Class: RightSupport::Log::Syslog::Remote

Inherits:
Object
  • Object
show all
Defined in:
lib/right_support/log/syslog/remote.rb

Overview

partially implements the Syslog interface for a remote syslog connection. the Syslog.open method is restricted to only using the ‘/dev/log’ socket (or darwin equivalent).

Defined Under Namespace

Modules: Severity Classes: RemoteSyslogError

Instance Method Summary collapse

Constructor Details

#initialize(uri, program_name, facility, options = {}) ⇒ Remote

Returns a new instance of Remote.



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# File 'lib/right_support/log/syslog/remote.rb', line 56

def initialize(uri, program_name, facility, options = {})
  @uri = ::URI.parse(uri.to_s)
  @program_name = program_name
  @facility = facility
  @identity = "#{program_name}[#{$$}]"
  @hostname = ::Socket.gethostname.split('.').first
  @mutex = ::Mutex.new
  @socket = nil
  @error_handler = options[:error_handler]
  @error_mode = false
end

Instance Method Details

#alert(message) ⇒ Object 



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# File 'lib/right_support/log/syslog/remote.rb', line 125

def alert(message)
  log(@facility, Severity::ALERT, message)
end

#close ⇒ Object 



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# File 'lib/right_support/log/syslog/remote.rb', line 111

def close
  if @socket && !@socket.closed?
    @socket.close
  end
rescue => e
  STDERR.puts("Failed to close syslog socket: #{e.message}")
ensure
  @socket = nil
end

#connect ⇒ Object 



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# File 'lib/right_support/log/syslog/remote.rb', line 68

def connect
  close if @socket
  opener = nil
  case @uri.scheme
  when 'tcp'
    opener = lambda do
      ::TCPSocket.new(@uri.host, @uri.port)
    end
  when 'udp'
    opener = lambda do
      s = ::UDPSocket.new
      s.connect(@uri.host, @uri.port)
      s
    end
  else
    raise RemoteSyslogError, "Unxpected URI scheme: #{@uri.scheme}"
  end

  # backoff/retry connection. each log call will attempt to reconnect on
  # write failure but only the first will backoff/retry the connection.
  # the issue is to try and keep the service running and logging while
  # syslog is being restarted for routine maintainance. if syslog is offline
  # indefinitely then the app must continue without slowing. the caller can
  # provide an error_handler to perform graceful shutdown, etc.
  sleeper = 1
  attempts = 0
  begin
    @socket = opener.call
  rescue => e
    # do not repeat backoff/retry when already in error mode.
    raise if @error_mode
    attempts += 1
    if attempts <= 6   # about one minute
      STDERR.puts("Sleeping #{sleeper}s due to failure to (re)connect to syslog: #{e.message}\n")
      sleep(sleeper)
      sleeper *= 2
      retry
    else
      raise
    end
  end
end

#crit(message) ⇒ Object 



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# File 'lib/right_support/log/syslog/remote.rb', line 129

def crit(message)
  log(@facility, Severity::CRIT, message)
end

#debug(message) ⇒ Object 



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# File 'lib/right_support/log/syslog/remote.rb', line 149

def debug(message)
  log(@facility, Severity::DEBUG, message)
end

#emerg(message) ⇒ Object 



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# File 'lib/right_support/log/syslog/remote.rb', line 121

def emerg(message)
  log(@facility, Severity::EMERG, message)
end

#err(message) ⇒ Object 



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# File 'lib/right_support/log/syslog/remote.rb', line 133

def err(message)
  log(@facility, Severity::ERR, message)
end

#info(message) ⇒ Object 



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# File 'lib/right_support/log/syslog/remote.rb', line 145

def info(message)
  log(@facility, Severity::INFO, message)
end

#log(facility, severity, message) ⇒ Object 



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# File 'lib/right_support/log/syslog/remote.rb', line 153

def log(facility, severity, message)
  protocol_message = "<#{(facility & 0xf8) | (severity & 0x07)}> "\
    "#{::Time.now.strftime('%b %d %H:%M:%S')} " \
    "#{@hostname} " \
    "#{@identity}" \
    ": " \
    "#{message.gsub("\n", '#012')}\n"
  @mutex.synchronize do
    last_error = nil
    begin
      @socket.write(protocol_message)
    rescue => e
      if reconnect
        begin
          @socket.write(protocol_message)
        rescue => e
          last_error = e
        end
      else
        last_error = e
      end
    end
    if last_error
      # we are only here if reconnection attempts have timed out at least
      # once. the timeout is skipped when we are already in error mode.
      if @error_mode
        # no need to repeat the warning or invoke callback for each
        # failure to write.
        ::STDERR.puts(protocol_message)
      else
        @error_mode = true
        msg = <<EOF
WARNING: Failed writing to syslog: #{last_error.message}
Dumping raw messages to stderr until rsyslog connection is restored.
EOF
        ::STDERR.puts(msg)
        ::STDERR.puts(protocol_message)

        # the caller may want to gracefully shutdown, etc. graceful shutdown
        # will trigger alerts whereas silently ignoring failure to write to
        # syslog can lead to other problems.
        @error_handler.call(last_error) if @error_handler
      end
    else
      @error_mode = false
    end
  end
  true
end

#notice(message) ⇒ Object 



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# File 'lib/right_support/log/syslog/remote.rb', line 141

def notice(message)
  log(@facility, Severity::NOTICE, message)
end

#warning(message) ⇒ Object 



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# File 'lib/right_support/log/syslog/remote.rb', line 137

def warning(message)
  log(@facility, Severity::WARNING, message)
end