logson

Simple middleware library to get the application logs (Express) and do whatever you want with them

Usage no npm install needed!

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  import logson from 'https://cdn.skypack.dev/logson';
</script>

README

logson

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Simple middleware library to get the application logs (Express) and do whatever you want with them

Install

With npm:

  gt; npm install --save logson

API

  var logson = require('logson');

logson(options|callback, [callback])

You can use it with options or without, in this case the first param will be the callback.

  var app = require('express')();
  var logson = require('logson');

  app.use(logson(function(log) {
    // Then you can use the log here
  }));

With options:

  var app = require('express')();
  var logson = require('logson');

  var options = {
    parent: 'parent'
  }

  app.use(logson(options, function(log) {
    // Then you can use the log here
  }))

By default the format is the following:

  { }

req._logson

When you use logson it declares an attribute to the req object with the name _logson. You can set whatever you want to this attribute that will be merged to the final log.

Options

format

You can specify different types of log format (the array represents all the keys of the log):

  • combined
  ['remoteAddr', 'date', 'method', 'url', 'httpVersion', 'status', 'contentLength', 'referrer', 'userAgent']
  • common
  [ 'remoteAddr', 'date', 'method', 'httpVersion', 'status', 'contentLength']
  • dev
  [ 'method', 'status', 'responseTime', 'contentLength']
  • short
  [ 'remoteAddr', 'url', 'httpVersion', 'method', 'responseTime', 'contentLength' ]
  • tiny
  [ 'method', 'url', 'status', 'responseTime', 'contentLength' ]

parent

This options encapsulates the log object:

  var logson = require('logson');

  var options = {
    parent: 'parent'
  };

  logson(options, funciton(log) {
    // The log object is { parent: log }
  })

extras

With this option you can add extra fields to the JSON log, when extras are defined you can have access to the req and res objects:

  var logson = require('logson');

  var options = {
    extras: function(req, res) {
      return {
        cookies: req.cookies
      }
    }
  };

  logson(options, funciton(log) {
    // The log object has the cookies field on it
  })

extras use a deepmerge methology so the object returned with it will be merged with the log.

Merge order

There are so many configurations that merge between them so the order is important, to no override fields.

The ored of this merge is the following: req._logson + format + parent + extras

Examples

A simple Use Case for logson is to save the log object to the DB, for example elastic:

  // Your elastic configuration
  var elastic = require('./elastic');
  var app = require('express')();

  app.use(logson(function(log) {
    elastic.create({
      index: 'index',
      type: 'type',
      body: log
    });
  })

If you want to save the cookies and wrap the log into a request name use the following:

  // All your app configuration
  var cookieParser = require('cookie-parser');

  app.use(cookieParser('pass'));

  var conf = {
    parent: 'request',
    extras: function(req, res) {
      return {
        request: {
          headers: {
            cookeis: req.signedCookies
          }
        }
      }
    }
  };

  app.use(conf, logson(function(log) {
    elastic.create({
      index: 'index',
      type: 'type',
      body: log
    });
  })

License

MIT