Prometheus client for node.js

A prometheus client for node.js that supports histogram, gauges and counters.

Usage

See example folder for a sample usage. The library does not bundle any web framework, to expose the metrics just return the metrics() function in the registry.

API

Configuration

All metric types has 2 mandatory parameters, name and help.

Counter

Counters go up, and reset when the process restarts.

var Client = require('prom-client');
var counter = new Client.counter('metric_name', 'metric_help');
counter.inc(); // Inc with 1
counter.inc(10); // Inc with 10

Gauge

Gauges are similar to Counters but Gauges value can be decreased.

var Client = require('prom-client');
var gauge = new Client.gauge('metric_name', 'metric_help');
gauge.set(10); // Set to 10
gauge.inc(); // Inc with 1
gauge.inc(10); // Inc with 10
gauge.dec(); // Dec with 1
gauge.dec(10); // Dec with 10

There are some utilities for common use cases:

gauge.setToCurrentTime(); // Sets value to current time

var end = gauge.startTimer();
xhrRequest(function(err, res) {
    end(); // Sets value to xhrRequests duration in seconds
});

Histogram

Histograms track sizes and frequency of events.

Configuration

The defaults buckets are intended to cover usual web/rpc requests, this can however be overriden.

var Client = require('prom-client');
new Client.histogram('metric_name', 'metric_help', { 
    buckets: [ 0.10, 5, 15, 50, 100, 500 ]
});

Examples

var Client = require('prom-client');
var histogram = new Client.histogram('metric_name', 'metric_help');
histogram.observe(10); // Observe value in histogram

Utility to observe request durations

var end = histogram.startTimer();
xhrRequest(function(err, res) {
    end(); // Observes the value to xhrRequests duration in seconds
});

Labels

All metrics take an array as 3rd parameter that should include all supported label keys. There are 2 ways to add values to the labels

var Client = require('prom-client');
var gauge = new Client.gauge('metric_name', 'metric_help', [ 'method', 'statusCode' ]);

gauge.set({ method: 'GET', statusCode: '200' }, 100); // 1st version, Set value 100 with method set to GET and statusCode to 200
gauge.labels('GET', '200').set(100); // 2nd version, Same as above