@mcf/tracer

Creates a Zipkin tracer for consumption by an Express-based application.

Scope

• [x] Create a tracer

Installation

npm i @mcf/tracer;
# OR
yarn add @mcf/tracer;

Usage

const {createTracer} = require('@mcf/tracer');
// OR
import {createTracer} from '@mcf/tracer';

Basic

import express from 'express';
import {expressMiddleware} from 'zipkin-instrumentation-express';
import {createTracer} from '@mcf/tracer';
const tracer = createTracer();
const server = express();
server.use(expressMiddleware({tracer}));
server.listen();

// access context from anywhere
import {MCF_TRACE_NAMESPACE} from '@mcf/tracer';
import {getNamespace} from 'cls-hooked';
const namespace = getNamespace(MCF_TRACE_NAMESPACE);
// do whatever you want with namespace

Full Configuration (with defaults)

import express from 'express';
import {expressMiddleware} from 'zipkin-instrumentation-express';
import {createTracer} from '@mcf/tracer';
const tracer = createTracer({
  httpHeaders: {},
  localServiceName: 'unknown',
  sampleRate: 0.5,
  syncIntervalMs: 1000,
  serverHost: 'localhost',
  serverPort: '9411',
  serverProtocol: 'http',
});
const server = express();
server.use(expressMiddleware({tracer}));

API

.createTracer(:options)

Creates the tracer instance. The :options parameter has the following schema:

Key	Defaults To	Description	Environment variable
httpHeaders	{}	Additional HTTP headers to be sent to the Zipkin server	-
localServiceName	os.hostname() OR 'unknown'	The identity of the current service	process.env.HOSTNAME
sampleRate	0.5	The frequency of sampling by Zipkin. Settings this to 1.0 may cause your data store behind Zipkin to be populated very quickly. Use higher numbers for testing only	-
syncIntervalMs	1000	Synchronises the data every X milliseconds	-
serverHost	"localhost"	The hostname of your Zipkin service	process.env.ZIPKIN_HOST
serverPort	"9411"	The port on which the Zipkin service is listening to	process.env.ZIPKIN_PORT
serverProtocol	"http"	The string identifier of the protocol your are using. Typically "http" or "https"	process.env.ZIPKIN_PROTOCOL

Changelog

0.0.11

• Use cls-hooked for context implementation

0.0.6

• Added static exports for retrieving a Winston formatter to add context details to the logs
• Release!

0.0.5

• Added static exports for retrieving the context provider middleware
• Added static exports for retrieving the Morgan tokenizers

0.0.4

• Added Morgan tokenizer generator

0.0.3

• Initial release