Azure app service timeout but can't find it in app insights log

Yi 0 Reputation points
2023-01-29T16:55:55.94+00:00

I have two app services A and B on the same app service plan, and both has application insights turned on. A depends on B, which mean if a use visits A, then A sends a request to B, after A gets response from B, A returns response to user. Sometimes A become super slow for a few hours, then I check A's application insights' app dependency, it shows the response from B is slow. Then I check B application insights' response time, everything looks fine. Both A and B have custom domain, all requests are sent to custom domain. The slow down can recover itself. So it looks it slows down for no reason, and go back to normal for no reason. It looks like there's network issue on B, how to fix it? If not, what can possibly cause this?

Azure App Service
Azure App Service
Azure App Service is a service used to create and deploy scalable, mission-critical web apps.
6,688 questions
{count} votes

3 answers

Sort by: Most helpful
  1. Arun Siripuram 801 Reputation points
    2023-01-29T17:44:34.3266667+00:00

    @Yi

    Thank you for posting your query on Microsoft Q&A.

    The issue with the slow response from B to A could be due to various reasons. Some common causes of slow response times in an application include:

    1. Network Latency: The issue could be due to network latency, which can occur when the data being sent between A and B is taking too long to travel from one point to another.
    2. Overloaded Servers: If B is processing a high number of requests, it could be causing the server to become overloaded, leading to slow response times.
    3. Resource Constraints: The issue could be due to resource constraints, such as low memory or CPU on the server hosting B.
    4. Application Performance: The issue could be related to the performance of the application running on B. A slow database query or a poorly optimized algorithm could cause slow response times.

    To diagnose the issue, you can try the following:

    1. Monitor Network Latency: Use network monitoring tools such as Network Watcher in Azure to monitor network latency between A and B.
    2. Monitor Resource Utilization: Monitor resource utilization on the server hosting B to see if it is the cause of the slow response times.
    3. Analyze Application Performance: Use Azure App Insights or other performance monitoring tools to identify any performance issues with the application running on B.
    4. Test and Debug: Test the communication between A and B using tools such as cURL or Postman to see if there are any issues with the requests or responses.

    Based on the results of these tests, you can determine the cause of the issue and take appropriate action to resolve it.


  2. Luke Murray 10,441 Reputation points MVP
    2023-01-30T04:51:02.4966667+00:00

    Hi, Yi

    Check to make sure that the App Services are set to: Always On.

    1. Sign in to Azure Management Console.
    2. Navigate to App Services blade at https://portal.azure.com/#blade/HubsExtension/BrowseResourceBlade/resourceType/Microsoft.Web%2Fsites.
    3. Click on the name of the App Services web application that you want to examine.
    4. In the navigation panel, under Settings, choose Configuration and select the General settings tab to access the platform configuration settings available for the selected application.
    5. On the General settings panel, under Platform settings, check the Always on configuration setting. If the setting is turned Off, the Always On feature is currently disabled for the selected Microsoft Azure App Services web application.

    Turn it On.

    It may take a while for them to start, from a cool start, when the requests first get hit


  3. Yi 0 Reputation points
    2023-04-13T21:50:29.7866667+00:00

    It's Azure's network issue. Worked with Azure support for 2 weeks but no solution. I got around it by using vnet, otherwise no solution.

    0 comments No comments