Custom Metrics Configuration

Angie can collect custom numeric metrics in shared memory and expose them via the real-time statistics API at /status/http/metric_zones/. This is provided by the Metric module.

Configuration Steps

1. Define a metric zone in the http block:

   • metric_zone creates a zone with a single metric mode.

   • metric_complex_zone creates a zone with multiple named metrics.

2. Update metrics in request processing with the metric directive. Use a key=value pair (both are complex values), and choose the update stage with on= (request, response, or end).

3. Expose the API with a location:

   location /status/ {
       api /status/http/metric_zones/;
   }
   

Example

Count requests per host and expose the metrics in the API:

http {
    metric_zone requests:128k count;

    server {
        listen 80;

        location / {
            metric requests $host=1;
        }

        location /status/ {
            api /status/http/metric_zones/;
        }
    }
}

Notes

• If expire=on is set on the zone and the shared memory is full, the least recently used entries are expired. If expire=off, new updates are discarded and the discarded counter grows.

• If discard_key is set, metrics from expired entries are aggregated under that key in the API output.

• Keys and values are limited to 255 bytes; longer keys are truncated in the API.

• An empty value is treated as 0, and a non-empty value without a leading number is treated as 1.