Reactive Relational Database Connectivity Mark Paluch • Spring Data Project Lead, R2DBC Contributor • @mp911de

Unless otherwise indicated, these slides are © 2013-2019 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Reactive Programming ● High-efficiency applications ● Fundamentally non-blocking ● No opinion on async ● Key differentiators: (pull-push) back pressure, flow control 2

Unless otherwise indicated, these slides are © 2013-2019 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Subscriber Publisher Subscribe Data Demand

Unless otherwise indicated, these slides are © 2013-2019 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Subscriber Publisher Subscribe Data request(n)

Unless otherwise indicated, these slides are © 2013-2019 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ WebFlux and WebClient 5 @GetMapping("/health") Mono compositeHealth() { return Mono.zip( webClient.get().uri("https://alpha-service/health") .retrieve().bodyToMono(Health.class), webClient.get().uri("https://bravo-service/health") .retrieve().bodyToMono(Health.class)) .map(t -> composite(t.getT1(), t.getT2())); }

Unless otherwise indicated, these slides are © 2013-2019 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Roadblocks ● Barriers to using Reactive everywhere ● Data Access ● MongoDB, Apache Cassandra, Redis ● No Relational Database Access 6

Unless otherwise indicated, these slides are © 2013-2019 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 7 A specification designed from the ground up for reactive programming https://r2dbc.io

Unless otherwise indicated, these slides are © 2013-2019 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Dependencies ● Reactive Streams ● Java 8 8

Unless otherwise indicated, these slides are © 2013-2019 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Design Principles ● Embrace Reactive Types and Patterns ● Non-blocking, all the way to the database ● Documented specification ● Shrink the driver SPI ● Enable multiple "humane" APIs 9

Unless otherwise indicated, these slides are © 2013-2019 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Driver SPI ● JDBC: same API for humane API and inhumane SPI for alternative clients like JPA, jOOQ, Jdbi, etc. ● API that users didn't like using and driver authors didn't like implementing ● Duplicating effort implementing the same "humane" affordances like ? binding 10

Unless otherwise indicated, these slides are © 2013-2019 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Driver SPI: ConnectionFactory 11 Publisher create() ConnectionFactoryMetadata getMetadata()

Unless otherwise indicated, these slides are © 2013-2019 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Driver SPI: Connection 12 Publisher beginTransaction() Publisher close() Publisher commitTransaction() Batch createBatch() Publisher createSavepoint(String name) Statement createStatement(String sql) Publisher releaseSavepoint(String name) Publisher rollbackTransaction() Publisher rollbackTransactionToSavepoint(String name) Publisher setTransactionIsolationLevel(IsolationLevel isolationLevel)

Unless otherwise indicated, these slides are © 2013-2019 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Driver SPI: Statement 13 Statement add() Statement bind(String name, Object value) Statement bind(int index, Object value) Statement bindNull(String name, Class> type) Statement bindNull(int index, Class> type) Statement returnGeneratedValues(String… columnNames) Publisher execute()

Unless otherwise indicated, these slides are © 2013-2019 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Driver SPI: Result and Row 14 Publisher getRowsUpdated() Publisher map(BiFunction f) T get(String identifier, Class type); Object get(String identifier); T get(int index, Class type); Object get(int index);

Unless otherwise indicated, these slides are © 2013-2019 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Simple Select 15 Publisher values = connectionFactory.create() .flatMapMany(conn -> conn.createStatement("SELECT value FROM test") .execute() .flatMap(result -> result.map((row, metadata) -> row.get("value", 
 String.class))))

Unless otherwise indicated, these slides are © 2013-2019 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Transactional Update 16 Publisher results = connectionFactory.create() .flatMapMany(conn -> conn.beginTransaction() .thenMany(conn.createStatement("INSERT INTO test VALUES($1)") .bind("$1", 100).add() .bind("$1", 200).execute()) .delayUntil(p -> conn.commitTransaction()) .onErrorResume(t -> conn.rollbackTransaction().then(Mono.error(t))))

Unless otherwise indicated, these slides are © 2013-2019 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Great! But a Bit Verbose. ● Minimal set of implementation specific operations ● Definitely usable, but very verbose and prone to errors ● Explicit transaction management is analogous to try-catch- finally-try-catch in JDBC ● We need a "humane" client API. In fact we need many humane client APIs! 17

Unless otherwise indicated, these slides are © 2013-2019 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ R2DBC Client 18 Flux values = r2dbc.withHandle(handle -> handle.select("SELECT value FROM test") .mapRow(row -> row.get("value", String.class)))

Unless otherwise indicated, these slides are © 2013-2019 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Parametrized Statement 19 Flux updatedRows = r2dbc.withHandle(handle -> handle.createUpdate("INSERT INTO test VALUES($1, $2)") .bind("$1", 100).bind("$2", 200).add() .bind("$1", 300).bind("$2", 400).execute())

Unless otherwise indicated, these slides are © 2013-2019 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Transactional Update 20 Flux updatedRows = r2dbc.inTransaction(handle -> handle.createUpdate("INSERT INTO test VALUES($1, $2)") .bind("$1", 100).bind("$2", 200).add() .bind("$1", 300).bind("$2", 400).execute())

Unless otherwise indicated, these slides are © 2013-2019 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Spring Data R2DBC

Unless otherwise indicated, these slides are © 2013-2019 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Spring Data R2DBC 22 DatabaseClient client = DatabaseClient.create(connectionFactory); Flux rows = client .execute("SELECT * FROM person WHERE name = :name") .bind("name", "John Doe") .as(Person.class) .fetch() .all();

Unless otherwise indicated, these slides are © 2013-2019 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ R2DBC Repositories 23 interface CustomerRepository extends ReactiveCrudRepository { @Query("SELECT * FROM … WHERE lastname = :lastname") Flux findByLastname(String lastname); } repository.findByLastname("Matthews") .doOnEach(c -> System.out.println(c.firstname))

Unless otherwise indicated, these slides are © 2013-2019 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Spring Data R2DBC ● Functional-reactive declaration of data access ● Fluent API ● Support for Transactions ● Named parameter support (Dialect-aware) ● Repositories ● Kotlin Coroutines extensions 24

Unless otherwise indicated, these slides are © 2013-2019 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Demo

Unless otherwise indicated, these slides are © 2013-2019 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Atomic Operations ● Application and Database transactions ● Classic implementations Thread-bound 26

Unless otherwise indicated, these slides are © 2013-2019 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Reactive Transactions ● Application and Database transactions ● Pattern is still correct 27

Unless otherwise indicated, these slides are © 2013-2019 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Reactive Transactions ● Application and Database transactions ● Pattern is still correct ● Bind transactional state to Subscription ● Reactor Context 28

Unless otherwise indicated, these slides are © 2013-2019 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Reactive Transactions 29 PersonRepository people; AddressRepository addresses; @Transactional Mono savePerson(Person person, Address address) { return people.save(person) .then(addresses.save(address)).then(); }

Unless otherwise indicated, these slides are © 2013-2019 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Programmatic Reactive Transactions 30 PersonRepository people; AddressRepository addresses; R2dbcTransactionManager txManager; TransactionalOperator rxtx = TransactionalOperator.create(txManager); Mono saved = people.save(person) .then(addresses.save(address)) .as(rxtx::transactional).then();

Unless otherwise indicated, these slides are © 2013-2019 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Getting Started with R2DBC ● Available from Maven Central ● start.spring.io 31

Unless otherwise indicated, these slides are © 2013-2019 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Getting Started with R2DBC 32 io.r2dbc r2dbc-bom Arabba-SR2 pom import io.r2dbc r2dbc-h2

Unless otherwise indicated, these slides are © 2013-2019 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Getting Started with R2DBC 33 io.r2dbc r2dbc-bom Arabba-SR2 pom import io.r2dbc r2dbc-h2

Unless otherwise indicated, these slides are © 2013-2019 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ R2DBC Connection URL 34 r2dbc:pool:postgresql://localhost:5432/database?key=value ConnectionFactory connectionFactory = ConnectionFactories.get("r2dbc:postgresql://myhost/database? driver=foo");

Unless otherwise indicated, these slides are © 2013-2019 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Spring Boot Starter for R2DBC ● ConnectionFactory configuration ● R2DBC TransactionManager ● Embedded H2 support ● Actuator integration ● Schema.sql and Data.sql support ● @DataR2dbcTest 35

Unless otherwise indicated, these slides are © 2013-2019 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ 36

Unless otherwise indicated, these slides are © 2013-2019 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ R2DBC Ecosystem

Unless otherwise indicated, these slides are © 2013-2019 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ R2DBC Ecosystem ● Specification document ● R2DBC SPI ● R2DBC Proxy ● Connection Pooling ● Client Implementations ● Spring Data R2DBC ● r2dbc-client ● Kotysa ● Drivers ● Google Cloud Spanner ● H2 ● Microsoft SQL Server ● MySQL Driver (r2dbc-mysql, jasync-sql) ● MariaDB ● PostgreSQL ● SAP Hana 38

Unless otherwise indicated, these slides are © 2013-2019 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Planned R2DBC Clients ● MyBatis (#1444) ● JDBI (#1454) ● jOOQ (#6298) ● Querydsl (#2468) ● Helidon (#581) ● Liquibase (CORE-3419) ● Flyway (#2502) ● Exposed (#456) ● Testcontainers (#1003) ● Go vote for a client you want to see happen. 39

Unless otherwise indicated, these slides are © 2013-2019 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Planned R2DBC Drivers ● MariaDB (alpha-state by MariaDB Inc.) ● Firebird (Jaybird) investigating ● Oracle investigating ● DB2 foundation in the works (started with a vert.x driver first) ● Ask your vendor! 40

Unless otherwise indicated, these slides are © 2013-2019 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Non-blocking SQL Database Endeavours ● Various individual driver projects (NDBC, Jasync, Vert.x, …) ● Hibernate Rx ● ADBA: Asynchronous Database API ● OJDBC 20 with Reactive Extensions ● Oracle looking into R2DBC 41

Unless otherwise indicated, these slides are © 2013-2019 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Wrap up!

Unless otherwise indicated, these slides are © 2013-2019 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ What Can You Do Today? ● End-to-end reactive non-blocking database communication ● Batching ● BLOB/CLOB ● Extensive Type Conversion ● Savepoints ● Transactions ● Leveraging Database-specific features ● ServiceLoader-based Driver discovery ● Connection URLs ● Categorized exceptions (Bad grammar, Data integrity violation, …) 43

Unless otherwise indicated, these slides are © 2013-2019 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ R2DBC Roadmap ● Started as experiment in early 2018 ● Available as 0.8.0 SR2 ● 0.9.0: Stored Procedures, Extended transaction spec, EventProvider 44

Unless otherwise indicated, these slides are © 2013-2019 Pivotal Software, Inc. and licensed under a Creative Commons Attribution-NonCommercial license: http://creativecommons.org/licenses/by-nc/3.0/ Resources ● Website
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 https://groups.google.com/forum/ #!forum/r2dbc ● Monthly Call
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Thank you. r2dbc.io @mp911de