Azure App Service Documentation

Troubleshooting Common Azure App Service Issues

This article provides guidance on diagnosing and resolving common problems encountered when using Azure App Service. We'll cover a range of issues, from deployment failures to performance bottlenecks.

1. Deployment Failures

Deployment issues are frequent. Here are some common causes and solutions:

Incorrect connection strings: Ensure your connection strings in Azure App Service match those in your application configuration.
Build errors: Check your build logs for syntax errors or missing dependencies.
Permissions: Verify that the deployment user or service principal has the necessary permissions.
App Service plan limits: Ensure your App Service plan is not hitting resource limits (CPU, memory).

You can find detailed deployment logs in the Azure portal under your App Service's "Deployment Center".

2. Application Crashes or Unresponsiveness

If your application is crashing or not responding, consider the following:

Memory Leaks: Monitor your application's memory usage. Tools like Application Insights can help identify memory leaks.
Uncaught Exceptions: Implement robust error handling and logging. Use Application Insights to capture exceptions.
Infinite Loops: Debug your code to find and fix any infinite loops.
Resource Exhaustion: Check CPU and memory usage in the App Service portal. You might need to scale up or out your App Service plan.

Important: Always enable diagnostic logging for your App Service. This will provide valuable insights when issues arise.

3. Performance Issues

Slow performance can be frustrating. Here's how to investigate:

Database Bottlenecks: Analyze your database queries and indexing strategies.
External API Calls: If your application relies on external services, check their response times.
Inefficient Code: Profile your application to identify slow code paths.
Scaling: Consider scaling your App Service plan to handle increased load.

4. Networking Problems

Connectivity issues can impact your application's accessibility:

Firewall Rules: Ensure any relevant firewall rules (both within Azure and externally) are configured correctly.
Virtual Network Integration: If using VNet integration, verify your subnet configuration and NSGs.
DNS Issues: Confirm your custom domain's DNS records are pointing correctly to your App Service.

5. Using Diagnostic Tools

Azure provides several powerful tools to help you troubleshoot:

Azure Monitor & Application Insights: Essential for tracking performance, errors, and usage.
Diagnose and Solve Problems: A built-in tool in the Azure portal that can automatically detect common issues.
Kudu/SCM Site: Provides advanced diagnostics, file access, and command-line tools for your App Service. Access it via your-app-name.scm.azurewebsites.net.

Pro Tip: Regularly review your App Service logs. Early detection of issues can prevent major outages.

Common Error Codes and Their Meanings

Here are some frequently encountered error codes:


    HTTP 400 Bad Request: The server cannot understand the request.
    HTTP 403 Forbidden: The server refuses to fulfill the request.
    HTTP 404 Not Found: The requested resource could not be found.
    HTTP 500 Internal Server Error: A generic error message when an unexpected condition was encountered.
    HTTP 503 Service Unavailable: The server is not ready to handle the request.

For more in-depth troubleshooting and specific scenarios, please refer to the API Reference and other sections of the Azure App Service documentation.