An EventMachine Syslog Protocol

em_syslog2.rb

# this is a configurable version of an EventMachine syslogger
# It was build to replace https://github.com/melito/em-syslog
#
# You can instantiate many of them (no global variables) as
# well as configure the facility. It also quacks like a ruby
# logger so it can be interchanged with a ruby logger.
#
# Example:
#
#     # 11 is the facility code for an FTP daemon
#     # 514 is the default UDP port for SYSLOG
#     syslog = EM::Protocols::Syslog2.connect('localhost', 514, 11)
#     # later ...
#     syslog.info "Hello world"
#     syslog.error "Goodbye world :-("
#
# Quick note: on my system, syslog was not listening to UDP by
# default, I had to enable it in its config. Because it's UDP
# you won't get an error :-)
class EventMachine::Protocols::Syslog2 < EventMachine::Connection
  def self.connect(host, port, facility)
    # open a null socket for sending
    EM.open_datagram_socket('0.0.0.0', 0, self, facility, host, port)
  end

  attr_reader :facility, :host, :port

  # Initialize accepts the log `facility` as defined
  # by the rfc:
  #
  # Numerical             Facility
  #    Code
  #     0             kernel messages
  #     1             user-level messages
  #     2             mail system
  #     3             system daemons
  #     4             security/authorization messages
  #     5             messages generated internally by syslogd
  #     6             line printer subsystem
  #     7             network news subsystem
  #     8             UUCP subsystem
  #     9             clock daemon
  #    10             security/authorization messages
  #    11             FTP daemon
  #    12             NTP subsystem
  #    13             log audit
  #    14             log alert
  #    15             clock daemon (note 2)
  #    16             local use 0  (local0)
  #    17             local use 1  (local1)
  #    18             local use 2  (local2)
  #    19             local use 3  (local3)
  #    20             local use 4  (local4)
  #    21             local use 5  (local5)
  #    22             local use 6  (local6)
  #    23             local use 7  (local7)
  #
  # Also sets the host and port to send UDP datagrams to.
  def initialize(facility, host, port)
    @facility = facility
    @host = host
    @port = port
  end

  # Error helper to behave like a ruby logger
  def error(message, time = Time.now) log(severity(:error),   message, time) end
  # Warn helper to behave like a ruby logger
  def warn (message, time = Time.now) log(severity(:warning), message, time) end
  # Info helper to behave like a ruby logger
  def info (message, time = Time.now) log(severity(:info),    message, time) end
  # Debug helper to behave like a ruby logger
  def debug(message, time = Time.now) log(severity(:debug),   message, time) end

  private

  # We don't use all of these, but if we wanted to they are here
  # From the RFC:
  #
  # Numerical         Severity
  #   Code
  #    0       Emergency: system is unusable
  #    1       Alert: action must be taken immediately
  #    2       Critical: critical conditions
  #    3       Error: error conditions
  #    4       Warning: warning conditions
  #    5       Notice: normal but significant condition
  #    6       Informational: informational messages
  #    7       Debug: debug-level messages
  def self.severity(sym)
    { :emergency => 0,
      :alert => 1,
      :critical => 2,
      :error => 3,
      :warning => 4,
      :notice => 5,
      :informational => 6,
      :info => 6,
      :debug => 7
    }[sym]
  end
  delegate :severity, :to => self

  # severity: integer indicating severity level (NOT a symbol)
  # message: message to log
  # time: time of the event to report
  #
  # ruby message encoding from: http://github.com/kpumuk/ruby_syslog    
  def log(severity, message, time)
    day = time.strftime('%b %d').sub(/0(\d)/, ' \\1')
    tag = "#{$0.split('/').last.split('.').first}[#{Process.pid}]"
    send_datagram "<#{facility * 8 + severity}>#{day} #{time.strftime('%T')} #{tag}: #{message}", host, port
  end
end

em_syslog2_test.rb

require 'test/test_helper'

class EM::SyslogTest < ActiveSupport::TestCase
  class FakeSyslog < EM::Connection
    attr_accessor :message
    def self.listen(host, port)
      EM::open_datagram_socket(host, port, self)
    end

    def receive_data(data)
      # <22>Dec 12 15:54:09 syslog_test[11792]: hello world
      data =~ /^<(\d+)>/
      level = $1.to_i
      data =~ / ([^:]+)$/
      msg = $1
      self.message = [level,msg]
      EM.stop
    end
  end

  [
    [:error, 19],
    [:warn,  20],
    [:info,  22],
    [:debug, 23]
  ].each do |level_name, level|
    test "log #{level_name} message" do
      host = "127.0.0.1"
      port = "1514"
      server = nil
      syslog = nil

      eventmachine do
        server = FakeSyslog.listen(host, port)
        syslog = EM::Protocols::Syslog2.connect(host, port, 2)
        syslog.send(level_name, "hello world")
      end

      assert_equal [level, "hello world"], server.message
    end
  end
end

also that magic "eventmachine" function is this:

  def eventmachine(timeout = 1)
    Timeout::timeout(timeout) do
      EM.run do
        EM.epoll
        yield
      end
    end
  end

Also nice for writing specs requiring EventMachine is the https://rubygems.org/gems/evented-spec gem

Except that's an rspec library and I use T::U and MiniTest :-(

An excellent point - stealing the API is also an option :)