Logging in Sinatra? - ruby

Question

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).

Answer 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

Answer 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

Answer 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

Answer 4

Here's another solution:
module MySinatraAppLogger
extend ActiveSupport::Concern
class << self
def logger_instance
#logger_instance ||= ::Logger.new(log_file).tap do |logger|
::Logger.class_eval { alias :write :'<<' }
logger.level = ::Logger::INFO
end
end
def log_file
#log_file ||= File.new("#{MySinatraApp.settings.root}/log/#{MySinatraApp.settings.environment}.log", 'a+').tap do |log_file|
log_file.sync = true
end
end
end
included do
configure do
enable :logging
use Rack::CommonLogger, MySinatraAppLogger.logger_instance
end
before { env["rack.errors"] = MySinatraAppLogger.log_file }
end
def logger
MySinatraAppLogger.logger_instance
end
end
class MySinatraApp < Sinatra::Base
include MySinatraAppLogger
get '/' do
logger.info params.inspect
end
end
Of course, you can do it without ActiveSupport::Concern by putting the configure and before blocks straight into MySinatraApp, but what I like about this approach is that it's very clean--all logging configuration is totally abstracted out of the main app class.
It's also very easy to spot where you can change it. For instance, the SO asked about making it log to console in development. It's pretty obvious here that all you need to do is a little if-then logic in the log_file method.