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I have two servers running an API, but on one of them the API is not responding anymore. This happened right after my colleague added another API under the same application pool... Since then the API stopped responding and I get a 503 Service Unavailable error, but only on the one server. The other server runs the API without problems.

This is what I tried:

  • I first removed the API my colleague added from application pool and restarted the pool, which didn't work
  • Recycling the application pool.
  • Rebooting the server.
  • Changing the Rapid-Fail Protection setting to false.
  • Changing the identity from ApplicationPoolIdentity (which it has always used) to LocalService, LocalSystem, NetworkService and back to ApplicationPoolIdentity.
  • Creating a new application pool and moving the API to that one. Stop/start/recycle not working here either.

The application pool keeps running when I start it and I see no errors in the event viewer. The code on both servers are the same. I tried connecting to the server with telnet and that worked, so there are no network issues. I can still access the API throught localhost, but when connecting through the website I get the 503 error.

Is there anything else I can try?

Isoldhe
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1 Answers1

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According to your description, it could be that the user identity is outdated. Especially, the application pool will stop when the next request arrives. Try to assign a new user/password to the application pool identity.
In addition, there are some other reasons that lead to this issue, check this discussion for more details.
HTTP Error 503, the service is unavailable
https://bobcares.com/blog/iis-http-error-503-the-service-is-unavailable/

Abraham Qian
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