Express-Jaeger

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Jaeger middleware to request tracing for express application

Required Reading

Opentracing

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

Jaeger(One Of Request Tracing System implement Opentracing)

To fully understand Jaeger, it's helpful to be familiar with the Jaeger project and Jaeger Client for Node

Simple Concept

One request map to one trace

One trace atleast has one span which is master span

Master span can have many children spans

Installation

npm i @chankamlam/express-jaeger -S

Architecture of Jaeger Server

for development

for prodution

Build up Jaeger Server Infra locally(development env)

docker run -d -e COLLECTOR_ZIPKIN_HTTP_PORT=9411 -p5775:5775/udp -p6831:6831/udp -p6832:6832/udp \
  -p5778:5778 -p16686:16686 -p14268:14268 -p9411:9411 jaegertracing/all-in-one:latest

Quick Start

const express = require("express");
const jaeger = require("@chankamlam/express-jaeger");
const app = express();

const config = {
    serviceName: 'service1-express',
    sampler: {
        type: "const",
        param: 1
    },
    reporter: {
        collectorEndpoint: "http://localhost:14268/api/traces"
    },
};                                                      // required
const options = { 
  baggagePrefix: "-Johua-",                             // optional,you can let options={}
  excludePath:["/api/v1/health","/api/v1/metric"]       // exclude path
  }; 

app.use(express.json()) // for parsing application/json
app.use(express.urlencoded({ extended: true })) // for parsing application/
x-www-form-urlencoded

app.use(jaeger(config,options,(req,res)=>{
   // here to write your code
   // which is showing here is to auto record query/body/path for every request
    const jaeger = req.jaeger
    jaeger.setTag("route",req.path)
    jaeger.setTag("body",req.body)
    jaeger.setTag("query",req.query)
}));

app.all("/abc", async function (req, res) {
    res.send({code: 200, msg: result});
});

app.listen(3000, '127.0.0.1', function () {
    console.log('start');
});

Usage

normallyUsingSpan2Log

const express = require("express");
const jaeger = require("@chankamlam/express-jaeger")
const app = express();

// setup config, atleast need this param
const config = {
    serviceName: 'aservice-express',                              // your service name
    sampler: {                                                    // setup sampler
        type: "const",
        param: 1
    },
    reporter: {
        collectorEndpoint: "http://localhost:14268/api/traces"    // your jaeger server endpoint
    },
};

// setup options, defaut is {}
const options = { 
  baggagePrefix: "-Johua-",
  excludePath:["/api/v1/health","/api/v1/metric"]                 // exclude path
   };

/*  
 *  using jager,after this it will has one object which called jaeger,
 *  with four properties(span,tracer,request,tags) binding in req
 */
app.use(jaeger(config,options));

app.get("/normallyUsingSpan2Log", async function (req, res) {
    const jaeger = req.jaeger;
    jaeger.log("timestamp",Date.now());
    res.send({code: 200, msg: "success"});
});
app.listen(3000, '127.0.0.1', function () {
    console.log('start server...');
});

usingSpan2LogWithError

app.get("/errorUsingSpan2Log", async function (req, res) {
    const jaeger = req.jaeger;
    const tags = req.jaeger.tags;
    try {
      throw Error("err");           // create exception to test
    } catch (err) {
      jaeger.setTag(tags.ERROR, true);   // diaplay to JaegerUI when you mark tag as "error"
      jaeger.log("errorMsg", err.message);
    }
    res.send({code: 200, msg: "success"});
});

remoteCallingAndlogResult

app.get("/remoteCallingAndlogResult", async function (req, res) {
    const jaeger = req.jaeger
    // for remote request, you have to use jaeger.axios which wrap axios by tracing
    const result = await jaeger
                         .axios({url:"http://localhost:3001/bc"})
                         .then(r=>r.data);
    jaeger.log("result",result)
    res.send({code: 200, msg: "success"});
});

remoteCallingAndlogResultInTwoSpan

app.get("/remoteCallingAndlogResultInTwoSpan", async function (req, res) {

    const jaeger = req.jaeger

    // default under master span (auto create by every request)
    const span1 = jaeger.createSpan("resut1")
    const result1 = await jaeger
                          .axios({url:"http://localhost:3001/a"})
                          .then(r=>r.data);
    span1.log("result1",result1)
    span1.finish();

    // default under master span (auto create by every request)
    const span2 = jaeger.createSpan("resut2")
    const result2 = await jaeger
                          .axios({url:"http://localhost:3001/b",method:"post",data:{}})
                          .then(r=>r.data);
    span2.log("result2",result2)
    span2.finish();

    jaeger.log("resultOfMasterSpan","here is master span")
    res.send({code: 200, msg: "success"});
});

Lookup Request Tracing

open url http://localhost:16686 , remember to build up the Jager Server locally first

Object Detail

Config

for detail, pls look up to Jaeger Client for Node

{
  serviceName: "string",           // required
  disable: "boolean",
  sampler: {
    type: "string",                // required
    param: "number",               // required
    hostPort: "string",
    host: "string",
    port: "number",
    refreshIntervalMs: "number"
  },
  reporter: {
    logSpans: "boolean",
    agentHost: "string",
    agentPort: "number",
    collectorEndpoint: "string",   // required
    username: "string",
    password: "string",
    flushIntervalMs: "number"
  },
  throttler: {
    host: "string",
    port: "number",
    refreshIntervalMs: "number"
  }
}

options

for detail, pls look up to Jaeger Client for Node

{
    contextKey: "string",
    baggagePrefix: "string",
    metrics: "object", // a metrics
    logger: "object",  // a logger
    tags: "object",    // set of key-value pairs which will be set as process-level tags on the Tracer itself.
    traceId128bit: "boolean",
    shareRpcSpan: "boolean",
    debugThrottler: "boolean",
    excludePath:"array"  // array of parttern for excluding record the access
}

jaeger

jaeger object will bind in req when you do "app.use(jaeger(config,options))"

{
  log           : function(name,content)    // write the log to master span
  setTag        : function(name,value)      // setup tag to master span
  setTracingTag : function(name,value)      // setup tag to master span and children span 
  addTags       : function({k1:v1,k2:v2})   // setup mutiple tags to master span
  createSpan    : function(name)            // create a new span un der master span
  tags          : object                    // all defined tags of opentracing which can be used
  axios         : function(url,options)     // using it to remote call service if not it will be broken the tracing to next service
}

log

req.jaeger.log("info","..........")

setTag

const jaeger = req.jaeger
const tags = jaeger
// using defined tags by opentracing
jaeger.setTag(tags.ERROR,true)
// using your customize tag
jaeger.setTag("warning",true)

setTracingTag

const jaeger = req.jaeger
const tags = jaeger
jaeger.setTracingTag("waybill","wb-123456")

addTags

const jaeger = req.jaeger
const tags = jaeger
// add mutiple tag one time
jaeger.addTags({"error":true,"info":true})

createSpan

const span = jaeger.createSpan("subSpanName")   // create a sub span under master span
// you also can call method of span
span.log("info","info......")
span.setTag("info",true)
// remember to call finish() if not there is no record send to jaeger
span.finish();

tags

predefined tag, some come from OpenTracing project

axios

jaeger.axios wrap axios with tracing header, for usage detail pls look up to axios

license

MIT