logfmtr

The default ruby logger (require 'logger') outputs in this format:

I, [2015-07-01T11:47:45.157173 #29367]  INFO -- : some message here (StandardError)

This provides a replacement for the default Logger::Formatter class, and it formats logs in key=value format.

Logs a hash as:

{ one: 1, two: 2 } => one=1 two=2

Everything else as:

=> msg="your message here"

Usage

Example logging error

Errors have their own .to_s implementation.

require 'logger'
require 'logfmtr'

logger = Logger.new($stdout)
logger.formatter = Logfmtr::LogfmtLogger.new

begin
  raise StandardError.new('some output')
rescue => e
  logger.error e
end

# output
# level=ERROR datetime="2015-07-01 08:29:52" -0500 progname= msg="some output"

Example logging error with a custom datetime format

require 'logger'
require 'logfmtr'

logger = Logger.new($stdout)
logger.formatter = Logfmtr::LogfmtLogger.new("%Y-%m-%d %H:%M %Z")

begin
  raise StandardError.new('some output')
rescue => e
  logger.error e
end

# output
# level=ERROR datetime="2015-07-01 08:29 CDT" progname= msg="some output"

Example logging hash

It pulls out hash values into their own key=value pairs in logfmt.

require 'logger'
require 'logfmtr'

logger = Logger.new($stdout)
logger.formatter = Logfmtr::LogfmtLogger.new

logger.info({ one: 1, two: 2 })

# output
# level=INFO datetime="2015-07-01 08:29 CDT" progname= one=1 two=2

Note about datetime_format

The default datetime_format in Logger::Formatter appears to be "%Y-%m-%d %H:%M:%S %z". When you set your logger.datetime_format=, it does not get used by the formatter class. Logger::Formatter appears to have its own default. This gem makes that explicit.