"HTTP Error 503. The service is unavailable." in sharepoint 2010

Today, i got a very weird issue in my sharepoint development server,

all SharePoint site including the central Administrative Portal suddenly did not work after i restart my IIS.

Here is the Errorr Message shown in the browser

"Error: Service Unavailable HTTP Error 503. The service is unavailable."

First  I check the applicaiton log there is no error found.
Second I went to the SharePoint  log file folder and check the SharePoint log. No Error had been Logged there.

Finally I found the following error in the IIS Log

"Application pool SharePoint Central Administration v4 has been disabled. Windows Process Activation Service (WAS) encountered a failure when it started a worker process to serve the application pool."

then i know that Central Administrative Portal failed due to the application pool stopped functioning.

I try to restart the app pool, but it failed again after i launch the central administrative portal. i thought the app pool might corrupt, then i used another app pool, but it failed immediately. when I try to create a new app pool to determine the issue, i found out that the service account had been expired, the root cause is that i forgot to set password of this service account never expired.


the solution is i reset the password of service account and check to make sure this password never expired. Then all the SharePoint site is back to normal and Central Administrative portal is functioning again.