This document summarizes Cassandra drivers and tools. It discusses the Java driver architecture including connection pooling, load balancing policies, and automatic paging. It also demonstrates Cassandra Unit for testing, the Java driver object mapper module, and Achilles object mapper with features like dirty checking. Live coding examples are provided for these tools.

1. Cassandra Drivers And Tools
DuyHai DOAN, Technical Advocate
@doanduyhai

2. Agenda!
@doanduyhai
2
Drivers
• architecture, policies, Java driver API
DevCenter (live coding demo!)
Cassandra Unit (+ live coding demo!)
Object Mapper module (+ live coding demo!)
Achilles Object Mapper (+ live coding demo!)

3. Cassandra Drivers Architecture!
Architecture!
Policies!
Java driver API!

4. Drivers list!
@doanduyhai
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• Java
• C#
• Python
• Node.js
• Ruby (1.0.0.rc1)
• C++ (beta)
• ODBC (beta)
• Clojure (community)
• Go (community)
• PHP (to be announced)

5. Connection pooling!
@doanduyhai
5
n3
n2
n4
Driver
Pool1
Pool2
Pool3
Client
Thread1
Client
Thread2
Client
Thread3

6. Connection pooling!
@doanduyhai
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n3
n2
n4
Driver
Pool1
Pool2
Pool3
Client
Thread1
Client
Thread2
Client
Thread3
1
2 3
4
5
6

7. Request Pipelining!
@doanduyhai
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Client Cassandra

8. Request Pipelining!
@doanduyhai
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Client Cassandra
StreamID
StreamID

9. Nodes Discovery!
@doanduyhai
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n2
n3
n4
n5
n6
n7
n8
Control Connection
n1 Driver

10. Round Robin Load Balancing!
@doanduyhai
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n2
n3
n4
n5
n6
n7
n8
n1 Client
1
2
3
4

11. DC Aware Load Balancing!
@doanduyhai
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Client1 DC1
⤫
Client2 DC2

12. DC Aware Load Balancing!
@doanduyhai
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⤫
Client1 DC1
Client2 DC2

13. Token Aware Load Balancing!
@doanduyhai
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n2
n3
n4
n5
n6
n7
n8
1
n1 Client
2
3
⤫

14. Combining Load Balancing Policies!
Token Aware
Round Robin DC Aware Round Robin
@doanduyhai
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extends
Load Balancing Policy
wraps
Default config

15. Automatic Failover!
@doanduyhai
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n3
n2
n4
Driver
7 6
Pool1
4 5
Pool2
Pool3
Client
Thread
⤫
1
2
3
8

16. Other policies!
@doanduyhai
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Retry policy
• write/read timeout
• node unavailable
Reconnection policy
• constant schedule
• exponential schedule

17. Statements!
@doanduyhai
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Plain statement
• convenient, one-off query
• plain string ☞ parsing overhead
INSERT INTO user(login, name, age) VALUES(‘jdoe’, ‘John DOE’, 33)’;

18. Statements!
@doanduyhai
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Prepared statements
• avoid parsing overhead
• query structure should be known ahead of time
• bound values
• named parameters
INSERT INTO user(login, name, age) VALUES(?, ?, ?)’;
INSERT INTO user(login, name, age) VALUES(:login, :name, :age)’;

19. Statements!
@doanduyhai
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Parameterized statements
• same as plain statement
• pass bound values as bytes ☞ avoid ser/deser of values
INSERT INTO user(login, name, age) VALUES(?, ?, ?)’;

20. Java Driver!
@doanduyhai
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Reference implementation
Base on asynchronous Netty library
Configurable policies
Query tracing support
Client-node compression & SSL

21. Maven dependency!
Available on Maven Central
@doanduyhai
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<dependency>
<groupId>com.datastax.cassandra</groupId>
<artifactId>cassandra-driver-core</artifactId>
<version>2.1.3</version>
</dependency>
depends on Netty, Guava, Metrics

22. Connect and Write!
@doanduyhai
22
Cluster cluster = Cluster.builder()
.addContactPoints("127.0.0.1", “another-host").build();
seed nodes (IP or DNS name)
Session session = cluster.connect("my_keyspace");
session.execute("INSERT INTO user (user_id, name, email)
VALUES (12345, 'johndoe', 'john_doe@fiction.com’)");

23. Configuration!
@doanduyhai
23
Cluster cluster = Cluster.builder()
.addContactPoints("127.0.0.1", “another-host")
.withLoadBalancingPolicy(new DCAwareRoundRobinPolicy("DC1")
.withRetryPolicy(DowngradingConsistencyRetryPolicy.INSTANCE)
.withReconnectionPolicy(new ConstantReconnectionPolicy(1000))
.build();

24. Read!
@doanduyhai
24
ResultSet resultSet = session.execute("SELECT * FROM user");
List<Row> rows = resultSet.all();
for (Row row : rows) {
Long userId = row.getLong("user_id");
String name = row.getString("name");
String email = row.getString("email");
}
Stateless ☞ thread-safe

25. Asynchronous Read!
ResultSetFuture future = session.executeAsync("SELECT * FROM user");
ResultSet resultSet = future.get(); //blocking call
List<Row> rows = resultSet.all();
for (Row row : rows) {
Long userId = row.getLong("user_id");
String name = row.getString("name");
String email = row.getString("email");
}
@doanduyhai 25

26. Asynchronous Read with CallBack!
ResultSetFuture future = session.executeAsync("SELECT * FROM user");
future.addListener(new Runnable() {
public void run() {
// Process the results here
}
}, executor);
executor = Executors .newCachedThreadPool();
or
executor = Executors .sameThreadExecutor();
@doanduyhai 26

27. Query Builder!
Query query = QueryBuilder
.select()
.all()
.from( "my_keyspace", "user")
.where(eq("login", "jdoe"));
query.setConsistencyLevel(ConsistencyLevel.ONE);
ResultSet rs = session.execute(query);
@doanduyhai 27

28. Old manual paging!
@doanduyhai
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Some time you need to fetch all table content
Manual paging:
SELECT * FROM users WHERE token(login) >= token(<last_fetched_login>)
LIMIT 100;

29. New automatic paging!
@doanduyhai
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n2
n3
n4
n5
n6
n7
n8
Query
n1 Driver
Page 1 + paging state 1

30. New automatic paging!
@doanduyhai
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n2
n3
n4
n5
n6
n7
n8
Query
n1 Driver
Page 2 + paging state 2

31. New automatic paging!
@doanduyhai
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Paging state ≈ stateless cookie
Resilient to node failure

32. Paging during node failure!
@doanduyhai
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n2
n3
n4
n5
n6
n7
n8
Query
n1 Driver
Page 1 + paging state 1

33. Paging during node failure!
@doanduyhai
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n2
n3
n4
n5
n6
n7
n8
Query
n1 Driver
Page 2 + paging state 2
⤫

34. ! "
!
Q & R

35. Dev Center
Demo

36. Cassandra Unit!
@doanduyhai
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• start an embedded Cassandra server
• useful for unit testing
• mature project, created at August 5th 2011
• designed around Thrift & Hector
• propose a JUnit rule for CQL

37. Cassandra Unit
Demo

38. Java Driver Object Mapper!
@doanduyhai
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• simple mapper
• KISS
• annotations à-la JPA (but no JPA dependencies)
• templating system à-la Spring Data

39. Java Driver Object Mapper!
Mapping
@doanduyhai
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@Table(keyspace = "mapper_module", name = "users")
public class User {
@PartitionKey
private String login;
private String name;
// getters and setters omitted...
}

40. Java Driver Object Mapper!
Usage
@doanduyhai
40
MappingManager manager = new MappingManager(session);
Mapper mapper = manager.mapper(User.class);
User user = mapper.get("jdoe@fiction.com");
mapper.saveAsync(new User("hsue@fiction.com"));
mapper.delete("jdoe@fiction.com");

41. Java Driver Object Mapper!
Accessors (SpringData template-like) definition
@doanduyhai
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@Accessor
interface UserAccessor {
@Query("SELECT * FROM users LIMIT :max")
Result<User> firstNUsers(@Param("max") int limit);
}

42. Java Driver Object Mapper!
@doanduyhai
42
Accessors usage
UserAccessor accessor = manager.createAccessor(UserAccessor.class);
List<User> users = accessor.firstNUsers(10).all();
for (User user : users) {
System.out.println( profile.getAddress().getZip() );
}

43. Java Driver Object Mapper
Demo

44. Achilles!
@doanduyhai
44
Why ?
• started in late 2012, when mapper module did not exists
• more involved and more features than the mapper module
• different annotations set (may converge)

45. Achilles
Demo

46. Dirty Checking!
@doanduyhai
46
Dirty checking, why is it important ?
• 1 user ≈ 8 mutable fields
• × n denormalizations = n update combinations
• and not even counting multiple fields updates …

47. Dirty Checking!
@doanduyhai
47
• Are you going to manually generate n prepared statements for all
possible updates ?
• Or just use dynamic plain string statements and get some perf
penalty ?

48. Dirty Checking!
@doanduyhai
48
//No read-before-write
ContactEntity proxy = manager.forUpdate(ContactEntity.class, contactId);
proxy.setFirstName(…);
proxy.setLastName(…); //type-safe updates
proxy.setAddress(…);
manager.update(proxy);

49. Dirty Checking!
@doanduyhai
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Proxy
Setters interception
DirtyMap
Empty
Entity
PrimaryKey

50. Dirty Checking!
@doanduyhai
50
• Dynamic statement generation
UPDATE contacts SET firstname=?, lastname=?,address=?
WHERE contact_id=?
prepared statements are cached, of course

51. Main API!
@doanduyhai
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manager.insert(entity)
manager.update(entity)
manager.remove(entity)
manager.find(Entity.class, primaryKey)

52. Advanced Features!
@doanduyhai
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Counter
Batch mode
Strategies (insert, naming)
Options
Asynchronous

53. Documentation!
@doanduyhai
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Comprehensive Github WIKI
Twitter-clone demo app (demo.achilles.io)
Versioned documentation (HTML & PDF)
JavaDoc

54. RoadMap!
@doanduyhai
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C* 2.1 user defined types (UDT)
Query-templates à-la Spring Data
Reactive ? (RxJava)
ElasticSearch integration (@olivierbourgain)

55. ! "
!
Q & R

56. Thank You
@doanduyhai
duy_hai.doan@datastax.com
https://academy.datastax.com/