Class: Safis::Logging::SimpleFormatter

Inherits:
Object
  • Object
show all
Defined in:
lib/safis/logging/simple_formatter.rb

Overview

A simple log formatter.

This formatter generates logging output in the following format:

SEVERITY: [component HH:MM:SS] Log message [ISO-8601 Datetime]

If the log event had details associated with it, the details value is inspected and printed to the following line. Exceptions are logged with their full backtrace.

A Few Examples

Simple log event

WARN: [Object 19:57:24] The world shall be ours! ...in due time. [2009-07-01T19:57:24.818687-07:00]

Log event with details

INFO: [Villany::DoomLaser 04:32:27] Doom laser locked on target. [2009-07-02T04:32:27.775913-07:00]
  #<Villany::DoomLaser:0x13ee44 @power_level=11, @target=[40.689606, -74.044901]>

Log event with an exception as details

FATAL: [Villany::SharkTankTrapDoor 20:24:38] The trap door failed to open. Execute the nearest henchman immediately! [2009-07-01T20:24:38.747175-07:00]
  TrapDoorFailure: The magma vents are blocked.
    /villany/power_source/geothermal.rb:27:in `reroute_magma_flow'
    /villany/power_source/geothermal.rb:53:in `check_power_levels'
    ...

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(output = STDOUT) ⇒ SimpleFormatter

Creates a new SimpleFormatter.

Parameters:

  • output (optional, #write) (defaults to: STDOUT) —

    An IO-like object to write our formatted logging output to.



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# File 'lib/safis/logging/simple_formatter.rb', line 49

def initialize(output = STDOUT)
  @output = output
end

Class Method Details

.format_event(event) ⇒ String

Formats an event.

An event is an array with values in the following order:

  • severity

  • component name

  • timestamp

  • message

  • event details (optional - usually an exception)

Parameters:

  • event (Array) —

    The event to log.

Returns:

  • (String) —

    The formatted event.



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# File 'lib/safis/logging/simple_formatter.rb', line 115

def self.format_event(event)
  result = ''
  
  severity   = event[0].to_s.upcase
  component  = event[1]
  short_time = event[2].strftime('%H:%M:%S')
  iso_time   = event[2].iso8601
  message    = event[3]
  details    = event[4]
  
  result << "#{severity}: [#{component} #{short_time}] #{message} [#{iso_time}]\n"
  
  if ( not details.nil? ) then
    # Does it look like an exception?
    if ( details.respond_to? :backtrace ) then
      result << '  ' + details.message + "\n"
      
      # and the backtrace
      details.backtrace.each do |line|
        result << '    ' + line + "\n"
      end
      
    # Nope, just inspect it
    else
      result << '  ' + details.inspect + "\n"
    end
  end
  
  return result
end

Instance Method Details

#log_event(event, filter = true) ⇒ SimpleFormatter

Formats and outputs an event.

An event is an array with values in the following order:

  • severity

  • component name

  • timestamp

  • message

  • event details (optional - usually an exception)

Parameters:

  • event (Array) —

    The event to log.

  • filter (Boolean) (defaults to: true) —

    This is ignored by SimpleFormatter. It does not filter events.

Returns:



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# File 'lib/safis/logging/simple_formatter.rb', line 66

def log_event(event, filter = true)
  begin
    formatted_event = self.class.format_event(event)
    
  # The logging facilities shouldn't generate exceptions themselves if we can help it.
  rescue Exception => err
    formatted_event  = "We failed to format a log event!  Event details:\n"
    formatted_event << event.inspect + "\n"
    formatted_event << "Exception: #{err.message}\n"
    err.backtrace.each do |line|
      formatted_event << line + "\n"
    end
  end
  
  # Write the entry as a single transaction
  begin
    @output.write(formatted_event)
    
  rescue Exception => err
    # Generate an event for this exception (SPAMMY!)
    write_failure = self.class.format_event([
      :error,
      self.class.name,
      Time.now,
      "Unable to write a formatted log event to #{@output.inspect}!",
      err
    ])
    STDERR.write(write_failure)
    
    # Write the original error
    STDOUT.write(result)
  end
  
  # For those who love to chain
  self
end