numbat-powered metrics emitter

Usage no npm install needed!

<script type="module">
  import numbatEmitter from '';



Numbat-powered metrics emitter. See numbat-collector for the matching metrics collector.

on npm Tests Coverage Status Dependencies


var Emitter = require('numbat-emitter');

var emitter = new Emitter({
    uri: 'tcp://localhost:8000',
    app: 'www',
    node: 'www:8081'
emitter.metric({ name: 'httpd.latency', value: 30 });
emitter.metric({ name: 'disk.used.percent', value: 36 });
emitter.metric({ name: 'heartbeat'});

// if you don't have a reference to an emitter, you
// can broadcast a metric to a global emitter:
process.emit('metric', { name: 'heartbeat' });

See the examples/ directory for working examples.


The constructor requires an options object with an app name in the app field and some manner of specifying where to emit the metrics. You can specify the protocol, host, and port in handy url-parseable format: tcp://, udp://localhost:5000, socket:/tmp/foozle.sock, ws://localhost:5000, nsq://, statsd:// Do this in the uri field of the options object.

Config options:

option description required? default
uri uri of the metrics collector either this or path
path path to the unix domain socket where the collector is listening either this or uri
app name of this service or app; every metric name will be prefixed with it y
node name of this specific app instance
maxretries number of times to retry connecting before giving up 100
maxbacklog max number of metrics to hold in backlog during reconnects 1000
shouldUnref should numbat avoid holding the process open if its the only active conn? true

An example:

    uri:  'udp://localhost:8000',
    app: 'udp-emitter',
    node: 'emitter-1',
    maxretries: 10,
    maxbacklog: 200,

Or numbat might be listening via a unix domain socket:

    path: '/tmp/numbat-collector.sock',
    app: 'socket-emitter'

For complete working emitters, see the examples directory.


Valid events look like this:

    name: 'name.of.metric',
    value: 42
    status: 'okay' | 'warning' | 'critical' | 'unknown',
    description: 'textual description',
    ttl: ms-to-live,
    // fields provided for you
    app: 'appname-from-options',
    host: os.hostname(),
    time: ts-in-ms,

You can add any fields you like & they will be persisted in InfluxDB. However, only the fields listed above are meaningful to the analyzer. Those fields are described in detail below.

NOTE: You can of course emit any events you like! The style of events required/expected by numbat's analyzer, however, might change in development.


String. Required. Name of this event or metric. Use dots . to separate namespaces. If you do not prefix the metric name with yourapp., numbat will do this for you.


Number. Optional. Timestamp in milliseconds since the epoch. If you do not pass a time field, one will be created for you with


Number. Optional. The value of this metric, if appropriate. If you do not pass a value field, it will be defaulted to 1.


String. Optional. One of okay, warning, critical, or unknown. Use this to trigger alerts if this event represents a known-bad condition.


Textual description of the event. Max 255 bytes. Optional.


Number. Optional. Milliseconds that this event is considered valid. The analyzer will expire the event after event.time + event.ttl.

Practical event examples

See also the example emitter in example.js.

var e1 = {
    name: 'request.latency',
    value: 42
    status: 'okay',
var e2 = {
    name: 'request.latency',
    value: 5023
    status: 'warning',

var e3 = { name: 'heartbeat', ttl: 30000 };


Yes, please do! See our contributing guide for basic rules of engagement.