fastify-metrics

Prometheus metrics exporter for Fastify.

This plugin uses prom-client under the hood.

This plugin also adds 2 http metrics for your routes:

• Requests duration histogram
• Requests duration summary

ToC

• fastify-metrics
  • ToC
  • Fastify support
  • Notable changes
    • v6.x.x
  • Installation
  • Features and requirements
  • Usage
    • Plugin options
      • Metrics details
    • HTTP routes metrics
  • Docs
  • Changelog
  • See also
  • License

Fastify support

• v3.x.x - supports fastify-1.x
• v4.x.x - supports fastify-2.x prom-client-11.x
• v5.x.x - supports fastify-2.x prom-client-12.x
• v6.x.x - supports fastify-3.x

Notable changes

v6.x.x

• Fastify v3 support.
• Drop node.js 8 support.
• enableDefaultMetrics - now enables only default prom-client metrics. Set to true by default.
• enableRouteMetrics - additional flag that enables route metrics. Set to true by default.

Installation

npm i fastify-metrics --save

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Features and requirements

• Collects default server metrics (see prom-client);
• Collects route response timings
• Adds metrics to fastify instance for your custom metrics.

• Requires fastify >=3.0.0.
• Node.js >=10.0.0.

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Usage

Add it to your project like regular fastify plugin. Use register method and pass options to it.

const fastify = require('fastify');
const app = fastify();

const metricsPlugin = require('fastify-metrics');
app.register(metricsPlugin, { endpoint: '/metrics' });

It also exports client to fastify instance fastify.metrics.client which you may use it in your routes.

You may create your metrics when app starts and store it in fastify.metrics object and reuse them in multiple routes.

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Plugin options

Metrics details

You may override default metrics settings. You may provide overrides for two metrics tracking http request durations: histogram and summary. Default values:

{
  histogram: {
    name: 'http_request_duration_seconds',
    help: 'request duration in seconds',
    labelNames: ['status_code', 'method', 'route'],
    buckets: [0.05, 0.1, 0.5, 1, 3, 5, 10],
  },
  summary: {
    name: 'http_request_summary_seconds',
    help: 'request duration in seconds summary',
    labelNames: ['status_code', 'method', 'route'],
    percentiles: [0.5, 0.9, 0.95, 0.99],
  },
}

You may also provide registers there or use it instead of prefix. Override should look like:

const fastify = require('fastify');
const app = fastify();
const metricsPlugin = require('fastify-metrics');

app.register(metricsPlugin, {endpoint: '/metrics', {
  histogram: {
    name: 'my_custom_http_request_duration_seconds',
    buckets: [0.1, 0.5, 1, 3, 5],
  },
  summary: {
    help: 'custom request duration in seconds summary help',
    labelNames: ['status_code', 'method', 'route'],
    percentiles: [0.5, 0.75, 0.9, 0.95, 0.99],
  },
}});

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HTTP routes metrics

The following table shows what metrics will be available in Prometheus. Note suffixes like _bucket, _sum, _count are added automatically.

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Docs

See docs.

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Changelog

See changelog.

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See also

• fastify-prom-client - just simple client that adds aggregated http requests metric.

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License

Licensed under MIT.

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