OpenTelemetry Custom Metrics for NestJS
Description
OpenTelemetry module for Nest.
Install
npm i opentelemetry-custom-metrics @opentelemetry/sdk-node --save
Other required dependencies for Prometheus config:
@opentelemetry/exporter-prometheus
Usage
Create otelSDK.ts file
import * as process from 'process';
import { NodeSDK } from '@opentelemetry/sdk-node';
import { PrometheusExporter } from '@opentelemetry/exporter-prometheus';
import { AsyncLocalStorageContextManager } from '@opentelemetry/context-async-hooks';
const otelSDK = new NodeSDK({
metricReader: new PrometheusExporter({
port: 8081,
}),
contextManager: new AsyncLocalStorageContextManager(),
});
export default otelSDK;
process.on('SIGTERM', () => {
otelSDK
.shutdown()
.then(
() => console.log('SDK shut down successfully'),
(err) => console.log('Error shutting down SDK', err),
)
.finally(() => process.exit(0));
});
Add otelSDK to your main.ts
import otelSDK from './otelSDK';
async function bootstrap() {
await otelSDK.start();
...
Import OpenTelemetryCustomMetricsModule in your app.module.ts
import { OpenTelemetryCustomMetricsModule } from 'opentelemetry-custom-metrics';
@Module({
imports: [
OpenTelemetryCustomMetricsModule.forRootAsync(),
...
Add decorators to your methods
app.controller.ts
import { AccessMetric, TimeToProcessMetric } from 'opentelemetry-custom-metrics';
@AccessMetric()
@TimeToProcessMetric()
public async handle(): Promise<void> {
Available decorators:
@AccessMetric() - counts the number of times a method is called
@TimeToProcessMetric() - exposes a gauge and a histogram with the time it took to process the method (time spent on async calls is not included)
Add your own custom metrics
import { MetricService, MetricType } from 'opentelemetry-custom-metrics';
constructor(private metricService: MetricService) {
this.metricService.addCounter('my_counter');
this.metricService.addHistogram('my_histogram');
this.metricService.addObservableCounter('my_observable_counter');
this.metricService.addObservableGauge('my_observable_gauge');
this.metricService.addUpDownCounter('my_up_down_counter');
this.metricService.addObservableUpDownCounter('my_observable_up_down_counter');
}
handle() {
...
this.metricService.observe('my_counter', 1);
this.metricService.observe('my_histogram', 10);
this.metricService.observe('my_observable_counter', 1);
this.metricService.observe('my_observable_gauge', 10);
this.metricService.observe('my_up_down_counter', 1);
this.metricService.observe('my_observable_up_down_counter', 1);
}
Go to http://localhost:8081/metrics to see the metrics