[![Build Status][ci-img]][ci] [![Coverage Status][cov-img]][cov] [![NPM Published Version][npm-img]][npm] ![Node Version][node-img]

OpenTracing API for JavaScript

This library is a JavaScript implementation of Open Tracing API. It is intended for use both on the server and in the browser.

Required Reading

To fully understand this platform API, it's helpful to be familiar with the OpenTracing project and terminology more specifically.

Quick Start

Install the package using npm:

npm install --save opentracing

Example

The package contains an example using a naive MockTracer implementation. To run the example:

npm run example

The output should look something like:

Spans:
    parent_span - 1521ms
        tag 'custom':'tag value'
        tag 'alpha':'1000'
    child_span - 503ms
        tag 'alpha':'200'
        tag 'beta':'50'

Code snippet

In your JavaScript code, add instrumentation to the operations to be tracked. This is composed primarily of using "spans" around operations of interest and adding log statements to capture useful data relevant to those operations.

const http = require('http');
const opentracing = require('opentracing');

// NOTE: the default OpenTracing tracer does not record any tracing information.
// Replace this line with the tracer implementation of your choice.
const tracer = new opentracing.Tracer();

const span = tracer.startSpan('http_request');
const opts = {
    host : 'example.com',
    method: 'GET',
    port : '80',
    path: '/',
};
http.request(opts, res => {
    res.setEncoding('utf8');
    res.on('error', err => {
        // assuming no retries, mark the span as failed
        span.setTag(opentracing.Tags.ERROR, true);
        span.log({'event': 'error', 'error.object': err, 'message': err.message, 'stack': err.stack});
        span.finish();
    });
    res.on('data', chunk => {
        span.log({'event': 'data_received', 'chunk_length': chunk.length});
    });
    res.on('end', () => {
        span.log({'event': 'request_end'});
        span.finish();
    });
}).end();

As noted in the source snippet, the default behavior of the opentracing package is to act as a "no op" implementation. To capture and make the tracing data actionable, the tracer object should be initialized with the OpenTracing implementation of your choice as in the pseudo-code below:

const CustomTracer = require('tracing-implementation-of-your-choice');
const tracer = new CustomTracer();

Usage in the browser

The package contains two bundles built with webpack that can be included using a standard `