503 "service unavailable"

[Tanmaya]

Troubleshooting 503 "service unavailable"

This error is generated by World Wide Web Publishing Service, which serves incoming http requests by creating IIS worker processes. When it fails to build a worker process, it will generate 503 service unavailable error.



There are many reasons including invalid application pool setting, fail to build the process because of incorrect application pool identity configurations, wrong IIS setting that may lead the worker process to fail to start.

In such case you’ll need to check following things,

1) Make sure that whether the application pool is running or is stopped
2) Look in to event logs, for events like the “IIS worker process could not initialize because it failed to load a module DLL”.

There are several reasons for worker process failure,
The configuration is invalid.
Mismatch in account name or password of the application pool identity.
System resources failed to process the maximum number of worker processes.

Why IIS initialization fails:
The configuration section is invalid
It may fail to load a module DLL listed because of invalid path.

Application crash:
One of the savior reasons might also be a module, or application component has produced a debug break, or memory access violation, which makes the process to stop suddenly.

One of above options will help you to troubleshoot the root cause of the error.

[bigdog]

Once you are looking through the logs how do you determine which of the many reasons is causing worker process failure. Are there any big signs or is it just a matter of going through one at a time to figure it out?

[theseowork]

Just login in your hosting panel . Do start Application pool .

[mountainman]

We may be able to temporarily work around this problem by restarting the IIS admin service from the services snap in or from the computer management snap in.