Monitoring App Service instances using Health check is a crucial aspect of maintaining the availability and reliability of your web applications hosted on Azure App Service. Health check enables you to proactively identify and address potential issues with your app instances, ensuring that your users have a seamless experience.
How Health Check Works
Health check works by sending HTTP requests to a specified endpoint on your application at regular intervals. The application's response to these requests indicates its health status. If an instance fails to respond within a certain timeframe or returns an unhealthy status code, App Service considers it unhealthy and removes it from the load balancer. This prevents users from being routed to unresponsive or malfunctioning instances.
Enabling Health Check
Enabling Health check is a straightforward process:
Navigate to the Azure portal and select your App Service app.
Under the "Monitoring" section, choose "Health check."
Click the "Enable" button.
Provide a valid URL path on your application, such as /health or /api/health. This path will serve as the endpoint for Health check to send its requests.
Click "Save."
Customizing Health Check Settings
Once Health check is enabled, you can customize its settings to fine-tune its behavior:
- Interval: Adjust the frequency at which Health check sends requests to your application.
- Threshold: Set the number of consecutive failed requests before an instance is considered unhealthy.
- Timeout: Specify the maximum time allowed for an instance to respond to a Health check request.
- Healthy status codes: Define the HTTP status codes that indicate a healthy instance.
Monitoring Instance Status
After enabling Health check, you can monitor the status of your application instances through the "Instances" tab. This tab displays the name, status, and restart option for each instance. If an instance is deemed unhealthy, you can restart it manually using the provided button.
Benefits of Using Health Check
Implementing Health check offers several advantages for managing your App Service instances:
- Proactive issue detection: Health check identifies unhealthy instances before they impact users.
- Automatic load balancer adjustment: Unhealthy instances are removed from the load balancer, preventing users from being routed to them.
- Reduced downtime: Issues are detected and addressed promptly, minimizing downtime for your application.
- Improved user experience: Users encounter a consistently responsive and reliable application.
In conclusion, Health check is an essential tool for maintaining the health and availability of your App Service instances. By proactively monitoring and addressing potential issues, you can ensure a seamless and enjoyable experience for your users.
Note
- Health check doesn't follow 302 redirects.
- At most one instance will be replaced per hour, with a maximum of three instances per day per App Service Plan.
- If your health check is giving the status Waiting for health check response then the check is likely failing due to an HTTP status code of 307, which can happen if you have HTTPS redirect enabled but have HTTPS Only disabled.
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