IIS 7.0 gives 503 error and stops the application pool
I had similar problem today when an application pool using Windows user identity X stopped working after password change for that user.
Apparently, some information linked to old credentials was stored in the system, and I solved the problem by:
- switching app pool identity to NetworkService
- switching it back to X using the new password
So far it's working fine.
I found an article saying
The fix is to ensure that the Service/AppPool accounts have the ‘Log on as a batch job’ and ‘Log on as a service’ user rights on the server. This right can be found in Local Security Policy > Computer Configuration > Windows Settings > Local Policies > User Rights Assignment. Either remove the conflicting Group Policy and fix the Local Policy or add the rights to the Group Policy.
While there may be several reasons why this may occur, in this specific case, the 503 error was occurring because the Application pool failed to start. This was because the password was changed recently for the Identity under which the application pool was trying to run. Fix was to go to the IIS Manager-> Application Pool -> Advanced Settings -> Process Model -> Identity and set the password to the new one.
It would also help to check the Event Viewer Logs(Event Viewer (Local) -> Windows Logs -> Application to look for specific causes of failure before proceeding to troubleshoot any further.