streamable metrics.

npm install probe-stream
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insert a metric-gathering probe into a set of streams.

var probe = require('probe-stream')({interval: 1000}) //this is the default.


probe will emit updated stream stats every second (by default) on the

actually, probe is a Stream itself! so you can do this:

var es = require('event-stream')


probe is a stream of raw objects, so remember to stringify it.

custom metrics.

by default, probe-stream measures bytes per-second. but it can be used to measure any kind of data coming down the stream.

create new metric formats like this:

var probeStream = require('probe-stream')

var probe = probeStream({
  init: function (measured) {
    return {
      chunks: new measured.Gauge()
  create: function (metrics) {
    var self = this // the probe-stream. a Stream.
    return {
      data: function (data) {
        metrics.chunks.mark() //count another chunk.

init is called once, to set up the metrics that will be used. it must return an object of metrics. It will be passed an instance of measured as the first argument.

create is called whenever you create a probe with probe.createProbe(). create is called in the context of the new probe stream. The first arg is the metrics object that init returned. create should return an object of listeners, these will be assigned to the probe stream, and cleaned up automatically when the stream ends.

You can also assign listeners manually, it's up to you.

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