@last9/openapm

An APM solution based on metrics and open-source tools such as Prometheus and Grafana for NodeJs-based applications.

Table of Contents

1. Installation
2. Usage
3. Options
4. API Reference
5. Setup Locally
6. Grafana Dashboard View

Installation

npm install --save @last9/openapm@latest

Usage

const express = require('express');
const { OpenAPM } = require('@last9/openapm');

const app = express();
const openapm = new OpenAPM();

// Instrument services

app.listen(3000);

const gracefullyShutdown = () => {
  app.close(() => {
    openapm
      .shutdown()
      .then(() => {
        console.log('OpenAPM shutdown successful.');
      })
      .catch((err) => {
        console.log('Error shutting down OpenAPM', err);
      });
  });
};

process.on('SIGINT', gracefullyShutdown);
process.on('SIGTERM', gracefullyShutdown);

1. Express
2. MySQL
3. NestJS
4. Next.js

Express

In the example below, the metrics will be served on localhost:9097/metrics. To change the port, you can update it through the options (See the options documentation).

const { OpenAPM } = require('@last9/openapm');
const openapm = new OpenAPM();

openapm.instrument('express');

MySQL

This currently supports instrumentation for all Node.js ORMs, which are mysql2 compatible.

Ensure to add this line of code before you initialize db connection/pool/poolCluster.

openapm.instrument('mysql');

NestJS

OpenAPM currently supports RED Metrics for NestJS v4 and above.

openapm.instrument('nestjs');

Next.js

OpenAPM supports RED metrics for both pages and app router in a Next.js application.

openapm.instrument('nextjs');

Note: You can only use the library if Next.js runs in a Node.js environment. Since OpenAPM relies on prom-client for capturing metrics data, a serverless environment might not be able persist them.

Options

Usage

const openapm = new OpenAPM({
  // Options go here
});

1. path: The path at which the metrics will be served. For eg. /metrics

2. metricsServerPort: (Optional) The port at which the metricsServer will run.

3. environment: (Optional) The application environment. Defaults to production.

4. defaultLabels: (Optional) Any default labels to be included.

5. requestsCounterConfig: (Optional) Requests counter configuration, same as Counter in prom-client. Defaults to

   {
      name: 'http_requests_total',
      help: 'Total number of requests',
      labelNames: ['path', 'method', 'status'],
    }

6. requestDurationHistogramConfig: (Optional) Requests Duration histogram configuration, the same as Histogram in prom-client. Defaults to

    {
        name: 'http_requests_duration_milliseconds',
        help: 'Duration of HTTP requests in milliseconds',
        labelNames: ['path', 'method', 'status'],
        buckets: promClient.exponentialBuckets(0.25, 1.5, 31),
      }

7. extractLabels: (Optional) Extract labels from URL params (WIP: Headers, Subdomain)

   // To extract from the URL params
   {
      ...
      extractLabels: {
         tenant: { // Here 'tenant' is the label name
            from : 'params',
            key: 'org' // Which key to extract from the params
            mask: ':org' // Replacement string
         }
      }
   }

8. excludeDefaultLabels: (Optional) Provide labels to exclude from the default labels

{
  ...
  excludeDefaultLabels: ['environment', 'version']
}

9. levitateConfig: (Optional) Configuration for Levitate TSDB. Adding this configuration will enable the Change Events.

10. enableMetricsServer: (Optional) Defaults to true. When set to false the OpenAPM won't start a metrics server. To get the metrics users can rely on the .getMetrics() function.

{
   ...
   levitateConfig: {
      host: 'https://app.last9.io',
      orgSlug: 'last9', /** The slug can be obtained from the Last9 dashboard.*/
      dataSourceName: 'data-source', /** The data source can be obtained from the data source pages in the Last9 dashboard*/
      refreshTokens: {
         write: '0d2a1a9a45XXXXXXXXXXXXXX3f1342790d2a1a9a45XXXXXXXXXXXXXX3f1342790d2a1a9a45XXXXXXXXXXXXXX3f134279' /** You can get this from the API access page on Last9 dashboard*/
      }
   }
}

11. enabled: (Optional) Defaults to true. When set to false OpenAPM will be disabled and no metrics will be collected or emitted.

const openapm = new OpenAPM({
  enabled: process.env.NODE_ENV === 'production'
})

12. additionalLabels: (Optional) Accepts an array of label keys that will be emitted with the metrics. This option is used in tandem with the setOpenAPMLabels API. Checkout API Reference

const openapm = new OpenAPM({
  additionalLabels: ['slug']
})

API Reference

1. instrument: Used to instrument supported technologies. Refer the usage section.

2. getMetrics: Returns a Promise of string which contains metrics in Prometheus exposition format. You can use this function to expose a metrics endpoint if enableMetricsServer is set to false. For example,

const openapm = new OpenAPM({
  enableMetricsServer: false
});

openapm.instrument('express');

const app = express();

app.get('/metrics', async (_, res) => {
  const metrics = await openapm.getMetrics();
  res.setHeader('Content-Type', 'text/plain; version=0.0.4; charset=utf-8');
  res.end(metrics);
});

3. shutdown: Returns a promise which is resolved after the cleanup in OpenAPM. The cleanup includes closing the metrics server if it has started and cleared the prom-client register.

const gracefullyShutdown = () => {
  server.close(() => {
    openapm
      .shutdown()
      .then(() => {
        console.log('OpenAPM shutdown successful.');
      })
      .catch((err) => {
        console.log('Error shutting down OpenAPM', err);
      });
  });
};

process.on('SIGINT', gracefullyShutdown);
process.on('SIGTERM', gracefullyShutdown);

4. setOpenAPMLabels: Unlike other APIs. You can directly import setOpenAPMLabels in any file to set custom labels to the request. Make sure to mention the label key in additionalLabels option. This function can set multiple labels in the metrics emitted by the ongoing HTTP request.

Note: setOpenAPMLabels currently works with express and Nest.js only.

import { OpenAPM, setOpenAPMLabels } from '@last9/openapm';

const openapm = new OpenAPM({
  additionalLabels: ['slug']
});

const handler = () => {
  setOpenAPMLabels({ slug: 'org-slug' });
};

5. Defining custom metrics

OpenAPM exposes underlying prom-client via getMetricClient function.

const { getMetricClient } = require('@last9/openapm');

// initialize custom metric
const client = getMetricClient();
const counter = new client.Counter({
  name: 'cancelation_calls',
  help: 'no. of times cancel operation is called'
});

// handler
app.get('/cancel/:ids', (req, res) => {
  counter.inc();
  res.status(200).json({});
});

Follow the documentation of prom-client to get familiar with the DSL for defining custom metrics.

Setup locally

Make sure you are in the express directory.

• Install packages

npm install

• Build package

  • This will build the package and store the JS and type declaration files in the dist folder.

npm run build

Grafana Dashboard View

1. Import this dashboard into your Grafana
2. Select your data source
3. Save the dashboard

About Last9

Last9 builds reliability tools for SRE and DevOps.