NginxHighHttp4xxErrorRate

NginxHighHttp4xxErrorRate #

Too many HTTP requests with status 4xx (> 5%)

Alert Rule
alert: NginxHighHttp4xxErrorRate
annotations:
  description: |-
    Too many HTTP requests with status 4xx (> 5%)
      VALUE = {{ $value }}
      LABELS = {{ $labels }}    
  runbook: https://srerun.github.io/prometheus-alerts/runbooks/knyar-nginx-exporter/nginxhighhttp4xxerrorrate/
  summary: Nginx high HTTP 4xx error rate (instance {{ $labels.instance }})
expr: sum(rate(nginx_http_requests_total{status=~"^4.."}[1m])) / sum(rate(nginx_http_requests_total[1m]))
  * 100 > 5
for: 1m
labels:
  severity: critical

Here is the runbook for the NginxHighHttp4xxErrorRate alert:

Meaning #

The NginxHighHttp4xxErrorRate alert is triggered when the rate of HTTP requests with a 4xx status code exceeds 5% of the total HTTP requests in the last 1 minute. This alert indicates that there is a problem with the Nginx configuration, the upstream services, or the clients making requests to Nginx.

Impact #

If this alert is not addressed, it may lead to:

  • High error rates for users, resulting in a poor user experience
  • Increased latency and response times for successful requests
  • Potential security vulnerabilities if the error is caused by a misconfigured Nginx setup
  • Increased load on the Nginx server and upstream services, leading to performance degradation or even crashes

Diagnosis #

To diagnose the root cause of the error, follow these steps:

  1. Check the Nginx error logs to identify the specific 4xx error codes and the URLs or IP addresses associated with them.
  2. Review the Nginx configuration files to ensure that they are valid and correctly configured.
  3. Verify that the upstream services are healthy and responding correctly.
  4. Check the client-side logs to see if there are any issues with the requests being sent to Nginx.
  5. Use tools like nginx -t to test the Nginx configuration and nginx -s reload to reload the configuration without restarting Nginx.

Mitigation #

To mitigate the issue, follow these steps:

  1. Identify and fix any configuration issues in the Nginx setup.
  2. Investigate and resolve any issues with the upstream services.
  3. Debug and fix any client-side issues that may be causing the 4xx errors.
  4. Implement rate limiting or IP blocking to prevent abuse or malicious traffic.
  5. Consider implementing a caching layer or content delivery network (CDN) to reduce the load on the Nginx server and upstream services.
  6. Monitor the error rate and response times to ensure that the issue is resolved and does not reoccur.

Note: This runbook provides general guidance and may need to be tailored to the specific environment and configuration of your Nginx setup.

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