OpenCensus Core Node.js

Node Version dependencies Status devDependencies Status

OpenCensus for Node.js is an implementation of OpenCensus, a toolkit for collecting application performance and behavior monitoring data. It currently includes 3 apis: stats, tracing and tags.

The library is in alpha stage and the API is subject to change.

Installation

Install the opencensus-core package with NPM:

npm install @opencensus/core

Usage

Get the global Stats manager instance.

To enable metrics, we’ll import a few items from OpenCensus Core package.

const { globalStats, MeasureUnit, AggregationType, TagMap } = require('@opencensus/core');

// The latency in milliseconds
const mLatencyMs = globalStats.createMeasureDouble(
  "repl/latency",
  MeasureUnit.MS,
  "The latency in milliseconds"
);

Create Views and Tags:

We now determine how our metrics will be organized by creating Views. We will also create the variable needed to add extra text meta-data to our metrics – methodTagKey, statusTagKey, and errorTagKey.

const methodTagKey = { name: "method" };
const statusTagKey = { name: "status" };
const errorTagKey = { name: "error" };

// Create & Register the view.
const latencyView = globalStats.createView(
  "demo/latency",
  mLatencyMs,
  AggregationType.DISTRIBUTION,
  [methodTagKey, statusTagKey, errorTagKey],
  "The distribution of the latencies",
  // Bucket Boundaries:
  // [>=0ms, >=25ms, >=50ms, >=75ms, >=100ms, >=200ms, >=400ms, >=600ms, >=800ms, >=1s, >=2s, >=4s, >=6s]
  [0, 25, 50, 75, 100, 200, 400, 600, 800, 1000, 2000, 4000, 6000]
);
globalStats.registerView(latencyView);

Recording Metrics:

Now we will record the desired metrics. To do so, we will use globalStats.record() and pass in measurements.

const [_, startNanoseconds] = process.hrtime();
const tags = new TagMap();
tags.set(methodTagKey, { value: "REPL" });
tags.set(statusTagKey, { value: "OK" });

globalStats.record([{
  measure: mLatencyMs,
  value: sinceInMilliseconds(startNanoseconds)
}], tags);

function sinceInMilliseconds(startNanoseconds) {
  const [_, endNanoseconds] = process.hrtime();
  return (endNanoseconds - startNanoseconds) / 1e6;
}

Measures can be of type Int64 or DOUBLE, created by calling createMeasureInt64 and createMeasureDouble respectively. Its units can be:

MeasureUnit	Usage
`UNIT`	for general counts
`BYTE`	bytes
`KBYTE`	Kbytes
`SEC`	seconds
`MS`	millisecond
`NS`	nanosecond

Views can have agregations of type SUM, LAST_VALUE, COUNT and DISTRIBUTION. To know more about Stats core concepts, please visit: https://opencensus.io/core-concepts/metrics/

See Quickstart/Metrics for a full example of registering and collecting metrics.

Useful links

For more information on OpenCensus, visit: https://opencensus.io/
To checkout the OpenCensus for Node.js, visit: https://github.com/census-instrumentation/opencensus-node
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