http 503 service unavailable on SharePoint

Error: http 503 service unavailable

Whenever I see this error message on share point site, first I look at status of Application pool . If it is disabled/stopped then I look at windows event-viewer log .

There were couple of warning messages followed by an error message in event viewer .

Warning Message 1: Event ID 5059 : Event Source : WAS

“The identity of application pool SharePoint – mysharepoint.loacl443 is invalid. The user name or password that is specified for the identity may be incorrect, or the user may not have batch logon rights. If the identity is not corrected, the application pool will be disabled when the application pool receives its first request. If batch logon rights are causing the problem, the identity in the IIS configuration store must be changed after rights have been granted before Windows Process Activation Service (WAS) can retry the logon. If the identity remains invalid after the first request for the application pool is processed, the application pool will be disabled. The data field contains the error number.”

Warning Message 2: Even ID 5057 : Event Source: WAS
“Application pool SharePoint – mysharepoint.loacl443 has been disabled. Windows Process Activation Service (WAS) did not create a worker process to serve the application pool because the application pool identity is invalid.”

Error Message :
“Application pool SharePoint – mysharepoint.loacl443 has been disabled. Windows Process Activation Service (WAS) encountered a failure when it started a worker process to serve the application pool.”

As a solution ,

I have changed application identity account password and set the same password for that service account from share point management shell .

Set-SPManagedAccount -identity MYDOMAIN\serviceaccount_user -NewPassword (Converto-Securestring “P@ssword” -AsPlainText -Force) -SetNewPassword

Then restarted WAS service from command prompt window ( run as Administrator )
net stop was /y
net start was
net start w3svc