Azure Appservice plan instance restart does it affect performance

Question

The restarting Azure Appservice plan instance does it affect performance?

when restarting "App Service" the application is not available for few seconds the application (rest api) returns 503.

but when restarting "App service plan instance" the application never fall down.

why?

So The restarting Azure Appservice plan instance really affect performance or not?

Answer 1

I may be late on this, to benefit the community, adding to suggestions outlined by Harshitha in the comment section'.

Firstly, just to highlight, Azure App Service represents a fleet of scale units. An app service always runs in an App Service Plan(ASP).

Based on my understanding of your scenario, restarting a single instance of an Azure App Service will not impact on the (ASP) as it is capable of running multiple instances (if it’s configured to run multiple instances/scaled-out). Consequently, if one instance is restarting, the other instances can still serve your application, ensuring it remains available.

When you restart the App Service/WebApp, the application may not be available for a few seconds (as you mentioned, it may return a 503 error) as expected. This is because the service is temporarily unavailable during the restart process.

Therefore, to answer your question, restarting an ASP instance does not really affect performance, as long as there are multiple instances running.

Having mentioned that, there are other factors that can impact the performance of your App Service/WebApp, such as the size and configuration of your ASP, the number of instances running, and the workload of your web apps. If you're experiencing performance issues, it's a good idea to review these factors and consider scaling up or out your App Service plan or optimizing your web app code to improve performance.

You may wish to check these FAQs:

Can I prepare my apps better for restarts?

How does the upgrade work how does it ensure the smooth operation of my apps?

If your applications need extra time during restarts to come online (a typical pattern would be heavy dependency on external resources during application warm-up/start-up), consider using Health Check.

If I have misunderstood your ask or you need more info, kindly do let us know with additional info about your requirement or issue.

Reference: Azure App Service plan overview