NestJS Prometheus

• Installation
• Usage
  • Changing the metrics http endpoint
  • Disabling default metrics collection
  • Configuring the default metrics
• Injecting individual metrics
• Available metrics
  • Counter
  • Gauge
  • Histogram
  • Summary
• Providing a custom controller

Installation

yarn add @willsoto/nestjs-prometheus prom-client

npm install @willsoto/nestjs-prometheus prom-client

Usage

import { Module } from "@nestjs/common";
import { PrometheusModule } from "@willsoto/nestjs-prometheus";

@Module({
  imports: [PrometheusModule.register()],
})
export class AppModule {}

By default, this will register a /metrics endpoint that will return the default metrics.

Changing the metrics http endpoint

import { Module } from "@nestjs/common";
import { PrometheusModule } from "@willsoto/nestjs-prometheus";

@Module({
  imports: [
    PrometheusModule.register({
      path: "/mymetrics",
    }),
  ],
})
export class AppModule {}

Disabling default metrics collection

import { Module } from "@nestjs/common";
import { PrometheusModule } from "@willsoto/nestjs-prometheus";

@Module({
  imports: [
    PrometheusModule.register({
      defaultMetrics: {
        enabled: false,
      },
    }),
  ],
})
export class AppModule {}

Configuring the default metrics

import { Module } from "@nestjs/common";
import { PrometheusModule } from "@willsoto/nestjs-prometheus";

@Module({
  imports: [
    PrometheusModule.register({
      defaultMetrics: {
        // See https://github.com/siimon/prom-client#configuration
        config: {},
      },
    }),
  ],
})
export class AppModule {}

Injecting individual metrics

// module.ts
import { Module } from "@nestjs/common";
import {
  PrometheusModule,
  makeCounterProvider,
} from "@willsoto/nestjs-prometheus";
import { Service } from "./service";

@Module({
  imports: [PrometheusModule.register()],
  providers: [
    Service,
    makeCounterProvider({
      name: "metric_name",
      help: "metric_help",
    }),
  ],
})
export class AppModule {}

// service.ts
import { Injectable } from "@nestjs/common";
import { Counter } from "prom-client";
import { InjectMetric } from "@willsoto/nestjs-prometheus";

@Injectable()
export class Service {
  constructor(@InjectMetric("metric_name") public counter: Counter<string>) {}
}

Available metrics

Counter

import { makeCounterProvider } from "@willsoto/nestjs-prometheus";

Gauge

import { makeGaugeProvider } from "@willsoto/nestjs-prometheus";

Histogram

import { makeHistogramProvider } from "@willsoto/nestjs-prometheus";

Summary

import { makeSummaryProvider } from "@willsoto/nestjs-prometheus";

Providing a custom controller

If you need to implement any special logic or have access to the controller (e.g., to customize Swagger), you can provide your own controller (or subclass) of the default controller.

Here is a basic example which should be enough to extend or customize in any way you might need.

// my-custom-controller.ts
import { PrometheusController } from "@willsoto/nestjs-prometheus";
import { Controller, Get, Res } from "@nestjs/common";
import { Response } from "express";

@Controller()
class MyCustomController extends PrometheusController {
  @Get()
  async index(@Res() response: Response) {
    await super.index(response);
  }
}

import { Module } from "@nestjs/common";
import { PrometheusModule } from "@willsoto/nestjs-prometheus";
import { MyCustomController } from "./my-custom-controller";

@Module({
  imports: [
    PrometheusModule.register({
      controller: MyCustomController,
    }),
  ],
})
export class AppModule {}