trace-json

Distributed tracing library. Traces are really just a specialized form of log calls, therefore this module utilizes Automattic/log-json under the hood.

About

Traces works by collecting "cycles", which consist of one or more trace calls enabling you to report on the durations of any given subset of a cycle. For example an image upload "cycle" may look something like the following, where each aspect of this request/response cycled may be "traced" for inspection. Because of this association each Cycle must have its own "id", which may be unique identifier, allowing traces cross-process.

var http = require('http');
var cycle = require('trace-json');
 
var id = 0;
http.createServer(function(){
  var trace = cycle('upload', id++);
 
  // request comes in, start streaming data
  trace.start('request');
  trace.start('upload');
 
  // upload complete
  trace.end('upload');
 
  // resize
  trace.start('resize');
 
  // resize complete
  trace.end('resize');
 
  // respond
  trace.end('request');
})

Enabling probes

To enable a cycle you may use the TRACE environment variable. For example to enable all probes simply use TRACE="*", to enable only chat related cycles use TRACE=chat, for several use spaces or commas TRACE="chat request", TRACE=chat,request. You may also use wildcards such as TRACE=chat:*, and negation via TRACE="* -chat" to say "everything except chat".

API

Cycle(id, name)

Initialize a new Tracer with the given id and name.

Cycle#start(type:String, [date]:Number|Date)

Trace start of type with optional date.

Cycle#end(type:String, [date]:Number|Date)

Trace end of type with optional date.