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    10.0.0 • Public • Published


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    Prometheus metrics exporter for Fastify.

    This plugin uses prom-client under the hood.

    This plugin also adds two http metrics for your routes:

    • Requests duration histogram
    • Requests duration summary


    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
    • v9.x.x - supports fastify-4.x prom-client-14.x

    Notable changes


    • Replace route context.config with routeConfig due to deprecation in fastify v4 and removal in fastify v5. If you had disableMetrics option in you route config, update fastify to latest version.


    • Fastify v4 support.
    • Complete config rewrite, default behaviour changed.
    • Support disabling metrics in route config.
    • Now collects metrics only for registered routes by default.
    • Unknown routes metrics collection disabled by default.
    • Removed metrics from request. Now it uses WeakMap and not exposed.
    • Add balcklisting possibility for request methods.
    • Registry overrides moved to metric configuration.
    • Support overriding all Summary and Histogram options for default route metrics.


    • 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.


    npm i fastify-metrics --save
    pnpm 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 >=4.0.0.
    • Node.js >=16.0.0.

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    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');
    await 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.

    Registry clear

    After calling registry.clear() all metrics are removed from registry. In order to add them again to the registry, call fastify.mterics.initMetricsInRegistry.

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    Plugin options

    See for details docs

    Property Type Default Value
    defaultMetrics? IDefaultMetricsConfig { enabled: true }
    endpoint? string | null | Fastify.RouteOptions '/metrics'
    name? string 'metrics'
    routeMetrics? IRouteMetricsConfig { enabled: true }

    Route metrics

    Property Type Default Value
    enabled? boolean true
    groupStatusCodes? boolean false
    invalidRouteGroup? string '__unknown__'
    methodBlacklist? readonly string[] ['HEAD','OPTIONS','TRACE','CONNECT',]
    overrides? IRouteMetricsOverrides
    registeredRoutesOnly? boolean true
    routeBlacklist? readonly string[] []
    Route metrics overrides

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

    const fastify = require('fastify');
    const app = fastify();
    const metricsPlugin = require('fastify-metrics');
    await app.register(metricsPlugin, {endpoint: '/metrics', {
      routeMetrics: {
        overrides: {
          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],
    Property Type Default value
    method? string 'method'
    route? string 'route'
    status? string 'status_code'
    Request durations summary
    Property Type Default value
    name? string 'http_request_summary_seconds'
    help? string 'rrequest duration in seconds summary'
    percentiles? number[] [0.5, 0.9, 0.95, 0.99]
    Request durations histogram
    Property Type Default value
    name? string 'http_request_duration_seconds'
    help? string 'request duration in seconds'
    buckets? number[] [0.05, 0.1, 0.5, 1, 3, 5, 10]

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    HTTP routes metrics in Prometheus

    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_summary_seconds method, route, status_code Requests duration percentiles
    http_request_summary_seconds_count method, route, status_code Requests total count

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    API Docs

    See docs.

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    See changelog.

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    See also

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    Licensed under MIT.

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    npm i fastify-metrics

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    • m03geek