Files used in a presentation on MongoDB and Ruby

basics.rb

require 'rubygems'
require 'mongo'

@con = Mongo::Connection.new

# Instance of Mongo::DB
@db  = @con['webinar']

# Instance of Mongo::Collection
@col = @db['users']

@doc = { :first  => "Kyle",
         :last   => "Banker",
         :city   => "NYC",
         :loc    => [40.1, -73],
         :status => 0
       }

id = @col.insert(@doc)

@col.update({'_id' => id})


puts "\nCursors and queries"
# Instance of Mongo::Cursor
@cursor = @col.find

# Implements Enumerable
@cursor.each do |doc|
  p doc
end

# Manual iteration
@cursor = @col.find
while @cursor.has_next?
  p @cursor.next_document
end

# Collection#find_one doesn't create a cursor
p @col.find_one

puts "\nRunning a command"
# BSON::OrderedHash (not needed in 1.9)
# Sometimes documents need ordering, as when running commands
# The command key must come first
@cmd = BSON::OrderedHash.new
@cmd['findAndModify'] = 'users'
@cmd['query']  = {:first => "Kyle"}
@cmd['update'] = {:$set => {:status => 2}}

p @db.command(@cmd)

@col.remove

# Executables
# - j2bson
# - b2json
# - mongo_console

connect.rb

require 'rubygems'
require 'logger'
require 'mongo'

# Connecting to a single mongod or to mongos
# 'localhost', 27017
Mongo::Connection.new

# Host / port parameters
Mongo::Connection.new('localhost', 27017)

# With logging
# Note: this make things slower. Not for high performance apps.
@logger = Logger.new('mongo-ruby.log')
@con = Mongo::Connection.new('localhost', 27017, :logger => @logger)
@con['test']['foo'].save({:foo => "bar"})

# Connection to a secondary or slave node
Mongo::Connection.new('localhost', 27017, :slave_ok => true)

# Using Mongo URI
Mongo::Connection.from_uri("mongo://localhost:27017")

jruby.rb

require 'rubygems'
require 'mongo'

p BSON::BSON_CODER

# Since you can build true, multi-threaded apps, connection pooling
# will be most useful here.
# pool_size = number of threads, where one thread is allocated per connection.
# timeout is the amount of time to wait for a new connection before raising an exception
# This works for ReplSetConnection too.
Mongo::Connection.new('localhost', 27017, :pool_size => 10, :timeout => 500)

om.rb

# Object mappers


# MongoDoc
# MongoMatic
# Candy
# MongoMapper
# Mongoid


# I recommend MongoMapper. However, lots of works has gone into
# the other projects. You should decide based on tests, review of the
# code base, successful projects.

# Common feautures
#  - Validation
#  - Associations (Document-document, Embedded, and Polymorphic)

om_rules_of_thumb.rb

# Rules of thumb

# 1. Know your tools.
#    - MongoDB
#    - Driver
#    - Object Mapper (Read the code!)


# 2. Don't let abstractions make you weak or lead you astray.
#    - Documents should be no more than a couple levels deep.
#    - And generally no larger than 100KB.
#    - Going against either of the above is a code smell.


# 3. Don't declare indexes in your model.
#    - An index is a migration and therefore should not be built automatically.
#    - Mongoid has a rake task for build indexes.

repl_set_connect.rb

require 'rubygems'
require 'mongo'

# Note: this assumes a replica set with three nodes on
# localhost, starting at 30000

# Basic connection
# Note: it's best to specify all seed node in your app
Mongo::ReplSetConnection.new( ['localhost', 30000], ['localhost', 30001],
                              ['localhost', 30002] )

# Ensure replica set name
Mongo::ReplSetConnection.new( ['localhost', 30000], :rs_name => "foo" )

# Distribute reads to secondaries
Mongo::ReplSetConnection.new( ['localhost', 30000], :read_secondary => true )

# Connect directly to a secondary node
Mongo::Connection.new( ['localhost', 30001], :slave_ok => true )

# Using Mongo URI
Mongo::Connection.from_uri("mongo://localhost:30001,localhost:30002")

# The failover question.
# If a replica set member fails, electing a new master can take
# time. Your application has to allow for this.

# See tests.

write_concern.rb

require 'rubygems'
require 'mongo'

# Write concern can be set on the Connection, DB, Collection,
# or individual operation. Applies to inserts, updates, and deletes.

# Writes just write to the socket. Write concen will issue a getlasterror
# command immediately after to flush the socket and ensure that no
# errors were raised on the server.

# You can run getlasterror manually. There's a driver helper.
@con = Mongo::Connection.new
@db  = @con['test']

puts "Get last error"
@db['test']['foo'].save({:foo => "baz"})
p @db.get_last_error

# Ensure that write was replicated to a total of two nodes,
# with a 500ms timeout
@db['test']['foo'].save({:foo => "bar"})
@db['test']['foo'].remove
p @db.get_last_error(:w => 0, :wtimeout => 500)

puts "Safe mode inheritance"
# These options are specified using :safe
@con = Mongo::Connection.new('localhost', 27017, :safe => true)
@db  = @con['test']
@col = @db['foo']
p @db.safe
p @col.safe

# Overriding the default safe setting
@col.save({:foo => "baz"}, :safe => false)

# More sophisticated safe settings
@con = Mongo::Connection.new('localhost', 27017)

@analytics = @con['analytics']
@app = Mongo::DB.new('app', @con, :safe => {:w => 2, :wtimout => 500})

puts "Analytics safe mode: #{@analytics.safe}"
puts "App safe mode: #{@app.safe.inspect}"