Logging in Sinatra?

I'm having trouble figuring out how to log messages with Sinatra. I'm not looking to log requests, but rather custom messages at certain points in my app. For example, when fetching a URL I would like to log "Fetching #{url}".

Here's what I'd like:

• The ability to specify log levels (ex: logger.info("Fetching #{url}"))
• In development and testing environments, the messages would be written to the console.
• In production, only write out messages matching the current log level.

I'm guessing this can easily be done in config.ru, but I'm not 100% sure which setting I want to enable, and if I have to manually create a Logger object myself (and furthermore, which class of Logger to use: Logger, Rack::Logger, or Rack::CommonLogger).

(I know there are similar questions on StackOverflow, but none seem to directly answer my question. If you can point me to an existing question, I will mark this one as a duplicate).

Solution 1:

Sinatra 1.3 will ship with such a logger object, exactly usable as above. You can use edge Sinatra as described in "The Bleeding Edge". Won't be that long until we'll release 1.3, I guess.

To use it with Sinatra 1.2, do something like this:

require 'sinatra'
use Rack::Logger

helpers do
  def logger
    request.logger
  end
end

Solution 2:

I personally log in Sinatra via:

require 'sinatra'
require 'sequel'
require 'logger'
class MyApp < Sinatra::Application
  configure :production do
    set :haml, { :ugly=>true }
    set :clean_trace, true

    Dir.mkdir('logs') unless File.exist?('logs')

    $logger = Logger.new('logs/common.log','weekly')
    $logger.level = Logger::WARN

    # Spit stdout and stderr to a file during production
    # in case something goes wrong
    $stdout.reopen("logs/output.log", "w")
    $stdout.sync = true
    $stderr.reopen($stdout)
  end

  configure :development do
    $logger = Logger.new(STDOUT)
  end
end

# Log all DB commands that take more than 0.2s
DB = Sequel.postgres 'mydb', user:'dbuser', password:'dbpass', host:'localhost'
DB << "SET CLIENT_ENCODING TO 'UTF8';"
DB.loggers << $logger if $logger
DB.log_warn_duration = 0.2

Solution 3:

If you are using something like unicorn logging or other middleware that tails IO streams, you can easily set up a logger to STDOUT or STDERR

# unicorn.rb
stderr_path "#{app_root}/shared/log/unicorn.stderr.log"
stdout_path "#{app_root}/shared/log/unicorn.stdout.log"

# sinatra_app.rb
set :logger, Logger.new(STDOUT) # STDOUT & STDERR is captured by unicorn
logger.info('some info') # also accessible as App.settings.logger

this allows you to intercept messages at application scope, rather than just having access to logger as request helper