R2DBC started as an experiment to enable integration of SQL databases into systems that use reactive programming models. Now it specifies a robust specification that can be implemented to manage data in a fully-reactive and completely non-blocking fashion.

1. Creating Fully Reactive
Solutions with R2DBC
Reactive programming with relational databases

2. Who is this guy?
Rob Hedgpeth
Developer Relations @ MariaDB
robh@mariadb.com
@probablyrealrob
rhedgpeth

3. Reactive programming
with databases

4. What is it?

5. A B
C
@probablyrealrob

6. A B
C
@probablyrealrob

7. A B
C
@probablyrealrob

8. How can it be done?

9. reactive programming
/rēˈaktiv/ /ˈprōˌgramiNG/
A declarative programming paradigm concerned with data streams and the
propagation of change.
@probablyrealrob

10. Streaming data
Publisher Subscriber
Send all the data
@probablyrealrob
Backlog
Data
Data
Data
...

11. The Anatomy of a Data Stream
Variables
changes in data
Starting event
initiates stream of data
Error
disruption in data
Completion
all data is processed
Time
@probablyrealrob

12. Back Pressure
@probablyrealrob

13. Non-blocking Back Pressure
Publisher Subscriber
Push stream of
N data items
Request N data items
@probablyrealrob

14. Reactive Streams
Publisher Subscriber
Subscription
onSubscribe
request(n)
cancel()
onNext*
(onError | onComplete)
@probablyrealrob

15. Reactive Streams API
public interface Publisher<T> {
public void subscribe(Subscriber<? super T> s);
}
public interface Subscriber<T> {
public void onSubscribe(Subscription s);
public void onNext(T t);
public void onError(Throwable t);
public void onComplete();
}
public interface Subscription {
public void request(long n);
public void cancel();
}
@probablyrealrob
Project Reactor

16. Why is this important?

17. Reactive database interactions
● Highly efficient applications...from top to bottom
● Fundamentally non-blocking
● Back pressure
@probablyrealrob

18. JDBC Limitations
Reactive App
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19. R2DBC

20. What is it?

21. Reactive Relational Database Connectivity
R2 DB C
@probablyrealrob

22. Goals and design principles
✓ Provide a completely open specification (Apache v2 license)
✓ Be completely non-blocking, all the way to the database
✓ Utilize Reactive Streams Types and Patterns
✓ Provide a minimal set of operations that are implementation specific
✓ Enable “humane” APIs to be built on top of the driver
@probablyrealrob

23. Reactive App
R2DBC
@probablyrealrob

24. R2DBC Service-Provider Interface (SPI)
io.r2dbc.spi.ConnectionFactory
io.r2dbc.spi.ConnectionFactoryMetadata
io.r2dbc.spi.ConnectionFactoryProvider
io.r2dbc.spi.Result
io.r2dbc.spi.Row
io.r2dbc.spi.RowMetadata
io.r2dbc.spi.Batch
Fully Support Partially Support
io.r2dbc.spi.Connection
io.r2dbc.spi.Statement
io.r2dbc.spi.ColumnMetaData
https://github.com/r2dbc/r2dbc-spi
@probablyrealrob
v. 0.8.4

25. SPI - Connection Factory
package io.r2dbc.spi;
import org.reactivestreams.Publisher;
public interface ConnectionFactory {
Publisher<? extends Connection> create();
ConnectionFactoryMetadata getMetadata();
}
@probablyrealrob
Reactive Streams

26. SPI - Connection
package io.r2dbc.spi;
import org.reactivestreams.Publisher;
public interface Connection {
Publisher<Void> beginTransaction();
Publisher<Void> close();
Publisher<Void> commitTransaction();
Batch createBatch();
Statement createStatement(String sql);
ConnectionMetadata getMetadata();
...
}
Lots of other methods
@probablyrealrob
Reactive Streams

27. SPI - Statement
package io.r2dbc.spi;
import org.reactivestreams.Publisher;
public interface Statement {
Publisher<? extends Result> execute();
Statement add();
Statement bind(int index, Object value);
Statement bind(String name, Object value);
Statement bindNull(int index, Class<?> type);
Statement bindNull(String name, Class<?> type);
}
@probablyrealrob
Reactive Streams

28. SPI - Result
package io.r2dbc.spi;
import org.reactivestreams.Publisher;
import java.util.function.BiFunction;
public interface Result {
Publisher<Integer> getRowsUpdated();
<T> Publisher<T> map(BiFunction<Row, RowMetadata, ? extends T>
mappingFunction);
}
Reactive Streams
@probablyrealrob

29. SPI - Row
package io.r2dbc.spi;
import java.util.function.BiFunction;
public interface Row {
@Nullable
<T> T get(int index, Class<T> type);
@Nullable
<T> T get(String name, Class<T> type);
...
}
A couple default methods
@probablyrealrob

30. How can you use it?

31. R2DBC Drivers
@probablyrealrob

32. Establishing a connection
// Specify connection details
MariadbConnectionConfiguration config
= MariadbConnectionConfiguration.builder()
.host("127.0.0.1")
.port(3306)
.username("app_user")
.password("Password123!")
.build();
@probablyrealrob
// Specify connection details
MariadbConnectionConfiguration config
= MariadbConnectionConfiguration.builder()
.host("127.0.0.1")
.port(3306)
.username("app_user")
.password("Password123!")
.build();

33. Establishing a connection
// Create a new ConnectionFactory object
MariadbConnectionFactory connFactory
= new MariadbConnectionFactory(config);
// Obtain a Connection object from a ConnectionFactory
MariadbConnection conn = connFactory.create().block();
@probablyrealrob

34. SELECT
MariadbStatement selectStatement = conn.createStatement("select * from todo.tasks");
Publisher<MariadbResult> selectPublisher = selectStatement.execute();
Flux.from(selectPublisher)
.flatMap(
res -> res.map(
(row, metadata) -> {
int id = row.get(0, Integer.class);
String description = row.get(1, String.class);
Boolean completed = row.get(2, Boolean.class);
return new Task(id,description,completed);
})
).subscribe(task -> { // Do something with task });
Project Reactor
@probablyrealrob
Publisher<T> == Flux<Task>

35. But...
@probablyrealrob

36. R2DBC Clients
● Spring Data R2DBC
● Kotysa
● jOOQ
● JDBI
● Liquibase
@probablyrealrob
Data Access / Persistence Layer
R2DBC Driver
Database
Application

37. Next Steps
Just the tip of the iceberg

38. https://r2dbc.io/
robh@mariadb.com
@probablyrealrob
rhedgpeth
https://github.com/mariadb-corporation/mariadb-connector-r2dbc
Current Version = 0.8.4 RELEASE
Dev Version = 0.9.0.M1