HTTP Error 503 - The Service is Unavailable

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When trying to open Orchestrator website, error 503 is received.

The error occurs if the Application Pool is stopped​​​​​​ in IIS. The first thing to do is diagnose why the Application Pool is stopping.

Diagnosing the issue

This error can be diagnosed by restarting the IIS service to see if any errors get generated in the Windows event viewer.

  1. Open a cmd prompt as an administrator.
  2. Run the following command to restart IIS service "iisreset".
  3. Open the application Event Viewer and go to the following location:
    • Event Viewer (Local) -> Windows Logs -> System
  4. One possible problem is that the user account used to define the App Pool Identity is invalid. If this is the case, there will be two warning messages and one error message generated by the "WAS" source. The messages will be something along the lines of:
    • Error: ​​​​Application pool UiPath Orchestrator has been disabled....
    • Warning: ​​​​​Application pool UiPath Orchestrator has been disabled....
    • Warning: The identity of application pool UiPath Orchestrator 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...
  5. Alternatively, if the below error message is generated, access the section labeled: Diagnosing and Resolving IIS Application Pool Termination.
    • Error: Application pool 'UiPath Orchestrator' is being automatically disabled due to a series of failures in the process(es) serving that application pool.
  6. If the above messages were generated, access the section labeled: Fixing the Application Pool Identity.
  7. If the above messages were not generated, try to do the following:
    • Open "run" and type "inetmgr" to open the IIS console.
    • Go to Application Pools and find the Orchestrator Application Pool (most likely it is named "UiPath Orchestrator").
    • Right-click the Application Pool. If the start menu is grayed out, it means the service is running. If it is not grayed out, try starting the service.
    • After the service starts go to the Orchestrator URL
  8. If Orchestrator is now accessible, then either the App Pool Service was manually stopped, or the IIS service intentionally stopped the App Pool service due to process failures. Go to the section labeled: Diagnosing and Resolving IIS Application Pool Termination.
  9. If Orchestrator is not accessible you will still want to go to the section labeled "Diagnosing and Resolving IIS Application Pool Termination".
  10. If the Application Pool did not stop running, check the following logs: %SystemRoot%\System32\LogFiles\HTTPERR.
    • See: https://docs.microsoft.com/en-us/troubleshoot/aspnet/error-logging-http-apis#kinds-of-errors-that-the-http-api-logs
    • Usually, an intermittent 503 will correspond to a QueueFull message in these logs.
    • Open a ticket with UiPath and share these logs. The performance parameters of the server may need to be adjusted.

Fixing the Application Pool Identity

The Application Pool can stop for two reasons related to the Application Pool Identity:
  1. The account under which the Application Pool is running had its password expire, and it was reset. However, the password was not updated for the Application Pool. In this case, consider using an Application Pool Identity Service Account (see Step 2. a) and follow the steps mentioned step c.
  2. The Application Pool is running under the wrong identity (account). To correct this, please follow the steps below
    1. Instead of using a user account, use an Application Pool Identity Service Account. This is Microsoft's recommended approach. It may be necessary to add the Application Pool Identity Service Account to SQL if using Windows Authentication in the database connection.
    2. Go to command prompt → Type "whoami" and confirm the domain/ username logged in. If the logged-in user is supposed to be used for the application pool identity, update it to match.
    3. A service account can also be used for running the application pool, in this case, the IT team should provide the service account to be used.
    4. To update the identity in the Application Pool , follow the steps below:
      • Open "run" and type "inetmgr" to open the IIS console.
      • Go to "Application Pools" and search for "UiPath Orchestrator".
  • Right-click and select "Advanced Settings," and click on the dots to open the window to set the username and password.
  • If using an Application Pool Identity Service Account, select "Built-in account" and choose ApplicationPoolIdentity". If not using a user account or service account, select "Custom Account" and click on "Set " and then provide the username and password to be used. The username should be along with the domain.



Diagnosing and Resolving IIS Application Pool Termination

To determine why the Orchestrator Application Pool stopped running, or why it did not start after a reset of IIS, check the event viewer logs to determine if there is a configuration problem with the Application Pool.
  1. Open the application Event Viewer and go to the following location:
    • ​​​​Event Viewer (Local) -> Windows Logs -> Application
  2. Check for logs generated by the source "Application Error" from around the time Orchestrator stopped working or failed to start. ​​​​​​
  3. Check for an error that contains something along the lines of:
    • Error: Faulting application name: w3wp.exe, version: 10.0.14393.0, time stamp: 0x57899b8a...
  4. If there is no such error, please open a support request with UiPath and include your Application logs and System logs from the event viewer.
  5. If the above error exists, it means that the Application pool does not have enough virtual memory and is faulting to the point that the IIS service shuts the site down. To resolve this, do the following:
    • Open "run" and type "inetmgr" to open the IIS console.
    • Go to "Application Pools" and search for "UiPath Orchestrator"
    • Right Click the Orchestrator Application Pool and go to "Advanced Settings"
    • Scroll down to the section labeled "Private Memory Limit (KB)"
    • If the value for this section is zero it means the memory is unlimited and you may need to increase the resources of your Orchestrator instance. Skip to the last step of this section.
    • If the value is non-zero, ensure it is at least 80% of the total RAM on the server. So, for 8GBs of Ram, the value would be 6,710,886. 80% is usually the recommended amount.
  6. After making the change, restart IIS.
  7. If the issue still occurs, open a support request with UiPath and include the System logs and Application logs from the Event Viewer.
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