Picture: Microsoft

Bad Gateway error on App Service deployment

Our deployment ran smooth for weeks. But suddenly and without warning and only for one app, the "Bad Gateway" error appeared when deploying Azure DevOps to Azure App Service.

2021-10-02T18:22:51.9578529Z ##[section]Starting: Deploy to !!! PROD STAGE !!!
2021-10-02T18:22:51.9717826Z ==============================================================================
2021-10-02T18:22:51.9718244Z Task         : Azure App Service deploy
2021-10-02T18:22:51.9718657Z Description  : Deploy to Azure App Service a web, mobile, or API app using Docker, Java, .NET, .NET Core, Node.js, PHP, Python, or Ruby
2021-10-02T18:22:51.9719036Z Version      : 4.184.4
2021-10-02T18:22:51.9719264Z Author       : Microsoft Corporation
2021-10-02T18:22:51.9719571Z Help         : https://aka.ms/azureappservicetroubleshooting
2021-10-02T18:22:51.9720056Z ==============================================================================
2021-10-02T18:22:52.5969763Z Got service connection details for Azure App Service:'mypage'
2021-10-02T18:23:54.6310344Z Package deployment using ZIP Deploy initiated.
2021-10-02T18:24:52.6365880Z ##[error]Failed to deploy web package to App Service.
2021-10-02T18:24:52.6380801Z ##[error]Error: Error: Failed to deploy web package to App Service. Bad Gateway (CODE: 502)
2021-10-02T18:24:53.9605307Z Successfully added release annotation to the Application Insight :mypage
2021-10-02T18:24:54.1466996Z ##[warning]Error: Failed to update deployment history. Error: Bad Gateway (CODE: 502)
2021-10-02T18:24:54.4910095Z App Service Application URL: https://myurl.azurewebsites.net
2021-10-02T18:24:54.5026817Z ##[section]Finishing: Deploy to !!! PROD STAGE !!!

Spent a lot of time with Google on what this error could be. Many wrote to reset the App Service Plan, move the app to another region, but in the end it was very simple:

Just manually select a different app scale size (for example, from S1 to P1V3) and then switch back again. Suddenly everything worked again... ¯_(ツ)_/¯