@selinarnd/nest-prom

A Prometheus module for Nest.

Installation

$ yarn add --save @selinarnd/nest-prom prom-client

How to use

Import PromModule into the root ApplicationModule:

import { Module } from "@nestjs/common";
import { PromModule } from "@selinarnd/nest-prom";

@Module({
  imports: [
    PromModule.forRoot({
      defaultLabels: {
        app: 'my_app',
      },
    }),
  ],
})
export class ApplicationModule {}

Setup metric

In your module, use the forMetrics() method to define the metrics needed.

import { Module } from "@nestjs/common";
import { PromModule, MetricType } from "@selinarnd/nest-prom";

@Module({
  imports: [
    PromModule.forMetrics([
      {
        type: MetricType.Counter,
        configuration: {
          name: 'my_counter',
          help: 'my_counter a simple counter',
        },
      },
      {
        type: MetricType.Gauge,
        configuration: {
          name: 'my_gauge',
          help: 'my_gauge a simple gauge',
        },
      },
      {
        type: MetricType.Histogram,
        configuration: {
          name: 'my_histogram',
          help: 'my_histogram a simple histogram',
        },
      },
      {
        type: MetricType.Summary,
        configuration: {
          name: 'my_summary',
          help: 'my_summary a simple summary',
        },
      },
    ]),
  ],
})
export class MyModule {}

And you can use @InjectCounterMetric() decorator to get the metrics:

import { Injectable } from "@nestjs/common";
import {
  InjectCounterMetric,
  InjectGaugeMetric,
  InjectHistogramMetric,
  InjectSummaryMetric,
  CounterMetric,
  GaugeMetric,
  HistogramMetric,
  SummaryMetric,
} from "@selinarnd/nest-prom";

@Injectable()
export class MyService {
  constructor(
    @InjectCounterMetric('my_counter') private readonly counterMetric: CounterMetric,
    @InjectGaugeMetric('my_gauge') private readonly gaugeMetric: GaugeMetric,
    @InjectHistogramMetric('my_histogram') private readonly histogramMetric: HistogramMetric,
    @InjectSummaryMetric('my_summary') private readonly summaryMetric: SummaryMetric,
  ) {}

  doStuff() {
    this.counterMetric.inc();
  }

  resetCounter() {
    this.counterMetric.reset();
  }
}

Metric endpoint

At the moment, no way to configure the /metrics endpoint path.

PS: If you have a global prefix, the path will be {globalPrefix}/metrics.

API

PromModule.forRoot() options

• withDefaultsMetrics: boolean (default true) enable defaultMetrics provided by prom-client
• withDefaultController: boolean (default true) add internal controller to expose a /metrics endpoint
• useHttpCounterMiddleware: boolean (default false) register http_requests_total counter

Auth/security

We do not provide any auth/security for the /metrics endpoints.

This is not the aim of this module, but depending of the auth strategy, you can apply a middleware on /metrics to secure it.

TODO

• Update readme
  • Gauge
  • Histogram
  • Summary
• Manage registries
• Tests
• Give possibility to custom metric endpoint
• Adding example on how to secure /metrics endpoint
  • secret
  • jwt