Slides from my cassandra talk at Railsconf 2010, not sure how useful they'll be without context, but people were asking.

1. Cassandra &
CassandraObject
Michael Koziarski
michael@koziarski.com

2. Intro to Me

7. I Don’t Have To Scale

8. Intro to Cassandra

10. Distributed

11. Fault Tolerant

12. Elastic

13. The Ring
A
F B
E C
D

14. The Ring
A
F B
E C
D

15. The Ring
A
F B
E C
D

16. The Ring
A
F B
E C
D

17. The Ring
A
F B
E C
D

18. The Ring
A
F B
E C
D

19. The Ring
A
F B
E C
D

20. The Ring
someKey
A
F B
E C
D
RandomPartitioner OrderPreservingPartitioner
MD5(key) key

21. Replication Factor
someKey
A
F B
E C
D
RF = 2

22. Replication Factor
someKey
A
F B
E C
D
RF = 3

23. Consistency Level
GET
'someKey'
A
F B
E C
D
ConsistencyLevel.ONE

24. Consistency Level
GET
'someKey'
A
F B
E C
D
ConsistencyLevel.ONE

25. Consistency Level
GET
'someKey'
A
F B
E C
D
ConsistencyLevel.ONE

26. Consistency Level
GET
'someKey'
A
F B
E C
D
ConsistencyLevel.ONE

27. Consistency Level
GET
'someKey'
A
F B
E C
D
ConsistencyLevel.QUORUM

28. Consistency Level
GET
'someKey'
A
F B
E C
D
ConsistencyLevel.QUORUM

29. Consistency Level
GET
'someKey'
A
F B
E C
D
ConsistencyLevel.QUORUM

30. Consistency Level
GET
'someKey'
A
F B
E C
D
ConsistencyLevel.ALL

31. Consistency Level
GET
'someKey'
A
F B
E C
D
ConsistencyLevel.ALL

32. Consistency Level
GET
'someKey'
A
F B
E C
D
ConsistencyLevel.ALL

33. Consistency Level
GET
'someKey'
A
F B
E C
D
ConsistencyLevel.ALL

34. Fault Tolerance
GET
'someKey'
A
F DEAD
E C
D
ConsistencyLevel.QUORUM

35. Fault Tolerance
GET
'someKey'
A
F DEAD
E C
D
ConsistencyLevel.QUORUM

36. Fault Tolerance
GET
'someKey'
A
F
E C
D

37. Elastic
NEW
A
F B
E C
D

38. Elastic
NEW
A
F B
E C
D

39. Data Model

40. Key Value Store
Some
someKey
Value

41. Column Store

42. Column

43. Column
firstName Michael

44. Row (Column Family)
firstName Michael
someKey
lastName Koziarski

45. Row (Super Column Family)
firstName Michael
someSubColumn
lastName Koziarski
someKey
firstName Kate
otherSubColumn
lastName Koziarski

46. JSON

47. Column
{
'name': 'first_name',
'value': 'Michael',
'timestamp': 1276040575
}

48. Column
{
'first_name': "Michael"
}

49. Column Family
Users["koz"] = {
'first_name': 'Michael',
'last_name': 'Koziarski'
}

50. Column Family
Users["koz"] = {
'first_name': 'Michael',
'last_name': 'Koziarski'
}

51. Column Family
Users["koz"] = {
'first_name': 'Michael',
'last_name': 'Koziarski'
}

52. Column Family
Users["koz"] = {
'first_name': 'Michael',
'last_name': 'Koziarski'
}

53. Super Column Family
UserAddresses["koz"] = {
"home" : {
"suburb": "Berhampore"
"city": "Wellington",
"country": "New Zealand"
},
"office" : {
"suburb": "CBD"
"city": "Wellington",
"country": "New Zealand"
}
}

54. Don’t let the name fool
you

55. One to Many
Timeline["nzkoz"] = {
uuid_one: "http://twitter.com/chadfowler/status/15740739666",
uuid_two: "http://twitter.com/dhh/status/15740689762",
uuid_three: "http://twitter.com/glv/status/15740546908"
}
<ColumnFamily CompareWith="TimeUUIDType" Name="Timeline"/>

56. Modeling

57. Schema Driven
Modeling

58. Start with your Data

59. Model
User
firstName
lastName
dateOfBirth

60. Figure out the Queries

61. Query
SELECT firstName, lastName
FROM `users`
WHERE dateOfBirth < '1992-­‐06-­‐09'

62. Query
SELECT dateOfBirth
FROM `users`
WHERE firstName = 'Michael'
AND
lastName = 'Koziarski'

63. Query
SELECT firstName, lastName
FROM `users`
WHERE YEAR(dateOfBirth) = 1980

64. Query
SELECT COUNT(DISTINCT firstName)
FROM `users`
WHERE dateOfBirth < '1992-­‐06-­‐09'

65. Cassandra Limitations

66. No WHERE

67. No WHERE
Kinda

68. No ORDER

69. No ORDER
Kinda

70. No COUNT

71. No COUNT
Kinda

72. No SUM

73. Query Driven
Modeling

74. Start with the Queries

75. Populate a data model
which enables them

76. Modeling Example

77. Users
Users["koz"] = {
'first_name': "Michael",
'last_name': "Koziarski"
}

78. Users
Users["koz"] = {
'first_name': "Michael",
'last_name': "Koziarski"
}
connection.get(:Users, "koz")

79. Koziarski Family
UsersByLastName["koziarski"] = {
uuid_one: "koz"
uuid_two: "kate"
}

80. Koziarski Family
UsersByLastName["koziarski"] = {
uuid_one: "koz"
uuid_two: "kate"
}
connection.get(:UsersByLastName, "koziarski").values.map do |key|
connection.get(:Users, key)
end

81. Share my Birthday
UsersByDOB["1980-­‐08-­‐15"] = {
uuid_one: "koz"
}

82. Share my Birthday
UsersByDOB["1980-­‐08-­‐15"] = {
uuid_one: "koz"
}
connection.get(:UsersByDOB, "1980-­‐08-­‐15")

83. Users Born in 1980
UsersByDOB["1980-­‐08-­‐15"] = {
uuid_one: "koz"
}

84. Users Born in 1980
UsersByDOB["1980-­‐08-­‐15"] = {
uuid_one: "koz"
}
connection.get_range(:UsersByDOB, :start=>"1980", :finish=>"1981")

85. Users Born in 1980
UsersByDOB["1980-­‐08-­‐15"] = {
uuid_one: "koz"
}
connection.get_range(:UsersByDOB, :start=>"1980", :finish=>"1981")
Only with OrderPreservingPartitioner

86. A Column Family per
Query

87. Do you really need
Cassandra?

88. CassandraObject

89. class Customer < CassandraObject::Base
attribute :first_name, :type => :string
attribute :last_name, :type => :string
attribute :date_of_birth, :type => :date
attribute :signed_up_at, :type => :time_with_zone
validate :should_be_cool
key :uuid
index :date_of_birth
association :invoices, :unique=>false, :inverse_of=>:customer
private
def should_be_cool
unless ["Michael", "Anika", "Evan", "James"].include?(first_name)
errors.add(:first_name, "must be that of a cool person")
end
end
end

90. Motivations

91. Prove ActiveModel

92. Learn Cassandra

93. Have a fun Side Project

94. Solve my Scaling
Problems

95. Solve my Scaling
Problems

96. Mostly AR Compatible

97. Not Compatible
def index
@people = @customer.people.order(params[:order]).
limit(params[:limit]).
where(...)
end

98. Compatible
def create
@person = Customer.new params[:customer]
if @person.save
redirect_to @person
else
render :action=>'new'
end
end

99. Compatible
<%= form_for(@customer) do |customer| %>
<%= customer.error_messages %>
<%= customer.text_field :first_name %>
<%= customer.submit "Save" %>
<% end %>

100. Walkthrough

101. class Customer < CassandraObject::Base
attribute :first_name, :type => :string
attribute :last_name, :type => :string
attribute :date_of_birth, :type => :date
attribute :signed_up_at, :type => :time_with_zone
validate :should_be_cool
key :uuid
index :date_of_birth
association :invoices, :unique=>false, :inverse_of=>:customer
private
def should_be_cool
unless ["Michael", "Anika", "Evan", "James"].include?(first_name)
errors.add(:first_name, "must be that of a cool person")
end
end
end

102. class Invoice < CassandraObject::Base
attribute :number, :type=>:integer
attribute :total, :type=>:float
attribute :gst_number, :type=>:string
# indexes can have a single entry also.
index :number, :unique=>true
# bi-­‐directional associations with read-­‐repair support.
association :customer, :unique=>true, :inverse_of=>:invoices
# Read migration support
migrate 1 do |attrs|
attrs["total"] ||= rand(2000) / 100.0
end
migrate 2 do |attrs|
attrs["gst_number"] = "66-­‐666-­‐666"
end
key :natural, :attributes => :number
end

103. Attributes
attribute :first_name, :type => :string
attribute :last_name, :type => :string
attribute :date_of_birth, :type => :date
attribute :signed_up_at, :type => :time_with_zone
attribute :number, :type => :integer
attribute :total, :type => :float
attribute :gst_number, :type => :string

104. Attributes
attribute :first_name, :type => :string
@customer.first_name = "Michael"
@customer.attributes= {:first_name=>"Michael"}

105. Validations
validate :should_be_cool
def should_be_cool
unless ["Michael", "Anika", "Evan", "James"].include?(first_name)
errors.add(:first_name, "must be that of a cool person")
end
end

106. Validations
validate :should_be_cool
def should_be_cool
unless ["Michael", "Anika", "Evan", "James"].include?(first_name)
errors.add(:first_name, "must be that of a cool person")
end
end
@customer.first_name = "Marcel"
@customer.valid? # => false

107. Validations
validates_confirmation_of :tos
validates_format_of :gst_number, :with=> /.../
validates_length_of :first_name, :max=>123

108. Keys

109. Key Selection Matters

110. Key Selection Matters
UsersByDOB["1980-­‐08-­‐15"] = {
uuid_one: "koz"
}
connection.get_range(:UsersByDOB, :start=>"1980", :finish=>"1981")

111. Keys
key :uuid

112. Keys
key :uuid
"bf1ba5da-­‐735a-­‐11df-­‐8b47-­‐377649cf993b"

113. Keys
key :natural, :attributes => :number

114. Custom Key Factories
key RedisKeyFactory.new(REDIS_CONNECTION, "customer_key")

115. Custom Key Factories
class RedisKeyFactory
def initialize(connection, key)
@connection, @key = connection, key
end
def next_key(object)
@connection.incr(@key)
end
# Parse should create a new key object from the 'to_param' format
def parse(string)
string.to_i
end
# create should create a new key object from the cassandra format.
def create(string)
string.to_i
end
end

116. Migrations

117. Migrations
class AddLicenseNameToArticle < ActiveRecord::Migration
def self.up
add_column :articles, :license_name, :string, :default=>"Exclusive"
execute "UPDATE articles SET license_name = 'Exclusive'
WHERE price_first IS NOT NULL"
execute "UPDATE articles SET license_name = 'Syndicated'
WHERE price_first IS NULL"
end
def self.down
remove_column :articles, :license_name
end
end

118. Migrations
{
'price_first': 45,
'schema_version': 0
}

119. Migrations
class Article < CassandraObject::Base
attribute :price_first, :type=>:float
attribute :license_name, :type=>:string
migrate 1 do |attrs|
if attrs[:price_first]
attrs[:license_name] = "Exclusive"
else
attrs[:license_name] = "Syndicated"
end
end
end

120. Migrations
class Article < CassandraObject::Base
attribute :price_first, :type=>:float
attribute :license_name, :type=>:string
migrate 1 do |attrs|
if attrs[:price_first]
attrs[:license_name] = "Exclusive"
else
attrs[:license_name] = "Syndicated"
end
end
end
@article = Article.get("some-­‐old-­‐story")
@article.license_name # => "Exclusive"

121. Migrations
{
'price_first': 45,
'schema_version': 1,
'license_name': 'Exclusive'
}

122. Indexes

123. Indexes
class Article < CassandraObject::Base
attribute :slug, :type=>:string
key :uuid
index :slug, :unique=>true
end
connection.insert(:ArticlesBySlug, @article.slug,
{UUID.new => @article.key})

124. Indexes
class Article < CassandraObject::Base
attribute :slug, :type=>:string
key :uuid
index :slug, :unique=>true
end
connection.insert(:ArticlesBySlug, @article.slug,
{UUID.new => @article.key})
@article = Article.find_by_slug("some-­‐slug")

125. Indexes
class Article < CassandraObject::Base
attribute :publication_date, :type=>:date
key :uuid
index :publication_date, :unique=>false
end
connection.insert(:ArticlesByPublicationDate,
@article.publication_date,
{UUID.new => @article.key})

126. Indexes
class Article < CassandraObject::Base
attribute :publication_date, :type=>:date
key :uuid
index :publication_date, :unique=>false
end
connection.insert(:ArticlesByPublicationDate,
@article.publication_date,
{UUID.new => @article.key})
@article = Article.find_all_by_publication_date(Date.today -­‐ 1)

127. Indexes
class Article < CassandraObject::Base
attribute :publication_date, :type=>:date
key :uuid
index :publication_date, :unique=>false
end
connection.insert(:ArticlesByPublicationDate,
@article.publication_date,
{UUID.new => @article.key})
@article = Article.find_all_by_publication_date(Date.today -­‐ 1)

128. Read-Repair
results = []
connection.get(:ArticlesByPublicationDate, date).each do |(uuid, key)|
article = Article.get(uuid)
if article.publication_date != date
connection.delete(:ArticlesByPublicationDate, date, uuid)
else
results << article
end
end
results

129. Associations

130. Associations
class Invoice < CassandraObject::Base
association :customer, :unique=>true, :inverse_of=>:invoices
end
class Customer < CassandraObject::Base
association :invoices, :unique=>false, :inverse_of=>:customer
end
@customer.invoices.create! params[:invoice]
@invoice.customer

131. Project Status

132. Very Beta

133. In Flux

134. Taking Patches

135. Thanks!
Michael Koziarski
michael@koziarski.com
http://github.com/NZKoz/cassandra_object
http://cassandra.apache.org/