seconds later service is back

This did not happen with the Premium v2 P2V2 app plan and only started after I switched plans.

I already have WEBSITE_ADD_SITENAME_BINDINGS_IN_APPHOST_CONFIG = 1. This helped with issues in the past.

All environment variables have Deployment slot setting = true

I am using ApplicationInsights and recently switched to connection string from Instrumentation Key

Configuration:
Stack: .NET
.Net version: .NET 6 (LTS)
Instance Count: 1

We use to use lower tier hosting and then scale out when needed but found the sometimes adding a new instance had the same 503 error and we settled with just running a higher tier plan with a single instance.

#

Health Check is enabled

graceful flame
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sounds like the instance is restarted after the swap. perhaps an app setting changes?

gloomy karma
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I created a 3rd slot so I can test swapping between 2 staging slots now. I was able to replicate the issue swapping between them. I will try removing app settings that differ in the hopes of finding the problem without affecting the production slot.