README

OpenTelemetry Metrics SDK

OpenTelemetry metrics allow a user to collect data and export it to a metrics backend like Prometheus.

Installation

npm install --save @opentelemetry/sdk-metrics-base

Usage

Counter

Choose this kind of metric when the value is a quantity, the sum is of primary interest, and the event count and value distribution are not of primary interest. It is restricted to non-negative increments. Example uses for Counter:

count the number of bytes received
count the number of requests completed
count the number of accounts created
count the number of checkpoints run
count the number of 5xx errors.

const { MeterProvider } = require('@opentelemetry/sdk-metrics-base');

// Initialize the Meter to capture measurements in various ways.
const meter = new MeterProvider().getMeter('your-meter-name');

const counter = meter.createCounter('metric_name', {
  description: 'Example of a counter'
});

const attributes = { pid: process.pid };
counter.add(10, attributes);

UpDownCounter

UpDownCounter is similar to Counter except that it supports negative increments. It is generally useful for capturing changes in an amount of resources used, or any quantity that rises and falls during a request.

Example uses for UpDownCounter:

count the number of active requests
count memory in use by instrumenting new and delete
count queue size by instrumenting enqueue and dequeue
count semaphore up and down operations

const { MeterProvider } = require('@opentelemetry/sdk-metrics-base');

// Initialize the Meter to capture measurements in various ways.
const meter = new MeterProvider().getMeter('your-meter-name');

const counter = meter.createUpDownCounter('metric_name', {
  description: 'Example of a UpDownCounter'
});

const attributes = { pid: process.pid };
counter.add(Math.random() > 0.5 ? 1 : -1, attributes);

Observable Gauge

Choose this kind of metric when only last value is important without worry about aggregation. The callback can be sync or async.

const { MeterProvider } = require('@opentelemetry/sdk-metrics-base');

const meter = new MeterProvider().getMeter('your-meter-name');


// async callback - for operation that needs to wait for value
meter.createObservableGauge('your_metric_name', {
  description: 'Example of an async observable gauge with callback',
}, async (observableResult) => {
  const value = await getAsyncValue();
  observableResult.observe(value, { attribute: '1' });
});

function getAsyncValue() {
  return new Promise((resolve) => {
    setTimeout(()=> {
      resolve(Math.random());
    }, 100);
  });
}

// sync callback in case you don't need to wait for value
meter.createObservableGauge('your_metric_name', {
  description: 'Example of a sync observable gauge with callback',
}, (observableResult) => {
  observableResult.observe(getRandomValue(), { attribute: '1' });
  observableResult.observe(getRandomValue(), { attribute: '2' });
});

function getRandomValue() {
  return Math.random();
}

ObservableUpDownCounter

Choose this kind of metric when sum is important and you want to capture any value that starts at zero and rises or falls throughout the process lifetime. The callback can be sync or async.

const { MeterProvider } = require('@opentelemetry/sdk-metrics-base');

const meter = new MeterProvider().getMeter('your-meter-name');

// async callback - for operation that needs to wait for value
meter.createObservableUpDownCounter('your_metric_name', {
  description: 'Example of an async observable up down counter with callback',
}, async (observableResult) => {
  const value = await getAsyncValue();
  observableResult.observe(value, { attribute: '1' });
});

function getAsyncValue() {
  return new Promise((resolve) => {
    setTimeout(()=> {
      resolve(Math.random());
    }, 100);
  });
}

// sync callback in case you don't need to wait for value
meter.createObservableUpDownCounter('your_metric_name', {
  description: 'Example of a sync observable up down counter with callback',
}, (observableResult) => {
  observableResult.observe(getRandomValue(), { attribute: '1' });
});

function getRandomValue() {
  return Math.random();
}

Observable Counter

Choose this kind of metric when collecting a sum that never decreases. The callback can be sync or async.

const { MeterProvider } = require('@opentelemetry/sdk-metrics-base');

const meter = new MeterProvider().getMeter('your-meter-name');

// async callback in case you need to wait for values
meter.createObservableCounter('example_metric', {
  description: 'Example of an async observable counter with callback',
}, async (observableResult) => {
  const value = await getAsyncValue();
  observableResult.observe(value, { attribute: '1' });
});

function getAsyncValue() {
  return new Promise((resolve) => {
    setTimeout(() => {
      resolve(Math.random());
    }, 100)
  });
}

// sync callback in case you don't need to wait for values
meter.createObservableCounter('example_metric', {
  description: 'Example of a sync observable counter with callback',
}, (observableResult) => {
  const value = getRandomValue();
  observableResult.observe(value, { attribute: '1' });
});

function getRandomValue() {
  return Math.random();
}

Histogram

Histogram is a non-additive synchronous instrument useful for recording any non-additive number, positive or negative. Values captured by Histogram.record(value) are treated as individual events belonging to a distribution that is being summarized. Histogram should be chosen either when capturing measurements that do not contribute meaningfully to a sum, or when capturing numbers that are additive in nature, but where the distribution of individual increments is considered interesting.

Useful links

For more information on OpenTelemetry, visit: https://opentelemetry.io/
For more about OpenTelemetry JavaScript: https://github.com/open-telemetry/opentelemetry-js
For help or feedback on this project, join us in GitHub Discussions

License

Apache 2.0 - See LICENSE for more information.

Usage no npm install needed!