README.md

How to use the OpenTelemetry sdk-node for automatic metrics with a Basic Express application

Create a project

mkdir example
npm init -y

Install the required dependencies

npm @opentelemetry/api \
@opentelemetry/exporter-metrics-otlp-http \
@opentelemetry/sdk-node \
@opentelemetry/instrumentation-express \
@opentelemetry/instrumentation-http \
@opentelemetry/resources \
@opentelemetry/semantic-conventions \
express

Use this code for automatic metrics provided by sdk-node

Create a file otel.ts

import { diag, DiagConsoleLogger, DiagLogLevel } from '@opentelemetry/api';

import { NodeSDK, metrics } from '@opentelemetry/sdk-node';
import { error } from 'console';
import { Resource } from '@opentelemetry/resources';
import { ExpressInstrumentation } from '@opentelemetry/instrumentation-express';
import { HttpInstrumentation } from '@opentelemetry/instrumentation-http';
import { SemanticResourceAttributes } from '@opentelemetry/semantic-conventions';
import { OTLPMetricExporter } from '@opentelemetry/exporter-metrics-otlp-http';

diag.setLogger(new DiagConsoleLogger(), DiagLogLevel.DEBUG);

const resource = new Resource({
  [SemanticResourceAttributes.SERVICE_NAME]: process.env.npm_package_name,
});

const metricsExporter = new OTLPMetricExporter();

const sdk = new NodeSDK({
  metricReader: new metrics.PeriodicExportingMetricReader({
    exporter: metricsExporter,
    exportIntervalMillis: 3000,
  }),
  autoDetectResources: true,
  resource: resource,
  instrumentations: [new HttpInstrumentation(), new ExpressInstrumentation()],
});

try {
  sdk.start();
} catch (err) {
  error(err);
}

Note

For some reason we need the following packages, which, according to the documentation they are supposed to be used when looking for Traces. If we remove them, we can't see the default metrics being generated.

import { ExpressInstrumentation } from '@opentelemetry/instrumentation-express';
import { HttpInstrumentation } from '@opentelemetry/instrumentation-http';

Update the package.json to start the sdk

"scripts": {
  "start": "NODE_OPTIONS='--require ./dist/otel.js' node dist/server.js",
}

Run this example

git clone https://github.com/obs-nebula/gamma-ray.git
cd gamma-ray/metrics/01
npm install
npm run build
npm start

Open a new terminal and run

podman-compose up

Open a new terminal and run a few times

curl localhost:8080

Go to prometheus to see the metrics