Class: MongoRecord::LogDevice

Inherits:
Object
  • Object
show all
Defined in:
lib/mongo_record/log_device.rb

Overview

A destination for Ruby’s built-in Logger class. It writes log messages to a Mongo database collection. Each item in the collection consists of two fields (besides the _id): time and msg. time is automatically generated when write is called.

If we are running outside of the cloud, all log messages are echoed to $stderr.

The collection is capped, which means after the limit is reached old records are deleted when new ones are inserted. See the new method and the Mongo documentation for details.

Example:

logger = Logger.new(MongoRecord::LogDevice('my_log_name'))

The database connection defaults to the global $db. You can set the connection using MongoRecord::LogDevice.connection= and read it with MongoRecord::LogDevice.connection.

# Set the connection to something besides $db
MongoRecord::LogDevice.connection = connect('my-database')

Constant Summary collapse

DEFAULT_CAP_SIZE = 
(10 * 1024 * 1024)
@@connection = 
nil

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(name, options = {}) ⇒ LogDevice

name is the name of the Mongo database collection that will hold all log messages. options is a hash that may have the following entries:

:size - Optional. The max size of the collection, in bytes. If it is nil or negative then DEFAULT_CAP_SIZE is used.

:max - Optional. Specifies the maximum number of log records, after which the oldest items are deleted as new ones are inserted.

:stderr - Optional. If not nil then all log messages will be copied to $stderr.

Note: a non-nil :max requires a :size value. The collection will never grow above :size. If you leave :size nil then it will be DEFAULT_CAP_SIZE.

Note: once a capped collection has been created, you can’t redefine the size or max falues for that collection. To do so, you must drop and recreate (or let a LogDevice object recreate) the collection.



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# File 'lib/mongo_record/log_device.rb', line 83

def initialize(name, options = {})
  @collection_name = name
  options[:capped] = true
  options[:size] ||= DEFAULT_CAP_SIZE
  options[:size] = DEFAULT_CAP_SIZE if options[:size] <= 0

  # It's OK to call createCollection if the collection already exists.
  # Size and max won't change, though.
  #
  # Note we can't use the name "create_collection" because a DB JSObject
  # does not have normal keys and returns collection objects as the
  # value of all unknown names.
  self.class.connection.create_collection(@collection_name, options)

  @console = options[:stderr]
end

Class Method Details

.connection ⇒ Object

Return the database connection. The default value is $db.



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# File 'lib/mongo_record/log_device.rb', line 49

def connection
  conn = @@connection || $db
  raise "connection not defined" unless conn
  conn
end

.connection=(val) ⇒ Object

Set the database connection. If the connection is set to nil, then $db will be used.



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# File 'lib/mongo_record/log_device.rb', line 57

def connection=(val)
  @@connection = val
end

Instance Method Details

#close ⇒ Object

Close the log. This method is a sham. Nothing happens. You may continue to use this LogDevice.



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# File 'lib/mongo_record/log_device.rb', line 108

def close
end

#write(str) ⇒ Object

Write a log message to the database. We save the message and a timestamp.



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# File 'lib/mongo_record/log_device.rb', line 101

def write(str)
  $stderr.puts str if @console
  self.class.connection.collection(@collection_name).insert({:time => Time.now, :msg => str})
end