App Services slot swap fails

Question

App Services slot swap fails

Youri van der Zee 0

Hi,

20% of our swap slot operation in Github actions fail for some unknown reason, for all our app services.. How do we go about debugging this?

Praneeth Maddali 5,340 Reputation points Microsoft External Staff Moderator

2026-02-13T11:09:22.9766667+00:00
Hi @Youri van der Zee

Before we move forward, could you provide a few details?

What is the exact error message you see when the slot swap fails in GitHub Actions?

How are you performing the swap—using Azure CLI, the portal, or a specific GitHub Action?

Is there any warm-up or health check configured, such as WEBSITE_SWAP_WARMUP_PING_PATH?

When the failures happen, are there any other operations in progress, like deployments, restarts, or configuration or certificate changes?

This information will help us determine if the issue is related to warm-up, concurrency, or the platform.
Hugo Blok 20 Reputation points

2026-02-13T11:34:45.8766667+00:00
@Praneeth Maddali Dear Parneeth, Youri and I are working on the same project so I can add some context.

Run az webapp deployment slot swap \

az webapp deployment slot swap \

--resource-group dev \

--name dev-db-app \

--slot stage \

--target-slot production

shell: /usr/bin/bash -e {0}

ERROR: Cannot swap site slots for site 'dev-db-app' because the 'stage' slot did not respond to http ping.

Error: ``Process completed with exit code 1.

We are using a Github action, where in we are using Azure CLI commands such as the command shown in topic 1

No we haven't added any warm up or health checks

No this, issue occurs wether or not other operations are running, this is not an issue with slots being called when they are already reserved.
Praneeth Maddali 5,340 Reputation points Microsoft External Staff Moderator

2026-02-13T11:47:48.46+00:00

Hi @Hugo Blokhuis

Your request requires troubleshooting on our end. Kindly raise a new thread for further assistance.
Praneeth Maddali 5,340 Reputation points Microsoft External Staff Moderator

2026-02-16T16:28:27.28+00:00

Hi @Youri van der Zee

Just following up to see if your issue has been resolved or if you had a chance to review my earlier comment?

1 answer

Your answer

Praneeth Maddali 5,340 Reputation points Microsoft External Staff Moderator

2026-02-13T11:09:22.9766667+00:00

Hi @Youri van der Zee

Before we move forward, could you provide a few details?

What is the exact error message you see when the slot swap fails in GitHub Actions?

How are you performing the swap—using Azure CLI, the portal, or a specific GitHub Action?

Is there any warm-up or health check configured, such as WEBSITE_SWAP_WARMUP_PING_PATH?

When the failures happen, are there any other operations in progress, like deployments, restarts, or configuration or certificate changes?

This information will help us determine if the issue is related to warm-up, concurrency, or the platform.
Hugo Blok 20 Reputation points

2026-02-13T11:34:45.8766667+00:00

@Praneeth Maddali Dear Parneeth, Youri and I are working on the same project so I can add some context.

Run az webapp deployment slot swap \

az webapp deployment slot swap \

--resource-group dev \

--name dev-db-app \

--slot stage \

--target-slot production

shell: /usr/bin/bash -e {0}

ERROR: Cannot swap site slots for site 'dev-db-app' because the 'stage' slot did not respond to http ping.

Error: ``Process completed with exit code 1.

We are using a Github action, where in we are using Azure CLI commands such as the command shown in topic 1

No we haven't added any warm up or health checks

No this, issue occurs wether or not other operations are running, this is not an issue with slots being called when they are already reserved.
Praneeth Maddali 5,340 Reputation points Microsoft External Staff Moderator

2026-02-13T11:47:48.46+00:00

Hi @Hugo Blokhuis

Your request requires troubleshooting on our end. Kindly raise a new thread for further assistance.
Praneeth Maddali 5,340 Reputation points Microsoft External Staff Moderator

2026-02-16T16:28:27.28+00:00

Hi @Youri van der Zee

Just following up to see if your issue has been resolved or if you had a chance to review my earlier comment?

Answer 1

To debug the failures in your Azure App Service slot swap operations, you can follow these steps:

Check the Logs: Look into the D:\home\LogFiles\eventlog.xml file for any error messages related to the swap operation. This file logs errors that occur during the swap.
Common Errors: Be aware of common issues that can cause swap failures:
- HTTP Request Timeout: The swap operation waits for 90 seconds for each HTTP request. If it times out after five retries, the operation will stop.
- Local Cache Initialization Failure: If the app content exceeds the local disk quota for the local cache, this can lead to failures. Review the local cache settings.
- Configuration Settings Issues: If the configuration settings are prepared for swap but the swap operation fails, you may need to cancel or complete the swap operation to reset the site to its previous state.
- URL Rewrite Rules: Custom warm-up requests can fail due to certain URL rewrite rules in Web.config. Ensure that your rewrite rules allow warm-up requests to reach the app code.
Testing: Consider simulating a failure scenario by swapping to a broken deployment slot. This can help identify issues in your deployment process and allow you to gather more information about the failures.
Environment Variables: Check if any environment variables or app settings are affecting the swap operation. For example, ensure that settings like AzureWebJobsSecretStorageType are correctly configured.

By systematically checking these areas, you should be able to identify the cause of the swap failures and take appropriate action to resolve them.

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App Services slot swap fails

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