LoreKeeper contains a highly optimized JSON logger. It outputs messages as JSON and let the users to add their own customized fields. When used without extra fields it outputs 20% faster than the standard Logger for messages not longer than one line of text.

Add this line to your application's Gemfile:

gem 'lorekeeper', '~> 1.7'

And then execute:

bundle

LoreKeeper::JSONLogger API is compatible with the stdlib's Logger's.

logger.error("This is a message")

Will output:

{
  "message": "This is a message",
  "timestamp": "1970-01-01T00:00:00.000+0100",
  "level": "debug"
}

Timestamps use ISO8601. Messages are JSON escaped so the total result is JSON parseable.

Keys can be added to the output at any moment. These keys will be output in each message till they are removed again. If you want to output keys in only one message use the *_with_data method instead.

Keys can be added using the add_fields method which accepts a hash:

logger.add_fields("role" => "backend")
logger.error("This is a message")
logger.warn("This is another message")

Will output:

{
  "message": "This is a message",
  "timestamp": "1970-01-01T00:00:00.000+0100",
  "level": "error",
  "role": "backend"
}
{
  "message": "This is another message",
  "timestamp": "1970-01-01T00:00:00.000+0100",
  "level": "warning",
  "role": "backend"
}

Because of speed purposes the JSON dumping is done as simply as possible. If you provide a hash of keys like:

{ key: 'value' }

The output will include:

{ ":key": "value" }

All methods (info, debug, etc.) have a *_with_data equivalent: info_with_data, debug_with_data, etc. These methods accept and extra hash to add it to the JSON.

logger.error_with_data('message', { data1: 'Extra data', data2: 'Extra data2' })

Will output:

{
  "message": "This is a message",
  "timestamp": "1970-01-01T00:00:00.000+0100",
  "level": "debug",
  "data": {
    "data1": "Extra data",
    "data2": "Extra data2"
  }
}

There is a method to help you log exceptions in an standard way.

rescue => e
  logger.exception(e)
end

Will output:

{
  "message": "#{e.message}",
  "timestamp": "1970-01-01T00:00:00.000+0100",
  "level": "error",
  "exception": "<exception name>",
  "stack": [
    "<stacktraceline1>",
    "<stacktraceline2>"
  ]
}

This method also accepts a custom message, data and log level.

rescue => e
  logger.exception(e, "custom msg!", { some: { data: 123 } }, :warn)
end

Will output:

{
  "message": "custom msg!",
  "timestamp": "1970-01-01T00:00:00.000+0100",
  "level": "warning",
  "data": {
    ":some": {
      ":data": 123
    }
  },
  "exception": "<exception name>",
  "stack": [
    "<stacktraceline1>",
    "<stacktraceline2>"
  ]
}

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