Spectator-js

Client library for instrumenting applications using a dimensional data model.

Description

This module can be used to instrument an application using timers, gauges, counters, distribution summaries, long task timers, and more complex meter types (like bucket or percentile timers) using a dimensional data model.

The generated metrics are periodically sent to an Atlas Aggregator.

To add Node.js runtime metrics, couple this module with the Spectator Nodemetrics module.

Instrumenting Code

'use strict';

const spectator = require('nflx-spectator');

// Netflix applications can use the spectator configuration node module available
// internally through artifactory to generate the config required by nflx-spectator
function getConfig() {
  return {
    commonTags: {'nf.node': 'i-1234'},
    uri: 'http://atlas.example.org/v1/publish',
    timeout: 1000 // milliseconds 
  }
}

class Response {
  constructor(status, size) {
    this.status = status;
    this.size = size;
  }
}

class Server {
  constructor(registry) {
    this.registry = registry;
    // create a base Id, to which we'll add some dynamic tags later
    this.requestCountId = registry.createId('server.requestCount', {version: 'v1'});
    this.requestLatency = registry.timer('server.requestLatency');
    this.responseSize = registry.distributionSummary('server.responseSizes');
  }
  
  handle(request) {
    const start = this.registry.hrtime();
    
    // do some work based on request and obtain a response
    const res = new Response(200, 64);
    
    // update the counter id with dimensions based on the request. The
    // counter will then be looked up in the registry which should be 
    // fairly cheap, such as a lookup of an id object in a map
    // However, it is more expensive than having a local variable set
    // to the counter
    const counterId = this.requestCountId.withTags({country: request.country, 
        status: res.status});
    this.registry.counter(counterId).increment();
    this.requestLatency.record(this.registry.hrtime(start));
    this.responseSize.record(res.size);
    return res;
  }
}

const config = getConfig();
const registry = new spectator.Registry(config);

class Request {
  constructor(country) {
    this.country = country;
  }
}

// somehow get a request from the user...
function getNextRequest() {
  return new Request('AR');
}

function handleTermination() {
  registry.stop();
}

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

registry.start();

const server = new Server(registry);

for (let i = 0; i < 3; ++i) {
  const req = getNextRequest();
  server.handle(req)
}

registry.stop();