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MongoDB - case study

Sebastian Nowak

3 marca 2010

NoSQL

NoSQL - po co?

ACID nie zawsze jest potrzebny
RDBMS nie radzą sobie z dużym wolumenem danych (TB,
PB)
elastyczność

NoSQL

NoSQL - po co?

ACID nie zawsze jest potrzebny
RDBMS nie radzą sobie z dużym wolumenem danych (TB,
PB)
elastyczność

NoSQL - wady
Godne zaufania?

NoSQL

CouchDB
MongoDB
Redis
Neo4j
Memcachedb

MongoDB - właściwości

napisane w C++


napisane w C++
dokumenty składuje jako BSON


napisane w C++
zaprojektowane by pracować w chmurze


napisane w C++
UTF-8


napisane w C++
UTF-8
protokół binarny


napisane w C++
UTF-8
protokół binarny
sterowniki do wielu języków


napisane w C++
UTF-8
protokół binarny
GridFS


napisane w C++
UTF-8
protokół binarny
GridFS
map-reduce, JavaScript

Capped collections

Idealne do składowania:
logów
próbek pomiarów (round robin?)
db.createCollection("books");
db.createCollection("probes",{capped:true, size:86400});

Insert - save
doc = { title:"Ruby wzorce projektowe", author:"Russ
Olsen", tags:["oop","ruby"] };
db.books.save(doc);
db.books.save({ title:”The Ruby Way”, :author:”Obie Fernandez”,
tags[”ruby”]});

Select - ﬁnd
db.books.findOne();
db.books.find();
db.books.find({title:"The Ruby Way"});
db.books.find({tags:"ruby"});
db.books.find({}, {title:1});
db.books.find().skip(10).limit(10);
db.books.find({tags:{$size: 2}});
db.books.find({title:/Ruby/});
db.books.find({author:{$in:["Obie Fernandez", "Russ
Olsen", "Gabierl Garcia Marquez"]}});
Inne modyﬁkatory: $ne, $in, $nin, $exist, $mod, $all, $size,
$where

Select - group
db.books.group({
key:author:true,
cond:,
reduce: function(obj,prev) { prev.count++; },
initial:{count:0}
});

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development:
database: ratemymodel_development

test:
database: ratemymodel_test

production:
host:
port: 9099
database: ratemymodel_production

initializers/mongodb.rb

conf = File.read("#{RAILS_ROOT}/config/database.yml")
db_conf = YAML.load(conf)[RAILS_ENV]
db_conf["host"] ||= "127.0.0.1"
db_conf["port"] ||= 27017

logger = Logger.new("#{RAILS_ROOT}/log/#{RAILS_ENV}_mongodb.log")

MongoMapper.connection = Mongo::Connection.new(db_conf["host"], db_conf["port"]
:logger => logger)
MongoMapper.database = db_conf["database"]

test/test helper.rb

class ActiveSupport::TestCase
# Drop all columns after each test case.
def teardown
MongoMapper.database.collections.each do |coll|
coll.remove
end
end

# Make sure that each test case has a teardown
# method to clear the db after each test.
def inherited(base)
base.define_method teardown do
super
end
end
end

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Rails::Initializer.run do |config|
config.gem ’mongo_mapper’
config.gem ’haml’
config.gem ’will_paginate’
config.gem ’hoptoad_notifier’
config.gem ’carrierwave’
config.gem ’newrelic_rpm’

config.frameworks -= [:active_record]
config.metals = ["GridFile"]
end

app/models/model.rb

# This class represents a model saved in application.
class Model
include MongoMapper::Document
include MongoMapper::FindRandom

# Fields definition
key :name, String, :required => true
key :description, String, :required => true
key :tags, Array
key :wins, Integer, :default => 0
key :defeats, Integer, :default => 0
key :ratio, Float, :default => 0
key :user_id, ObjectId

# Associations
belongs_to :user
many :assets, :dependent => :destroy

# Use created_at and updated_at timestamps
timestamps!
end

CarrierWave — konﬁguracja

# CarrierWave configuration
CarrierWave.configure do |config|
config.grid_fs_database = MongoMapper.database.name
config.grid_fs_host = MongoMapper.connection.host
config.grid_fs_access_url = "/images"
end

./script/generate uploader asset

app/uploaders/asset uploader.rb

class AssetUploader < CarrierWave::Uploader::Base
include CarrierWave::RMagick

storage :grid_fs

def store_dir
"assets/#{model.id}"
end

version :thumb { process :resize_to_fill => [200, 200] }

version :comparable { process :resize_to_fill => [450,450] }

def extension_white_list
%w(jpg jpeg png)
end
end

app/models/asset.rb

# Asset connected with model. It could be photo image etc.
class Asset
include MongoMapper::Document
include MongoMapper::FindRandom

# Uploader for image
mount_uploader :image, AssetUploader

# Fields definition
key :model_id, ObjectId, :required => true

# Callbacks
after_destroy :remove_image_from_db

# Associations
belongs_to :model
end

>> @asset.image.url
=> "/images/assets/4b6f009f00090d3b0c000002/10769300.jpg"
>> @asset.image.comparable.url
=> "/images/assets/4b6f009f00090d3b0c000002/comparable_10769300.jpg"
>> @asset.image.thumb.url
=> "/images/assets/4b6f009f00090d3b0c000002/thumb_10769300.jpg"

app/metals/grid ﬁle.rb

class GridFile
def self.call(env)
if env["PATH_INFO"] =~ /^/images/assets/(.+)$/
key = "assets/" + $1
if ::GridFS::GridStore.exist?(MongoMapper.database, key)
::GridFS::GridStore.open(MongoMapper.database, key, ’r’) do |file|
[200, {’Content-Type’ => file.content_type}, [file.read]]
end
else
[404, {’Content-Type’ => ’text/plain’}, [’File not found.’]]
end
else
[404, {’Content-Type’ => ’text/plain’}, [’File not found.’]]
end
end
end

http://www.mongodb.org/display/DOCS/Home
http://mongotips.com/
http://github.com/jnunemaker/mongomapper
http://github.com/jnicklas/carrierwave
http://guides.rubyonrails.org/rails on rack.html
http://railstips.org/blog/archives/2009/12/18/why-i-think-
mongo-is-to-databases-what-rails-was-to-frameworks/
http://blog.boxedice.com/2010/02/28/notes-from-a-
production-mongodb-deployment/

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