Rack::JsonLogs

Rack::JsonLogs is a gem that helps log sanely in production.

Ever request will log a JSON object to the real stdout, containing the following (note: whitespace added here for clarity, in production it would only be a single line, for easier processig through tools like grep):

{
   "request": "GET /hello",
   "status": 500,
   "time": 1379703636,
   "duration": 0.05,
   "from": "server-1",
   "stdout": "This contains the STDOUT\nLines are separated by \\n",
   "stderr": "This contains the STDERR\nLines are separated by \\n",
   "events": [
      {
         "type": "event",
         "value": "something awesome happened",
         "time": 0.3
      }
   ],
   "exception": {
      "message": "Throwing an exception on purpose.",
      "backtrace": [
         "config.ru:9:in `block (2 levels) in <main>'",
         ".../rack-json-logs/lib/rack-json-logs.rb:23:in `call'",
         ".../rack-json-logs/lib/rack-json-logs.rb:23:in `call'",
         "etc... you get the idea"
      ]
   }
}

Rack::JsonLogs comes with a command-line tool to which you can pipe the log files, which will be pretty-printed for legibility and in color:

$ tail -F my.log | json-log-pp

Request: GET /hello
From: server-1

stdout:
hello world

stderr:
bye world

Exception: exception on purpose
  config.ru:12:in `block (2 levels) in <main>'
  /Users/kenneth/Dropbox/dev/azure/rack-json-logs/lib/rack-json-logs.rb:24:in `call'
  /Users/kenneth/Dropbox/dev/azure/rack-json-logs/lib/rack-json-logs.rb:24:in `call'
  /Users/kenneth/.rvm/gems/ruby-1.9.3-p327/gems/thin-1.5.0/lib/thin/connection.rb:81:in `block in pre_process'
  /Users/kenneth/.rvm/gems/ruby-1.9.3-p327/gems/thin-1.5.0/lib/thin/connection.rb:79:in `catch'
  /Users/kenneth/.rvm/gems/ruby-1.9.3-p327/gems/thin-1.5.0/lib/thin/connection.rb:79:in `pre_process'
  /Users/kenneth/.rvm/gems/ruby-1.9.3-p327/gems/thin-1.5.0/lib/thin/connection.rb:54:in `process'
  /Users/kenneth/.rvm/gems/ruby-1.9.3-p327/gems/thin-1.5.0/lib/thin/connection.rb:39:in `receive_data'
  /Users/kenneth/.rvm/gems/ruby-1.9.3-p327/gems/eventmachine-1.0.0/lib/eventmachine.rb:187:in `run_machine'
  /Users/kenneth/.rvm/gems/ruby-1.9.3-p327/gems/eventmachine-1.0.0/lib/eventmachine.rb:187:in `run'
  /Users/kenneth/.rvm/gems/ruby-1.9.3-p327/gems/thin-1.5.0/lib/thin/backends/base.rb:63:in `start'
  /Users/kenneth/.rvm/gems/ruby-1.9.3-p327/gems/thin-1.5.0/lib/thin/server.rb:159:in `start'
  /Users/kenneth/.rvm/gems/ruby-1.9.3-p327/gems/thin-1.5.0/lib/thin/controllers/controller.rb:86:in `start'
  /Users/kenneth/.rvm/gems/ruby-1.9.3-p327/gems/thin-1.5.0/lib/thin/runner.rb:187:in `run_command'
  /Users/kenneth/.rvm/gems/ruby-1.9.3-p327/gems/thin-1.5.0/lib/thin/runner.rb:152:in `run!'
  /Users/kenneth/.rvm/gems/ruby-1.9.3-p327/gems/thin-1.5.0/bin/thin:6:in `<top (required)>'
  /Users/kenneth/.rvm/gems/ruby-1.9.3-p327/bin/thin:19:in `load'
  /Users/kenneth/.rvm/gems/ruby-1.9.3-p327/bin/thin:19:in `<main>'
  /Users/kenneth/.rvm/gems/ruby-1.9.3-p327/bin/ruby_noexec_wrapper:14:in `eval'
  /Users/kenneth/.rvm/gems/ruby-1.9.3-p327/bin/ruby_noexec_wrapper:14:in `<main>'


Request: GET /hello
From: server-2

stdout:
hello world

stderr:
bye world

Installation

Add this line to your application's Gemfile:

gem 'rack-json-logs'

And then execute:

$ bundle

Or install it yourself as:

$ gem install rack-json-logs

Usage

Using Rack::JsonLogs is easy, all you need to do is add it to your middleware stack:

use Rack::JsonLogs

Using the command line tool is also easy. Output can be configured, see:

$ json-log-pp -h    
Options:
                   --stdout, -o:   Print stdout.
                   --stderr, -e:   Print stderr.
          --from, --no-from, -f:   Print from. (Default: true)
                    --trace, -b:   Print full backtraces.
  --duration, --no-duration, -d:   Print request duration. (Default: true)
                   --events, -v:   Print events.
                     --help, -h:   Show this message

Changelog

1.1

New feature: can pretty print from middleware, for development usage.
Refactoring of binary pretty print code into library.

1.0

Production release. Deployed and used in a large-scale system.

Big feature: Event logging.
json-log-pp output can be configured with CLI options.
Log request duration.
Logs status codes.
Bug fixes.

0.0.1

Initial release.

Contributing

Fork it
Create your feature branch (git checkout -b my-new-feature)
Commit your changes (git commit -am 'Add some feature')
Push to the branch (git push origin my-new-feature)
Create new Pull Request