The document discusses new Cassandra drivers that utilize a CQL binary protocol and provide an asynchronous, failover-capable architecture. Key points include the drivers supporting CQL's denormalized data model, request pipelining, notifications, configurable load balancing and retry policies, and downgrading consistency levels automatically if necessary.

1. New Cassandra Drivers in
Depth
Michaël Figuière
@mfiguiere

2. Speaker
Michaël Figuière
@mfiguiere
©2012 DataStax 2

3. CQL: the new face of Cassandra
• CQL 3
• Simpler Data Model using denormalized Tables
• SQL-like query language
• Schema definition
• CQL Binary Protocol
• Introduced in Cassandra 1.2 (CASSANDRA-2478)
• Designed for CQL 3
• Opens doors for Streaming, Notifications, ...
• Thrift will keep being supported by Cassandra
©2012 DataStax 3

4. CQL3 Denormalized Model
CQL3 Query Language comes with a new Data Model abstraction made of
denormalized, statically defined tables
Data duplicated over several tables
©2012 DataStax 4

5. CQL3 Data Model
Timeline Table
user_id tweet_id author body
gmason 1735 phenry Give me liberty or give me death
gmason 1742 gwashington I chopped down the cherry tree
ahamilton 1767 jadams A government of laws, not men
ahamilton 1794 gwashington I chopped down the cherry tree
Partition Clustering
Key Key
©2012 DataStax 5

6. CQL3 Data Model
Timeline Table
user_id tweet_id author body
gmason 1735 phenry Give me liberty or give me death
gmason 1742 gwashington I chopped down the cherry tree
ahamilton 1767 jadams A government of laws, not men
ahamilton 1794 gwashington I chopped down the cherry tree
CQL
CREATE TABLE timeline (
user_id varchar,
tweet_id timeuuid,
author varchar,
body varchar,
PRIMARY KEY (user_id, tweet_id));
©2012 DataStax 6

7. CQL3 Data Model
Timeline Table
user_id tweet_id author body
gmason 1735 phenry Give me liberty or give me death
gmason 1742 gwashington I chopped down the cherry tree
ahamilton 1767 jadams A government of laws, not men
ahamilton 1794 gwashington I chopped down the cherry tree
Timeline Physical Layout
[1735, author] [1735, body] [1742, author] [1742, body]
gmason
gwashington I chopped down the... phenry Give me liberty or give...
[1767, author] [1767, body] [1794, author] [1794, body]
ahamilton
gwashington I chopped down the... jadams A government of laws...
©2012 DataStax 7

8. Current Drivers Architecture
CQL API Thrift API OO API DB API
Thrift RPC Thrift RPC
Client Library CQL Driver
* This is a simplified view of drivers architecture. Details vary from one language to another.
©2012 DataStax 8

9. New Drivers Architecture
DB API CQL API OO API
CQL Native Protocol
Next Generation Driver
* This is a simplified view of drivers architecture. Details vary from one language to another.
©2012 DataStax 9

10. DataStax Java Driver
• Reference Implementation
• Asynchronous architecture based on Netty
• Prepared Statements Support
• Automatic Fail-over
• Node Discovery
• Cassandra Tracing Support
• Tunable policies
• LoadBalancingPolicy
• ReconnectionPolicy
•
©2012 DataStax
RetryPolicy
10

11. Request Pipelining
Client Cassandra
Without
Request Pipelining
With
Client Cassandra Request Pipelining
©2012 DataStax 11

12. Notifications
Node
Client
Node
Node
Without
Notifications
With
Notifications
Node
Client
Node
Node
©2012 DataStax 12

13. Asynchronous Architecture
Node
Client
Thread
Node
Client
Driver
Thread
Node
Client
Thread
Node
©2012 DataStax 13

14. Asynchronous Architecture
Node
Client
Thread 6
1 Node
Client
Driver 2
Thread 3
Node
5
4
Client
Thread
Node
©2012 DataStax 14

15. LoadBalancingPolicy
public interface LoadBalancingPolicy {
HostDistance distance(Host host);
Iterator<Host> newQueryPlan(Query query);
[...]
}
©2012 DataStax 15

16. DCAwareRoundRobinPolicy
Datacenter A
Local nodes are
queried first, if non Client Node
are available, the
request will be sent Client Node
to a remote node.
Node
Client
Client Node
Client Node
Node
Client
Datacenter B
©2012 DataStax 16

17. TokenAwarePolicy
Nodes that own a
Replica of the data
being read or written
by the query will be
contacted first.
Replica
Node Node
Client Replica
Node
Node
Replica
Node
©2012 DataStax 17

18. RetryPolicy
public interface RetryPolicy {
RetryDecision onReadTimeout(Query query, ConsistencyLevel cl, [...] );
RetryDecision onWriteTimeout(Query query, ConsistencyLevel cl, [...] );
RetryDecision onUnavailable(Query query, ConsistencyLevel cl, [...] );
public static class RetryDecision {
public static enum Type { RETRY, RETHROW, IGNORE };
private final Type type;
private final ConsistencyLevel retryCL;
[...]
}
}
©2012 DataStax 18

19. Downgrading Consistency
If the requested
Consistency Level
cannot be reached
(QUORUM here), a
second request with a
lower CL is sent
automatically. Node Replica
Client Node
Replica
Node
Replica
©2012 DataStax 19

20. Connect and Write
Cluster cluster = Cluster.builder()
.addContactPoints("10.0.0.1", "10.0.0.2")
.build();
Session session = cluster.connect("myKeyspace");
session.execute(
"INSERT INTO user (user_id, name, email)
VALUES (12345, 'johndoe', 'john@doe.com')"
);
©2012 DataStax 20

21. Read
ResultSet rs = session.execute("SELECT * FROM test");
List<Row> rows = rs.all();
for (Row row : rows) {
String userId = row.getString("user_id");
String name = row.getString("name");
String email = row.getString("email");
}
©2012 DataStax 21

22. Asynchronous Read
ResultSetFuture future =
session.executeAsync("SELECT * FROM test");
for (Row row : future.get()) {
String userId = row.getString("user_id");
String name = row.getString("name");
String email = row.getString("email");
}
©2012 DataStax 22

23. Prepared Statements
PreparedStatement ps =
session.prepare("SELECT * FROM users WHERE id = ?");
BoundStatement bs =
session.execute(ps.bind("123")).one().getInt("age");
bs.setString("k");
int age = session.execute(bs).one().getInt("age");
age = session.execute(ps.bind("123")).one().getInt("age");
©2012 DataStax 23

24. Query Builder
String query = "SELECT a,b,"C"
FROM foo
WHERE a IN (127.0.0.1,127.0.0.3)
AND "C"='foo'
ORDER BY a ASC,b DESC LIMIT 42;";
Query select =
select("a", "b", quote("C")).from("foo")
.where(in("a", InetAddress.getByName("127.0.0.1"),
InetAddress.getByName("127.0.0.3")))
.and(eq(quote("C"), "foo"))
.orderBy(asc("a"), desc("b"))
.limit(42);
©2012 DataStax 24

25. Object Mapping
@Table(name = "user")
public class User { public enum Gender {
@PartitionKey @EnumValue("m")
@Column(name = "user_id") MALE,
private String userId;
@EnumValue("f")
private String name; FEMALE;
}
private String email;
private Gender gender;
}
©2012 DataStax 25

26. Inheritance
@Table(name = "catalog")
@Inheritance(
@InheritanceValue("tv")
subClasses = {Phone.class, TV.class},
public class TV
column = "product_type"
extends Product {
)
public abstract class Product {
private float size;
}
@Column(name = "product_id")
private String productId;
private float price;
private String vendor;
private String model;
}
©2012 DataStax 26

27. Betas now available!
https://github.com/datastax/

28. Stay Tuned!
blog.datastax.com
@mfiguiere