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Note: This gem is still work in progress. It is not yet usable and does not support any end-to-end logging. The good news is that we are working on that :)

Rackstash is a Logger replacement for Ruby applications to allow flexible structured logging from request-based Ruby applications based on e.g Rack, Rails or similar frameworks. It works best with a log receiver like Logstash or Graylog.

Rackstash aims to provide a simple and clearly understood interface without too much magic. Being an infrastructure component of other apps, Rackstash aims to be extensible and adaptable towards novel use-cases.

This is the framework-agnostic base package with only minimal dependencies. There are several packages for framework-specifc integrations. If you use those, check out these gems:

Framework Gem
Ruby on Rails rackstash-rails
Hanami rackstash-hanami

Table of Contents

Why Rackstash


Add this line to your application's Gemfile:

gem 'rackstash'

And then execute:

$ bundle

Or install it yourself as:

$ gem install rackstash



require 'rackstash'

# Create a new logger which writes its logs to the log/application.log file
# The logger will write logs in Logstash's JSON format
logger = Rackstash::Logger.new('log/application.log')

# With this buffer, you can log single messages to the logfile, one after
# another. This works similar to a plain old Ruby logger. We support all
# methods you'd expect from a logger.
logger.info 'Hello World'

# You can create a new buffer using the with_buffer method. All log messages
# you send within the block will be appended to the buffer and will be flushed
# as a single log event only when you leave the block again.
# On each buffer, you can set (nested) fields and tags. These will be included
# in the log event written to the log file.
logger.with_buffer do
  logger.tag 'my_application'
  logger['server'] = Socket.gethostname

  logger.debug 'Starting request...'
  logger.info  'Performing some work...'
  logger.debug 'Done'

With the default JSON codec (you can chose another, see below) the emitted log events from the example above will look like this:

{"@version":"1","@timestamp":"2016-12-07T13:37:13.370Z","message":"Hello World","tags":[]}
{"server":"www.example.com","@version":"1","@timestamp":"2016-12-07T13:37:13.420Z","message":"Starting request...\nPerforming some work...\nDone","tags":["my_application"]}

As you can see, we have written only two log events to our log file. The second event contains all three logged messages in the "message" field.


After checking out the repo, run bin/setup to install dependencies. Then, run rake spec to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.


Bug reports and pull requests are welcome on GitHub at https://github.com/meineerde/rackstash. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the Contributor Covenant code of conduct.


The gem is available as open source under the terms of the MIT License.