@digikare/nestjs-prom

nestjs-prom v1.x

A prometheus module for Nest.

BREAKING CHANGE

nestjs-prom v0.2.x has been moved to stable/0.2 branch.

To migrate from v0.2 to v1.x please see Migrate from 0.2.x to 1.x

Installation

$ npm install --save @digikare/nestjs-prom prom-client

How to use

Import PromModule into the root ApplicationModule

import { Module } from '@nestjs/common';
import { PromModule } from '@digikare/nestjs-prom';

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

PromModule.forRoot options

Here the options available for PromModule.forRoot:

Option	Type	Default	Description
metricPath	string	/metrics	Path to use to service metrics
withDefaultsMetrics	boolean	true	enable defaultMetrics provided by prom-client
withDefaultController	boolean	true	add internal controller to expose /metrics endpoints
withHttpMiddleware	object	{}	To enable the http middleware for http metrics
withHttpMiddleware.enable	boolean	false	Enable http middleware
withHttpMiddleware.timeBuckets	number[]	[0.005, 0.01, 0.025, 0.05, 0.1, 0.25, 0.5, 1, 2.5, 10]	The time buckets wanted
withHttpMiddleware.pathNormalizationExtraMasks	RegEx[]	[]	The regexp mask for normalization

Setup metric

To setup a metric, the module provide multiple ways to get a metric.

Using PromService and Dependency Injection

By using PromService service with DI to get a metric.

@Injectable()
export class MyService {

  private readonly _counter: CounterMetric;
  private readonly _gauge: GaugeMetric,
  private readonly _histogram: HistogramMetric,
  private readonly _summary: SummaryMetric,

  constructor(
    private readonly promService: PromService,
  ) {
    this._counter = this.promService.getCounter({ name: 'my_counter' });
  }

  doSomething() {
    this._counter.inc(1);
  }

  reset() {
    this._counter.reset();
  }
}

Using Param Decorator

You have the following decorators:

• @PromCounter()
• @PromGauge()
• @PromHistogram()
• @PromSummary()

Below how to use it

import { CounterMetric, PromCounter } from '@digikare/nest-prom';

@Controller()
export class AppController {

  @Get('/home')
  home(
    @PromCounter('app_counter_1_inc') counter1: CounterMetric,
    @PromCounter({ name: 'app_counter_2_inc', help: 'app_counter_2_help' }) counter2: CounterMetric,
  ) {
    counter1.inc(1);
    counter2.inc(2);
  }

  @Get('/home2')
  home2(
    @PromCounter({ name: 'app_counter_2_inc', help: 'app_counter_2_help' }) counter: CounterMetric,
  ) {
    counter.inc(2);
  }
}

import { GaugeMetric, PromGauge } from '@digikare/nest-prom';

@Controller()
export class AppController {

  @Get('/home')
  home(
    @PromGauge('app_gauge_1') gauge1: GaugeMetric,
  ) {
    gauge1.inc(); // 1
    gauge1.inc(5); // 6
    gauge1.dec(); // 5
    gauge1.dec(2); // 3
    gauge1.set(10); // 10
  }
}

Metric class instances

If you want to counthow many instance of a specific class has been created:

@PromInstanceCounter()
export class MyClass {

}

Will generate a counter called: app_MyClass_instances_total

Metric method calls

If you want to increment a counter on each call of a specific method:

@Injectable()
export class MyService {
  @PromMethodCounter()
  doMyStuff() {

  }
}

Will generate a counter called: app_MyService_doMyStuff_calls_total and auto increment on each call

You can use that to monitor an endpoint

@Controller()
export class AppController {
  @Get()
  @PromMethodCounter() // will generate `app_AppController_root_calls_total` counter
  root() {
    // do your stuff
  }

  @Get('/login')
  @PromMethodCounter({ name: 'app_login_endpoint_counter' })  // set the counter name
  login() {
    // do your stuff
  }
}

Metric endpoint

The default metrics endpoint is /metrics this can be changed with the metricPath option

@Module({
  imports: [
    PromModule.forRoot({
      defaultLabels: {
        app: 'my_app',
      },
      metricPath: 'custom/uri',
    }),
  ],
})
export class MyModule

Now your metrics can be found at /custom/uri.

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

API

PromModule.forRoot() options

Option	type	description
withDefaultsMetrics	boolean (default: true)	enable defaultMetrics provided by prom-client
withDefaultController	boolean (default: true)	add internal controller to expose /metrics endpoints
withHttpMiddleware	object	To enable the http middleware for http metrics
withHttpMiddleware.enable	boolean (default: false)	Enable http middleware
withHttpMiddleware.timeBuckets	number[] (default: [0.005, 0.01, 0.025, 0.05, 0.1, 0.25, 0.5, 1, 2.5, 10])	The time buckets wanted
withHttpMiddleware.pathNormalizationExtraMasks	RegEx[]	[]

Decorators

• @PromInstanceCounter() Class decorator, create and increment on each instance created
• @PromMethodCounter() Method decorator, create and increment each time the method is called
• @PromCounter() Param decorator, create/find counter metric
• @PromGauge() Param decorator, create/find gauge metric
• @PromHistogram() Param decorator, create/find histogram metric
• @PromSummary() Param decorator, create/find summary metric

Auth/security

I do not provide any auth/security for /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.

License

MIT licensed