This article provides guidance on how to troubleshoot common issues encountered with Azure App Service. We will cover a range of scenarios, from deployment problems to runtime errors and performance bottlenecks.

Table of Contents

Common Deployment Issues

Deployment failures can occur for various reasons. Here are some frequent culprits:

  • Configuration Errors: Ensure your connection strings, app settings, and environment variables are correctly configured for the Azure environment.
  • Build Issues: Verify that your application builds successfully locally before deploying. Check for missing dependencies or incompatible packages.
  • Deployment Slot Problems: Issues with deployment slots can lead to unexpected behavior. Always check the deployment logs for slot-specific errors.
  • Code Conflicts: Ensure there are no conflicting files or configurations when deploying to App Service.

Runtime Errors and Exceptions

Runtime errors are when your application runs but encounters unexpected problems.

Application Startup Failures

If your application fails to start, check the following:

  • Application Logs: The most crucial place to start. Access Kudu console or Application Insights for detailed logs.
  • Startup Commands: If you have specific startup commands, ensure they are correct and executable.
  • Dependencies: Make sure all necessary libraries and frameworks are correctly installed and accessible.

Important Note

Many startup issues can be identified by checking the stdout and stderr logs, which are often more detailed than HTTP error messages.

HTTP Request Failures (5xx errors)

A 5xx error indicates a server-side problem. Common causes include:

  • Unhandled Exceptions: Your code is throwing an exception that is not caught.
  • Resource Exhaustion: The application might be running out of memory or CPU.
  • Database Connectivity: Issues connecting to your database can cause requests to fail.
  • External Service Dependencies: If your app relies on external APIs or services, their unavailability can lead to 5xx errors.

HTTP Error 500.0 - Internal Server Error
C:\Program Files\IIS Express\config\app.config

Performance Bottlenecks

Slow performance can be frustrating for users and impact your service's reliability.

High CPU Usage

High CPU can be caused by inefficient algorithms, infinite loops, or resource-intensive background tasks. Use the App Service Diagnostic tools to identify the processes consuming the most CPU.

Memory Leaks

A memory leak occurs when an application fails to release memory that is no longer needed. Monitor memory usage over time. If it continuously increases without plateauing, a leak is likely.

Slow Response Times

This can be a symptom of many underlying issues:

  • Database Queries: Optimize slow database queries.
  • Large Payloads: Minimize data transferred between the client and server.
  • External API Calls: Slow responses from external services.
  • Inefficient Code: Performance profiling can help pinpoint slow code paths.

Tip

Consider using caching mechanisms for frequently accessed data to improve response times.

Networking Issues

Problems with network connectivity can manifest in various ways:

  • Firewall Rules: Ensure your VNet or NSG rules allow traffic to and from your App Service.
  • DNS Resolution: Verify that your custom domain is resolving correctly.
  • SSL Certificates: Expired or misconfigured SSL certificates will prevent secure connections.

Leveraging Azure Diagnostics Tools

Azure provides powerful tools to help you diagnose and troubleshoot your App Service:

  • Diagnose and Solve Problems: Found in the Azure portal for your App Service, this tool offers automated troubleshooting for common issues.
  • Application Insights: Provides deep insights into your application's performance, availability, and usage. Monitor exceptions, track requests, and analyze dependencies.
  • Log Streaming: Real-time access to your application's log files.
  • Kudu Console: An advanced tool providing file system access, process management, and diagnostic capabilities.

By systematically applying these troubleshooting steps and utilizing the available Azure tools, you can efficiently resolve most issues related to Azure App Service.

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