![Alia vs. Cassaforte
37
Cassaforte
(let [conn (cc/connect ["127.0.0.1"])]
(cql/create-keyspace conn "cassaforte_keyspace"
(with {:replication
{:class "SimpleStrategy"
:replication_factor 1 }})))
Alia
(def cluster (alia/cluster {:contact-points ["localhost"]}))
(def session (alia/connect cluster))
(alia/execute session
(create-keyspace :alia
(if-exists false)
(with {:replication
{:class "SimpleStrategy"
:replication_factor 1}})))](https://image.slidesharecdn.com/cassandraandclojure-140715113837-phpapp02/85/Cassandra-and-Clojure-37-320.jpg)
![Cluster Object
• Entry point
• Configures relevant client options
• :contact-points
• :load-balancing-policy
• :reconnection-policy
• :retry-policy
• and more!
39
(def cluster (alia/cluster {:contact-points ["localhost"]}))](https://image.slidesharecdn.com/cassandraandclojure-140715113837-phpapp02/85/Cassandra-and-Clojure-39-320.jpg)
![Session Object
• A Session is associated with a keyspace
• Allows interacting with multiple keyspaces
40
(def cluster (alia/cluster {:contact-points [“localhost"]}))
(def session (alia/connect cluster))
(def session (alia/connect cluster) :my_keyspace)](https://image.slidesharecdn.com/cassandraandclojure-140715113837-phpapp02/85/Cassandra-and-Clojure-40-320.jpg)
Cassandra and Clojure
- 1. ©2013 DataStax. Do not distribute without consent.©2013 DataStax. Do not distribute without consent. Nick Bailey OpsCenter Architect Cassandra and Clojure 1
- 2. Who am I? • OpsCenter Architect • Monitoring/management tool for Cassandra • Organizer of Austin Cassandra Users • http://www.meetup.com/Austin-Cassandra-Users/ • Third Thursday each month. Come join! • Working with Cassandra for 4 years
- 3. Cassandra - An introduction
- 4. Cassandra - Intro • Based on Amazon Dynamo and Google BigTable papers • Shared nothing • Distributed • Predictable scaling 4 Dynamo BigTable
- 5. Users 533
- 7. Cassandra - Cluster Architecture • All nodes participate in a cluster • Shared nothing • Add or remove as needed • More capacity? Add a server 7
- 8. Cassandra - Data Distribution 8 75 0 25 50 • Each node owns 1 or more “tokens” • Each piece of data has a “partition key” • Partition key is hashed to determine token • Hashes: • Murmur3 (default) • Md5
- 9. Cassandra - Replication • Client writes to any node • Node coordinates with replicas • Data replicated in parallel • Replication factor (RF): How many copies of your data? 9
- 10. Cassandra - Failure Modes • Consistency level • How many nodes? • ONE/QUORUM/ALL 10
- 11. Cassandra - Geographically Distributed • Client writes local • Data syncs across WAN • Replication Factor per DC • Consistency Level • LOCAL_QUORUM 11 Datacenter East Datacenter West
- 12. Data Modeling - Concepts
- 13. CQL • Cassandra Query Language • SQL-like • Not Relational
- 14. Terminology • Keyspace • Table (Column Family) • Row • Column • Partition Key • Clustering Key
- 15. Data Types cqlsh:clojure_cassandra_demo> help types CQL types recognized by this version of cqlsh: ascii bigint blob boolean counter decimal double float inet int list map set text timestamp timeuuid uuid varchar varint
- 16. Advanced Concepts • Lightweight Transactions • Atomic Batches • User Defined Types (coming soon)
- 17. Data Modeling - An Example
- 18. Approaching Data Modeling • Model your queries, not your data • Generally, optimize for reads • Denormalize! • Iterate!
- 19. Basic Last.fm Clone • See songs that user X has listened to recently • See user X’s favorite songs in a specific month • See who has recently listened to artist Y • See artist Y’s most popular songs in a specific week
- 20. Basic Last.fm Clone • See songs that user X has listened to recently • One of the most common patterns/data models • Time series • Immutable (good fit for Clojure!)
- 21. Basic Last.fm Clone • See songs that user X has listened to recently SELECT song, artist, played_at FROM user_history WHERE username = ‘nickmbailey’ ORDER BY played_at DESC; • Partition key = ‘username’ • Clustering key = ‘played_at’
- 22. Basic Last.fm Clone • See songs that user X has listened to recently CREATE TABLE user_history ( username text, played_at timestamp, album text, artist text, song text, PRIMARY KEY (username, played_at) ) WITH CLUSTERING ORDER BY (played_at DESC)
- 23. Basic Last.fm Clone • See songs that user X has listened to recently • This table has a “bad” partition key CREATE TABLE user_history ( username text, played_at timestamp, album text, artist text, song text, PRIMARY KEY (username, played_at) ) WITH CLUSTERING ORDER BY (played_at DESC)
- 24. Basic Last.fm Clone • See songs that user X has listened to recently • Much better partition key CREATE TABLE user_history ( username text, year_and_month text, played_at timestamp, album text, artist text, song text, PRIMARY KEY ((username, year_and_month), played_at) ) WITH CLUSTERING ORDER BY (played_at DESC)
- 25. Basic Last.fm Clone • See songs that user X has listened to recently cqlsh:clojure_cassandra_demo> select * from user_history limit 5; username | year_and_month | played_at | album | artist | song -------------+----------------+--------------------------+--------------------------+--------------------------+------------------------- nickmbailey | 2014-06 | 2014-06-30 17:13:54-0500 | Once More 'Round The Sun | Mastodon | Halloween nickmbailey | 2014-06 | 2014-06-30 17:08:53-0500 | Once More 'Round The Sun | Mastodon | Ember City b_hastings | 2014-06 | 2014-06-30 12:57:12-0500 | Buena Vista Social Club | Buena Vista Social Club | Chan Chan zack_smith | 2014-07 | 2014-07-30 12:49:35-0500 | Awake Remix | Tycho | Awake (Com Truise Remix) zack_smith | 2014-03 | 2014-03-30 12:44:50-0500 | Awake Remix | Tycho | Awake Partition Key - unordered Clustering Key - Ordered
- 26. Basic Last.fm Clone • See user X’s favorite songs in a specific month SELECT song, artist, play_count FROM user_history WHERE username = ‘nickmbailey’ AND month = ‘July’ ORDER BY play_count DESC; • Partition key = ‘username’, ‘month’ • Clustering key = ‘play_count’? • Counters are a special case
- 27. Counters • Counter can not be part of the PRIMARY KEY • No ordering based on counter value • All non counter columns must be part of the PRIMARY KEY • Limitations due to the storage format
- 28. Basic Last.fm Clone • See user X’s favorite songs in a specific month CREATE TABLE user_song_counts ( username text, year_and_month text, artist text, song text, play_count counter, PRIMARY KEY ((username, year_and_month), artist, song))
- 29. Basic Last.fm Clone • See user X’s favorite songs in a specific month • Results unordered • Client will have to do the sorting cqlsh:clojure_cassandra_demo> select * from user_song_counts where username = 'nickmbailey' and year_and_month = '2014-07'; username | year_and_month | artist | song | count -------------+----------------+----------+-----------------------------------+------- nickmbailey | 2014-07 | Amos Lee | Tricksters, Hucksters, And Scamps | 10 nickmbailey | 2014-07 | Beck | Blackbird Chain | 1 nickmbailey | 2014-07 | Beck | Blue Moon | 4 nickmbailey | 2014-07 | Cherub | <3 | 12 nickmbailey | 2014-07 | Cherub | Chocolate Strawberries | 6
- 30. Basic Last.fm Clone • See who has recently listened to artist Y CREATE TABLE artist_history ( artist text, year_and_week text, played_at timestamp, album text, song text, username text, PRIMARY KEY ((artist, year_and_week), played_at) ) WITH CLUSTERING ORDER BY (played_at DESC)
- 31. Basic Last.fm Clone • See artist Y’s most popular songs in a specific week CREATE TABLE artist_song_counts ( artist text, year_and_week text, album text, song text, play_count counter, PRIMARY KEY ((artist, year_and_week), album, song))
- 33. Building Blocks • Java Driver • Hayt 33
- 34. Java Driver • Fully featured • Connection pooling • Failover policies • Retry policies • Sync and Async interfaces • Exposes client metrics • https://github.com/datastax/java-driver 34
- 35. Hayt • CQL DSL • Similar to Korma • Solely for building CQL strings • https://github.com/mpenet/hayt 35 (select :foo (where { :bar 1 :baz 2)}) (->raw (select :foo (where {:bar 1 :baz 2)})) > "SELECT * FROM foo WHERE bar = 1 AND baz = 2;"
- 36. Clients • Alia • https://github.com/mpenet/alia • Cassaforte • https://github.com/clojurewerkz/cassaforte • Both built on Java Driver and Hayt • Not particularly different 36
- 37. Alia vs. Cassaforte 37 Cassaforte (let [conn (cc/connect ["127.0.0.1"])] (cql/create-keyspace conn "cassaforte_keyspace" (with {:replication {:class "SimpleStrategy" :replication_factor 1 }}))) Alia (def cluster (alia/cluster {:contact-points ["localhost"]})) (def session (alia/connect cluster)) (alia/execute session (create-keyspace :alia (if-exists false) (with {:replication {:class "SimpleStrategy" :replication_factor 1}})))
- 38. Learn by Example - Alia
- 39. Cluster Object • Entry point • Configures relevant client options • :contact-points • :load-balancing-policy • :reconnection-policy • :retry-policy • and more! 39 (def cluster (alia/cluster {:contact-points ["localhost"]}))
- 40. Session Object • A Session is associated with a keyspace • Allows interacting with multiple keyspaces 40 (def cluster (alia/cluster {:contact-points [“localhost"]})) (def session (alia/connect cluster)) (def session (alia/connect cluster) :my_keyspace)
- 41. Querying • Multiple ways to query • alia/execute • Synchronous, block on result • alia/execute-async • Returns a Lamina result-channel (basically, a promise) • Optional success/error callbacks • alia/execute-chan • Returns a core.async channel • We won’t dive in to core.async now 41
- 42. Prepared Statements • Statements can be prepared server side • Better performance for common queries 42 (def prepared-statement (alia/prepare session "select * from users where user_name=?;"))
- 43. What else? • See github and docs • https://github.com/mpenet/alia • http://mpenet.github.io/alia/qbits.alia.html 43
- 44. Demo
- 45. Demo • https://github.com/nickmbailey/clojure-cassandra-demo • Built with • CCM - https://github.com/pcmanus/ccm • Alia - https://github.com/mpenet/alia • ring - https://github.com/ring-clojure/ring • compojure - https://github.com/weavejester/compojure • hiccup - https://github.com/weavejester/hiccup • least - https://github.com/Raynes/least 45
- 46. More Cassandra: http://cassandra.apache.org DataStax Drivers: https://github.com/datastax Documentation: http://www.datastax.com/docs Getting Started: http://www.datastax.com/documentation/gettingstarted/index.html Developer Blog: http://www.datastax.com/dev/blog Cassandra Community Site: http://planetcassandra.org Download: http://planetcassandra.org/Download/DataStaxCommunityEdition Webinars: http://planetcassandra.org/Learn/CassandraCommunityWebinars Cassandra Summit Talks: http://planetcassandra.org/Learn/CassandraSummit
- 47. ©2013 DataStax Confidential. Do not distribute without consent.©2013 DataStax Confidential. Do not distribute without consent. 47