Mongodb on Ruby And Rails (froscon 2010)

on rails

froscon 2010, st. augustin.

jan krutisch <jan@krutisch.de>
http://jan.krutisch.de/

Sonntag, 22. August 2010

mongodb wtf? lol!?


document database


NoS
QL
inclu
ded!

document database


10gen


open source

http://github.com/mongodb/mongo

id title descr pos_lat pos_lng


no ﬁxed schema
no migrations


rich data structure


{
"_id" : ObjectId("4c00245062610475a005afcd"),
"address" : "Bernstorffstr. 174n22767 HamburgnDE",
"description" : null,
"position" : {
"lat" : 53.5600912,
"lng" : 9.9596977
},
"tags" : [
"hausarzt",
"naturheilverfahren",
"akupunktur",
"allgemeinmedizin"
],
"title" : "Dr. med. Lilo Eisenbarth",
"loxicon_id" : 808261
}


✗

BSON


BInary Serialized jsON

http://bsonspec.org/

Lightweight


Traversable


Efﬁcient


Wire


Storage


rich queries


conceptually close to SQL


easy to grasp


ﬂexible


language integration


on top: map/reduce


Scaling


Master/Slave replication


Replica Sets (1.6)


Primary

Member Member


Primary

Member Primary


Member

Member Primary


Autosharding (1.6)


Durability


No single server
durability!


fsyncs every 60s
(conﬁgurable)


Use Replication!


Use write propagation
locking


Single Server Durability
planned for 1.8


mongo console


$ mongo


> use test
switched to db test

db.quotes.save({
text: "You can observe a lot just by watching.",
from: "Yogi Berra", created_at: new Date()
});

db.quotes.save({
text: "Silence is one of the hardest arguments to refute.",
from: "Josh Billings", created_at: new Date()
});


Indexing


Same concept as with
SQL databases


You want them


Sort order


Unique


Compound


Geospatial


map/reduce


we can haz it, too


function() {
this.tags.forEach(function(z) {
emit(z, {count: 1});
});
}

function(key, values) {
var total = 0;
values.forEach(function(v) { total += v });
return {count: total}
}


(it‘s not fast...)


security


simple user/password
auth


per database


read only is possible


one more thing


GridFS


Binary ﬁelds in BSON
< 4MB


GridFS saves ﬁles in
chunks


I‘m in u‘r rubies,
querying teh MongoDB!


core driver


mongo / bson_ext


ODMs / Libs


mongo_mapper


mongoid


Find examples here:
http://github.com/halfbyte/mongo_ruby_examples


Basic driver usage


init


require 'mongo'

@connection = Mongo::Connection.new
@db = @connection.db("test")


insert/upsert


doc = {
:text => "You can observe a lot just by watching.",
:from => "Yogi Berra",
:created_at => Time.now
}
@db['quotes'].insert(doc)


doc = @db['quotes'].find_one(id)

doc[:from] = "Yogi Berra, famous baseball player"

@db['quotes'].save(doc)


atomic updates


@db['quotes'].update(
{"from" => "Yogi Berra"},
{"$inc" => {"reads" => 1 } }
)


$inc $addToSet
$set $pop
$unset $pull
$push $pullAll
$pushAll $


getting a whole collection


@db['quotes'].find.each do |row|
puts row.inspect
end


exact query


@db['quotes'].find(:from => "Yogi Berra")


more queries


100.times do |i|
db['numbers'].insert({"i" => i})
end


db['numbers'].find("i" => {"$lt" => 2})


$lt <
$gt >
$lte <=
$gte >=
$ne !=


@db['people'].find(:tags => {"$in" => ['cool']})


obj = {
"_id"=>BSON::ObjectID('4c706af16261040680000369'),
"name"=>"Vernon Kreiger",
"address"=>{
"street"=>"536 Haleigh Locks",
"city"=>"Port Kiannahaven",
"zip"=>"80730-0214",
"country"=>"Fakistan"
},
"tags"=>["cool", "weird"]
}


$in IN (2,3,4)
$nin NOT IN
$all [2,3] ~ [1,2,3]


$mod yah, RLY
$size okay
$exists NOT NULL
$type huh?


@db['people'].find("address.city" => /haven/)


Sorting


@db['people'].find().sort("address.street")


Pagination


@db['numbers'].find.sort("i").limit(10)


@db['numbers'].find.sort("i").limit(10).skip(50)


Counting


@db['numbers'].find.count


Distinct


@db['people'].distinct('tags').inspect


Group


Poor mans map/reduce


Map / Reduce


map = <<-END
function() {
this.tags.forEach(function(z) {
emit(z, {count: 1});
});
}
END
reduce = <<-END
function(key, values) {
var total = 0;
values.forEach(function(v) { total += v.count });
return {count: total}
}
END

collection = @db['people'].map_reduce(
map, reduce
)


Indexes


db['people'].create_index("tags")

db['people'].drop_index("tags_1")

db['people'].index_information


GridFS usage


grid = Mongo::Grid.new(@db)

id = grid.put("You can put Strings in here",
:filename => 'test.txt')

file = grid.get(id)

file.filename
file.read

grid.delete(id)

grid.put(
File.open("/Users/jankrutisch/Dropbox/Photos/IMGP8989.jpg")
)


fs = Mongo::GridFileSystem.new(db)

fs.open("test.txt", "w") do |f|
f.write "You can put stuff in here"
end

fs.open("test.txt", "r") do |f|
puts f.read
end

fs.delete("test.txt")


Capped collections


@db.create_collection('capped_numbers',
:capped => true,
:max => 50
)

@db.create_collection('capped_numbers',
:capped => true,
:size => 1024 * 64
)


ODMs


John Nunemaker
@jnunemaker


is in production


documentation?


how to


rails initializer


# config/initializers/mongo_mapper.rb
File.open(File.join(Rails.root, 'config/mongodb.yml'), 'r') do |f|
@settings = YAML.load(f)[Rails.env]
end
MongoMapper.connection = Mongo::Connection.from_uri(@settings["connection"]) if @settings["connection"]

MongoMapper.database = @settings["database"]


a simple example


MongoMapper.connection = @connection
MongoMapper.database = "test"

class Quote
include MongoMapper::Document
key :from
key :text
key :views, Integer
timestamps!
end


ﬁnders


Quote.where(:from => 'Yogi Berra').all

Quote.where(:from => 'Yogi Berra').limit(5).sort(:from.desc).all


embedded docs


class Person
key :name
one :address
key :tags, Array
end

class Address
key :street
key :city
key :country
key :zip
end


person = Person.first
address = Person.first.address


scopes


class Person
scope :tagged, lambda { |tag| where(:tags.in => [tag]) }
end

puts Person.tagged('cool').first.inspect


new website coming soon


Durran Jordan
(of Hashrocket)


Two major versions


1.x (1.9.x) targeting
Rails 2.3.x


2.x (2.0beta) targeting
Rails 3.0


Good documentation


File.open(File.join(RAILS_ROOT, 'config/mongodb.yml'), 'r') do |f|
@settings = YAML.load(f)[RAILS_ENV]
end

Mongoid::Config.instance.from_hash(@settings)


class Quote
include Mongoid::Document
include Mongoid::Timestamps
field :from
field :text
field :views, :type => Integer
end


Quote.where(:from => 'Yogi Berra').all

Quote.where(:from => 'Yogi Berra').limit(5).order_by(:from.desc).all


class Person
field :name
embeds_one :address
field :tags, :type => Array
end

class Address
field :street
field :city
field :country
field :zip
end


More features


mongoid tries to be
clever


(using the „dirty“ ﬂags)


(it‘s probably better to
bypass the ODM
sometimes)


external libraries for
both


mongo_mapper > grip


mongoid > mongoid_grid


Other noteworthy
libraries


Candy


mongodoc

http://github.com/leshill/mongodoc


mongo-record

http://github.com/mongodb/mongo-record

mongomodel

http://github.com/spohlenz/mongomodel

mongo_queue

http://github.com/Skiz/mongo_queue

resque-mongo

http://github.com/ctrochalakis/resque-mongo

my account


Installation was easy


(when on right platform)


setting up replication


$ mongod --master
or
master = true # mongodb.conf

$ mongod --slave --source
slaveserver.example.com

slave = true
source = slaveserver.example.com


(see example on github)


OpLog size!


„security“


memory usage?


limits?


stability?


I


thanks for listening.
‣ http://www.mongodb.org/
‣ http://www.mongoid.org/
‣ http://github.com/jnunemaker/mongo_mapper
‣ http://github.com/halfbyte/mongo_ruby_examples

‣ jan@krutisch.de
‣ http://jan.krutisch.de/
‣ http://github.com/halfbyte/
‣ http://twitter.com/halfbyte
‣ http://www.mindmatters.de/


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