Class: Logging::Layouts::Parseable

### Home Classes Methods

### In Files

- lib/logging/layouts/parseable.rb

### Parent

Logging::Layout

### Methods

- ::json
- ::new
- ::yaml
- #format_obj
- #items=

### Files

- History.txt
- README.rdoc

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# 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.
    '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 156
    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]

    # File lib/logging/layouts/parseable.rb, line 180
    def initialize( opts = {} )
      super
      @created_at = Time.now
      @style = opts.getopt(:style, 'json').to_s.intern
      self.items = opts.getopt(:items, ]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 167
    def self.yaml( opts = {} )
      opts[:style] = 'yaml'
      new(opts)
    end

### Public Instance Methods

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 215
    def format_obj( obj )
      case obj
      when Exception
        h = { :class   => obj.class.name,
              :message => obj.message }
        h[:backtrace] = obj.backtrace if @backtrace && !obj.backtrace.nil?
        h
      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 195
    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

[Validate]

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