tunyan

A command-line tool to transform bunyan logs (or any ndjson stream).

This tool is heavily inspired by @mpareja's comment here.

Install

  npm install -g tunyan

Usage

  node server.js | tunyan <formatterFilePath> | bunyan

Input

formatterFilePath - formatter is simply a nodejs module which returns a function of the following format:

  function formatter(logObj) {
    // logObj is the bunyan (or any json parsed) object
    ...
    // transform logObj
    ...
    return logObj;
  }
    
  module.exports = formatter;

The real power of tunyan is when you can save anything you like in your logs and then transform them for custom viewing

Typical Use Case

We are using tunyan mainly to suppress certain fields and customize msg in bunyan logs for viewing.

Let's say your logs look like this:

  node test.js
  {"name":"myApp","hostname":"myHost","pid":7760,"level":30,"type":"rest","url":"http://blah.com/1b95f96c-6ba0-332a-b9d1-ab059d0a6d0f.json","method":"GET","duration":1439,"msg":"some rest message","someField":"not for viewing, but can be used for some analysis","time":"2016-05-12T09:49:51.444Z","v":0}
  {"name":"myApp","hostname":"myHost","pid":7760,"level":30,"type":"done","url":"/1b95f96c-6ba0-332a-b9d1-ab059d0a6d0f/address","method":"GET","service":"address service","duration":1540,"msg":"some done message","someField":"not for viewing, but can be used for some analysis","time":"2016-05-12T09:49:52.444Z","v":0}
  {"name":"myApp","hostname":"myHost","pid":7760,"level":30,"type":"rest","url":"http://blah.com/all.json","method":"GET","duration":1890,"msg":"some rest message","someField":"not for viewing, but can be used for some analysis","time":"2016-05-12T09:49:55.444Z","v":0}
 

With bunyan CLI (with some colors of-course)

  node test.js | bunyan -o short
  09:49:51.444Z  INFO myApp: some rest message (type=rest, method=GET, duration=1439, someField="not for viewing, but can be used for some analysis")
    url: http://blah.com/1b95f96c-6ba0-332a-b9d1-ab059d0a6d0f.json
  09:49:52.444Z  INFO myApp: some done message (type=done, url=/1b95f96c-6ba0-332a-b9d1-ab059d0a6d0f/address, method=GET, service="address service", duration=1540, someField="not for viewing, but can be used for some analysis")
  09:49:55.444Z  INFO myApp: some rest message (type=rest, url=http://blah.com/all.json, method=GET, duration=1890, someField="not for viewing, but can be used for some analysis")

Now lets have a tunyan formatter (formatter.js)

  function formatter(logObject) {
    switch (logObject.type) {
        case 'rest':
            logObject.msg += ' : ' + logObject.method + ' ' + logObject.url + ' in ' + logObject.duration + 'ms';
            delete logObject.url;
            delete logObject.method;
            delete logObject.duration;
            break;
        case 'done':
            logObject.msg = logObject.service + ' : ' + logObject.msg;
            // we donot want to view these fields
            delete logObject.url;
            delete logObject.method;
            delete logObject.duration;
            break;
    }
 
    // we also want to suppress this field
    delete logObject.someField;
    return logObject;
  }
 
  module.exports = formatter;

Your log with tunyan

  node test.js | tunyan formatter.js 
  {"name":"myApp","hostname":"myHost","pid":7760,"level":30,"type":"rest","msg":"some rest message : GET http://blah.com/1b95f96c-6ba0-332a-b9d1-ab059d0a6d0f.json in 1439ms","time":"2016-05-12T09:49:51.444Z","v":0}
  {"name":"myApp","hostname":"myHost","pid":7760,"level":30,"type":"done","service":"address service","msg":"address service : some done message","time":"2016-05-12T09:49:52.444Z","v":0}
  {"name":"myApp","hostname":"myHost","pid":7760,"level":30,"type":"rest","msg":"some rest message : GET http://blah.com/all.json in 1890ms","time":"2016-05-12T09:49:55.444Z","v":0}

Now with bunyan CLI

  09:49:51.444Z  INFO myApp: some rest message : GET http://blah.com/1b95f86c-6ba0-332a-b9d1-ab059d0a6d0f.json in 1439ms (type=rest)
  09:49:52.444Z  INFO myApp: address service : some done message (type=done, service="address service")
  09:49:55.444Z  INFO myApp: some rest message : GET http://blah.com/all.json in 1890ms (type=rest)

And you can have any number of formatters as you like to see different kinds of outputs :)