VMs / EC2 High HTTP 5xx Error Rate

Understanding Prometheus and Its Purpose

Prometheus is an open-source systems monitoring and alerting toolkit originally built at SoundCloud. It is designed to record real-time metrics in a time series database, built using a highly dimensional data model. Prometheus is particularly useful for monitoring dynamic cloud environments like VMs and EC2 instances, providing insights into system performance and reliability.

Symptom: High HTTP 5xx Error Rate

One of the alerts you might encounter when using Prometheus is a 'High HTTP 5xx Error Rate'. This alert indicates that your web server is returning a high number of 5xx errors, which are server-side errors indicating that the server failed to fulfill a valid request.

Details About the High HTTP 5xx Error Rate Alert

The 'High HTTP 5xx Error Rate' alert is triggered when the number of HTTP 5xx status codes exceeds a predefined threshold. These errors can be caused by various issues, such as server overload, misconfigurations, or application bugs. Monitoring these errors is crucial as they directly impact user experience and can lead to downtime.

Common Causes of 5xx Errors

• Server Overload: The server is unable to handle the volume of incoming requests.
• Application Bugs: Errors in the application code that cause the server to crash or behave unexpectedly.
• Configuration Issues: Incorrect server or application configurations leading to failures.

Steps to Fix the High HTTP 5xx Error Rate Alert

Step 1: Investigate Server Logs

Start by examining the server logs to identify patterns or specific errors that might indicate the root cause. Logs can provide detailed information about the requests that resulted in 5xx errors.

sudo tail -f /var/log/nginx/error.log

For Apache servers, use:

sudo tail -f /var/log/apache2/error.log

Step 2: Check Server Load

Use monitoring tools to check the server load and resource utilization. High CPU or memory usage might indicate that the server is overloaded.

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Consider scaling your infrastructure if the load is consistently high.

Step 3: Review Application Code

Inspect the application code for bugs that could lead to server errors. Ensure that all dependencies are up-to-date and compatible with your server environment.

Step 4: Verify Configuration Settings

Ensure that your server and application configurations are correct. Misconfigurations can lead to unexpected behavior and errors.

For Nginx, check the configuration with:

sudo nginx -t

For Apache, use:

sudo apachectl configtest

Additional Resources

For more detailed guidance on troubleshooting HTTP 5xx errors, consider visiting the following resources:

• Prometheus Documentation
• Nginx Documentation
• Apache HTTP Server Documentation