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

parameter	type	description	default
enableDefaultMetrics	Boolean	Enables collection of default prom-client metrics.	true
enableRouteMetrics	Boolean	Enables collection of fastify route metrics.	true
pluginName	String	Change name which you'll use to access prometheus client instance in fastify.	metrics
interval	Number	Default metrics collection interval in ms.	5000
register	Object	Custom prom-client metrics registry.	undefined
prefix	String	Custom default metrics prefix.	""
endpoint	String	If set, fastify route will be added to expose metrics. If not set you may manually add it afterwards.	undefined
metrics	Object	Allows override default metrics config. See section below.	{}
blacklist	String, RegExp, String[]	Skip metrics collection for blacklisted routes	undefined
groupStatusCodes	Boolean	Groups status codes (e.g. 2XX) if true	false
invalidRouteGroup	String	If set, group any urls not matching a valid fastify route together rather than report individually.	undefined

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.

metric	labels	description
http_request_duration_seconds_count	method, route, status_code	Requests total count
http_request_duration_seconds_bucket	method, route, status_code	Requests durations by bucket
http_request_duration_seconds_sum	method, route, status_code	Requests duration summaries by quantile

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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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