Custom Metrics

Expose Metrics

By plugging custom metrics onto your code, you will be able to monitor in-code values, in realtime.

Quick Start

First install tx2 module:

$ npm install tx2

Then create and app called monit.js:

const tx2 = require('tx2') const http = require('http') let meter = tx2.meter({ name : 'req/sec', samples : 1, timeframe : 60 }) http.createServer((req, res) => { meter.mark() res.writeHead(200, {'Content-Type': 'text/plain'}) res.write('Hello World!') res.end() }).listen(6001)

And start it with PM2:

$ pm2 start monit.js

Now show the metrics with the command:

$ pm2 show [app] # pm2 show monit

Note: metrics are in the section “Custom Metrics”.

or you can use the Terminal based interface:

$ pm2 monit

Metrics helper available

Then you can program your very own metrics to track important information. 4 different probes are available:

  • Simple metrics: Values that can be read instantly
    • eg. Monitor variable value
  • Counter: Things that increment or decrement
    • eg. Downloads being processed, user connected
  • Meter: Things that are measured as events / interval
    • eg. Request per minute for a http server
  • Histogram: Keeps a reservoir of statistically relevant values biased towards the last 5 minutes to explore their distribution
    • eg. Monitor the mean of execution of a query into database

API Documentation

Note: Refer to the TX2 API Documentation

Examples

Simple Metric: Simple value reporting

This allows to expose values that can be read instantly.

const tx2 = require('tx2') // Here the value function will be called each second to get the value var metric = tx2.metric({ name : 'Realtime user', value : function() { return Object.keys(users).length } }) // Here we are going to call valvar.set() to set the new value var valvar = tx2.metric({ name : 'Realtime Value' }) valvar.set(23)

Counter: Sequential value change

Values that increment or decrement.

Example to count Active Http Requests:

const tx2 = require('tx2') var http = require('http') var counter = tx2.counter({ name : 'Active requests' }) http.createServer(function (req, res) { counter.inc() req.on('end', function() { // Decrement the counter, counter will eq 0 counter.dec() }) res.writeHead(200, {'Content-Type': 'text/plain'}) res.write('Hello World!') res.end() }).listen(6001)

Meter: Average calculated values

Values that are measured as events / interval.

Example to count number of queries per second:

const tx2 = require('tx2') var http = require('http') var meter = tx2.meter({ name : 'req/sec', samples : 1, timeframe : 60 }) http.createServer(function (req, res) { meter.mark() res.writeHead(200, {'Content-Type': 'text/plain'}) res.write('Hello World!') res.end() }).listen(6001)
Options

samples option is the rate unit. Defaults to 1 sec. timeframe option is the timeframe over which events will be analyzed. Defaults to 60 sec.

Histogram

Keeps a reservoir of statistically relevant values biased towards the last 5 minutes to explore their distribution.

const tx2 = require('tx2') var histogram = tx2.histogram({ name : 'latency', measurement : 'mean' }) var latency = 0 setInterval(function() { latency = Math.round(Math.random() * 100) histogram.update(latency) }, 100)
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