Log to a central MongoDB from Rails apps.

1. If using Bundler, add the following to your Gemfile then refresh your dependencies by executing "bundle install":

    gem "central_logger" 

2. If you're just using gem:

    gem install central_logger 

3. Add the following line to your ApplicationController:

    include CentralLogger::Filter 

4. For use with Heroku you need to prevent the rails_log_stdout plugin from being added by Heroku:

    mkdir vendor/plugins/rails_log_stdout touch vendor/plugins/rails_log_stdout/.gitkeep 

5. If using Rails 3, SKIP this step. Otherwise, add the following to config/environment.rb:

    require 'central_logger' CentralLogger::Initializer.initialize_deprecated_logger(config) 

6. Add mongo settings to database.yml for each environment in which you want to use the Central Logger. The central logger will also look for a separate central_logger.yml or mongoid.yml (if you are using mongoid) before looking in database.yml. In the central_logger.yml and mongoid.yml case, the settings should be defined without the 'mongo' subkey.

   database.yml:

    development: adapter: mysql database: my_app_development user: root mongo: database: my_app # required (the only required setting) capsize: <%= 10.megabytes %> # default: 250MB for production; 100MB otherwise host: localhost # default: localhost port: 27017 # default: 27017 replica_set: true # default: false - Adds retries for ConnectionFailure during voting for replica set master safe_insert: true # default: false - Enable/Disable safe inserts (wait for insert to propagate to all nodes) application_name: my_app # default: Rails.application - Only really needed for non-capistrano Rails 2 deployments. Otherwise should set automatically. 

   central_logger.yml:

    development: database: my_app capsize: <%= 10.megabytes %> host: localhost port: 27017 replica_set: true 

With that in place, a new MongoDB document (record) will be created for each request and, by default will record the following information: Runtime, IP Address, Request Time, Controller, Action, Params, Application Name and All messages sent to the logger. The structure of the Mongo document looks like this:

{'action' : action_name, 'application_name' : application_name (rails root), 'controller' : controller_name, 'ip' : ip_address, 'messages' :{'info' : [ ], 'debug' : [ ], 'error' : [ ], 'warn' : [ ], 'fatal' : [ ] }, 'params' :{}, 'path' : path, 'request_time' : date_of_request, 'runtime' : elapsed_execution_time_in_milliseconds, 'url' : full_url } 

Beyond that, if you want to add extra information to the base of the document (let's say something like user_guid on every request that it's available), you can just call the Rails.logger.add_metadata method on your logger like so (for example from a before_filter):

 # make sure we're using the CentralLogger in this environment if Rails.logger.respond_to?(:add_metadata) Rails.logger.add_metadata(:user_guid => @user_guid) end 

Please see the central_log_viewer: a companion web application for querying and viewing your centralized logs.

And now, for a couple quick examples on getting ahold of this log data... First, here's how to get a handle on the MongoDB from within a Rails console:

>> db = Rails.logger.mongo_connection => #<Mongo::DB:0x102f19ac0 @slave_ok=nil, @name="my_app" ... > >> collection = db[Rails.logger.mongo_collection_name] => #<Mongo::Collection:0x1031b3ee8 @name="development_log" ... > 

Once you've got the collection, you can find all requests for a specific user (with guid):

>> cursor = collection.find(:user_guid => '12355') => #<Mongo::Cursor:0x1031a3e30 ... > >> cursor.count => 5 

Find all requests that took more that one second to complete:

>> collection.find({:runtime =>{'$gt' => 1000}}).count => 3 

Find all order#show requests with a particular order id (id=order_id):

>> collection.find({"controller" => "order", "action"=> "show", "params.id" => order_id}) 

Find all requests with an exception that contains "RoutingError" in the message or stack trace:

>> collection.find({"messages.error" => /RoutingError/}) 

Find all requests with a request_date greater than '11/18/2010 22:59:52 GMT'

>> collection.find({:request_time =>{'$gt' => Time.utc(2010, 11, 18, 22, 59, 52)}}) 

Copyright (c) 2009-2011 Phil Burrows and CustomInk, released under the MIT license