class Logging::Layouts::Parseable

This layout will produce parseable log output in either JSON or YAML format. This makes it much easier for machines to parse log files and perform analysis on those logs.

The information about the log event can be configured when the layout is created. Any or all of the following labels can be set as the items to log:

'logger'     Used to output the name of the logger that generated the
             log event.
'timestamp'  Used to output the timestamp of the log event.
'level'      Used to output the level of the log event.
'message'    Used to output the application supplied message
             associated with the log event.
'file'       Used to output the file name where the logging request
             was issued.
'line'       Used to output the line number where the logging request
             was issued.
'method'     Used to output the method name where the logging request
             was issued.
'hostname'   Used to output the hostname
'pid'        Used to output the process ID of the currently running
             program.
'millis'     Used to output the number of milliseconds elapsed from
             the construction of the Layout until creation of the log
             event.
'thread_id'  Used to output the object ID of the thread that generated
             the log event.
'thread'     Used to output the name of the thread that generated the
             log event. Name can be specified using Thread.current[:name]
             notation. Output empty string if name not specified. This
             option helps to create more human readable output for
             multithread application logs.

These items are supplied to the layout as an array of strings. The items 'file', 'line', and 'method' will only work if the Logger generating the events is configured to generate tracing information. If this is not the case these fields will always be empty.

When configured to output log events in YAML format, each log message will be formatted as a hash in it's own YAML document. The hash keys are the name of the item, and the value is what you would expect it to be. Therefore, for the default set of times log message would appear as follows:

---
timestamp: 2009-04-17T16:15:42
level: INFO
logger: Foo::Bar
message: this is a log message
---
timestamp: 2009-04-17T16:15:43
level: ERROR
logger: Foo
message: <RuntimeError> Oooops!!

The output order of the fields is not guaranteed to be the same as the order specified in the items list. This is because Ruby hashes are not ordered by default (unless you're running this in Ruby 1.9).

When configured to output log events in JSON format, each log message will be formatted as an object (in the JSON sense of the word) on it's own line in the log output. Therefore, to parse the output you must read it line by line and parse the individual objects. Taking the same example above the JSON output would be:

{"timestamp":"2009-04-17T16:15:42","level":"INFO","logger":"Foo::Bar","message":"this is a log message"}
{"timestamp":"2009-04-17T16:15:43","level":"ERROR","logger":"Foo","message":"<RuntimeError> Oooops!!"}

The output order of the fields is guaranteed to be the same as the order specified in the items list.

Attributes

items[R]

Public Class Methods

json( opts ) click to toggle source

Create a new Parseable layout that outputs log events using JSON style formatting. See the initializer documentation for available options.

# File lib/logging/layouts/parseable.rb, line 159
def self.json( opts = {} )
  opts[:style] = 'json'
  new(opts)
end
new( opts ) click to toggle source

Creates a new Parseable layout using the following options:

:style      => :json or :yaml
:items      => %w[timestamp level logger message]
:utc_offset =>  "-06:00" or -21600 or "UTC"
Calls superclass method Logging::Layout.new
# File lib/logging/layouts/parseable.rb, line 184
def initialize( opts = {} )
  super
  @created_at = Time.now
  @style = opts.fetch(:style, 'json').to_s.intern
  self.items = opts.fetch(:items, %w[timestamp level logger message])
end
yaml( opts ) click to toggle source

Create a new Parseable layout that outputs log events using YAML style formatting. See the initializer documentation for available options.

# File lib/logging/layouts/parseable.rb, line 170
def self.yaml( opts = {} )
  opts[:style] = 'yaml'
  new(opts)
end

Public Instance Methods

format_cause(e) click to toggle source

Internal: Format any nested exceptions found in the given exception `e` while respecting the maximum `cause_depth`.

e - Exception to format

Returns the cause formatted as a Hash

# File lib/logging/layouts/parseable.rb, line 244
def format_cause(e)
  rv = curr = {}
  prev = nil

  cause_depth.times do
    break unless e.respond_to?(:cause) && e.cause

    cause = e.cause
    curr[:class]     = cause.class.name
    curr[:message]   = cause.message
    curr[:backtrace] = format_cause_backtrace(e, cause) if backtrace? && cause.backtrace

    prev[:cause] = curr unless prev.nil?
    prev, curr = curr, {}

    e = cause
  end

  if e.respond_to?(:cause) && e.cause
    prev[:cause] = {message: "Further #cause backtraces were omitted"}
  end

  rv
end
format_obj( obj ) click to toggle source

Public: Take a given object and convert it into a format suitable for inclusion as a log message. The conversion allows the object to be more easily expressed in YAML or JSON form.

If the object is an Exception, then this method will return a Hash containing the exception class name, message, and backtrace (if any).

obj - The Object to format

Returns the formatted Object.

# File lib/logging/layouts/parseable.rb, line 219
def format_obj( obj )
  case obj
  when Exception
    hash = {
      :class   => obj.class.name,
      :message => obj.message
    }
    hash[:backtrace] = obj.backtrace if backtrace? && obj.backtrace

    cause = format_cause(obj)
    hash[:cause] = cause unless cause.empty?
    hash
  when Time
    iso8601_format(obj)
  else
    obj
  end
end
items = %w[timestamp level logger message] click to toggle source

Set the log event items that will be formatted by this layout. These items, and only these items, will appear in the log output.

# File lib/logging/layouts/parseable.rb, line 199
def items=( ary )
  @items = Array(ary).map {|name| name.to_s.downcase}
  valid = DIRECTIVE_TABLE.keys
  @items.each do |name|
    raise ArgumentError, "unknown item - #{name.inspect}" unless valid.include? name
  end
  create_format_method
end

Private Instance Methods

create_format_method() click to toggle source

Call the appropriate class level create format method based on the style of this parseable layout.

# File lib/logging/layouts/parseable.rb, line 274
def create_format_method
  case @style
  when :json; Parseable.create_json_format_method(self)
  when :yaml; Parseable.create_yaml_format_method(self)
  else raise ArgumentError, "unknown format style '#@style'" end
end
iso8601_format( time ) click to toggle source

Convert the given `time` into an ISO8601 formatted time string.

# File lib/logging/layouts/parseable.rb, line 283
def iso8601_format( time )
  value = apply_utc_offset(time)

  str = value.strftime('%Y-%m-%dT%H:%M:%S')
  str << ('.%06d' % value.usec)

  offset = value.gmt_offset.abs
  return str << 'Z' if offset == 0

  offset = sprintf('%02d:%02d', offset / 3600, offset % 3600 / 60)
  return str << (value.gmt_offset < 0 ? '-' : '+') << offset
end