R2DBC JEEConf 2019 by Igor Lozynskyi
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This document discusses building reactive database drivers with R2DBC. It covers how Spring supports reactive database access, an introduction to R2DBC including its design principles and SPI. It then discusses how R2DBC drivers work internally and provides examples of using R2DBC with Spring Data repositories. While R2DBC brings reactivity to database access, it is still immature and has limitations compared to blocking approaches like JPA.
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R2DBC JEEConf 2019 by Igor Lozynskyi
- 1. / by Igor Lozynskyi Building a Reactive DB driver with R2DBC
- 2. For whom this talk: / Want to build reactive apps? / Want to have reactive database access? / Want lo learn about R2DBC? / I assume, you know what Reactive is
- 3. Реактивный Хардкор / Oleh Dokuka 33 Igor Lozynskyi
- 5. Agenda / Spring & reactive database access / R2DBC / Look inside R2DBC driver
- 6. Part 1: Spring & Reactive DB access
- 8. Why Reactive? / New frontier for high-efficiency apps / Fundamentally non-blocking / Paired with asynchronous behaviors / Pull-push back pressure
- 9. MySQL DB MySQL Driver in ZD service
- 10. Why Reactive? / New frontier for high-efficiency apps / Fundamentally non-blocking / Paired with asynchronous behaviors / Pull-push back pressure
- 11. technology radar vol. 20 by ThoughtWorks
- 12. Reactive Programming does NOT like blocking threads
- 13. Spring (5.0+) is reactive now
- 16. What about SQL?
- 17. ADBA R2DBCvs by Oracle by Pivotal
- 18. ADBA / New async API for relational data access in Java / Implemented with CompletableFuture / Uses Java 9’s Flow API
- 19. Criticism / Does not imply back pressure / Has only ADBA-over-JDBC implementation / Slow development / Authors have neglected Reactive approach for a long time / No clear timeline
- 21. Part 2: R2DBC
- 23. R2DBC Design principles / Based on Reactive Streams Types and Patterns / Be completely non-blocking, up to the DB / Utilize wire-protocol for non-blocking implementations / Divide Client API and Driver SPI / Shrink Driver SPI
- 26. JDBC API / JDBC has the same API for: / Driver authors / Human users / Inhuman users like JPA, Jdbi, jOOQ, etc. / No-one likes using JDBC API
- 27. R2DBC SPI / ConnectionFactory / Connection / Statement / Result / RowMetadata / Row / Batch
- 28. R2DBC SPI - Connection / Batch createBatch() / Statement createStatement(String sql) / Publisher<Void> beginTransaction() / Publisher<Void> commitTransaction() / Publisher<Void> rollbackTransaction() / Publisher<Void> rollbackTransactionToSavepoint(String name) / Publisher<Void> setTransactionIsolationLevel(IsolationLevel level) / Publisher<Void> createSavepoint(String name) / Publisher<Void> releaseSavepoint(String name) / Publisher<Void> close()
- 29. R2DBC SPI - Statement / Statement add() / Statement bind(Object identifier, Object value) / Statement bindNull(Object identifier, Class<?> type) / Publisher<? extends Result> execute() / Statement returnGeneratedValues(String... columns)
- 30. R2DBC SPI - Result / Publisher<Integer> getRowsUpdated() / <T> Publisher<T> map(BiFunction<Row, RowMetadata, ? extends T> f)
- 31. R2DBC SPI - Row / <T> T get(Object identifier, Class<T> type)
- 32. SPI: Connection factory H2ConnectionConfiguration conf = H2ConnectionConfiguration.builder() .url("mem:db;DB_CLOSE_DELAY=-1;TRACE_LEVEL_FILE=4") .build(); ConnectionFactory connectionFactory = new H2ConnectionFactory(conf);
- 33. SPI: Simple select connectionFactory .create() .flatMapMany(conn -> conn.createStatement("SELECT currency, price FROM trades") .execute() .flatMap(result -> result .map((row, metadata) -> row.get("currency"))))
- 34. SPI: Batch insert connectionFactory .create() .flatMapMany(conn -> conn.createStatement( “INSERT INTO trades (currency, market, price) “ + "VALUES (?, ?, ?)") .bind(0, "EUR").bind(1, "TD").bind(2, 7.0).add() .bind(0, "UAH").bind(1, "TX").bind(2, 6.0).add() .execute())
- 35. SPI: Transactions connectionFactory .create() .flatMapMany(conn -> conn.beginTransaction() .thenMany(conn.createStatement( "INSERT INTO trades (currency, market, price) " + "VALUES (?, ?, ?)") .bind(0, "UAH").bind(1, "TX").bind(2, "B") .execute()) .delayUntil(p -> conn.commitTransaction()) .onErrorResume(t -> conn .rollbackTransaction() .then(Mono.error(t)))) try-with-resources
- 37. R2DBC Client R2dbc r2dbcClient = new R2dbc(connectionFactory);
- 38. R2DBC Client r2dbcClient .withHandle(handle -> handle.createUpdate( "INSERT INTO trades (currency, market, price) " + "VALUES ($1, $2, $3)") .bind("$1", "UAH").bind("$2", "TX").bind("$3", 3.4) .execute())
- 39. R2DBC Client: Transactions r2dbcClient .inTransaction(handle -> handle.createUpdate( "INSERT INTO trades (currency, market, price) " + "VALUES ($1, $2, $3)") .bind("$1", "UAH").bind("$2", "TX").bind("$3", 3.4) .execute())
- 40. SPI: Transactions connectionFactory .create() .flatMapMany(conn -> conn.beginTransaction() .thenMany(conn.createStatement( "INSERT INTO trades (currency, market, price) " + "VALUES (?, ?, ?)") .bind(0, "UAH").bind(1, "TX").bind(2, "B") .execute()) .delayUntil(p -> conn.commitTransaction()) .onErrorResume(t -> conn .rollbackTransaction() .then(Mono.error(t))))
- 41. Spring Data Repository public interface UsSalesR2dbcRepository extends R2dbcRepository<UsSalesDataDto, String> { @Query("select * from us_sales_by_districts") Flux<UsSalesDataDto> findAll(); @Query("select * from us_sales_by_districts, where code=:code") Mono<UsSalesDataDto> findById(@Param("code") String code); }
- 44. R2DBC Drivers / PostgreSQL / Microsoft SQL Server / H2 / MySQL/MariaDB (by community)
- 46. 2018 StackOverflow survey Reactive Spring Data R2DBC
- 52. Portal
- 53. Using R2DBC with Spring Data
- 54. public interface UsSalesR2dbcRepository extends R2dbcRepository<UsSalesDataDto, String> { @Query("select * from us_sales_by_districts") Flux<UsSalesDataDto> findAll(); @Query("select * from us_sales_by_districts, where code=:code") Mono<UsSalesDataDto> findById(@Param("code") String code); } Spring Data R2DBC
- 55. Spring Data Repository & Transactions? @Transactional class TransactionalDatabaseClient
- 57. JPA? / No Hibernate / No EclipseLink / No JPA so far? / No JPA at all?
- 58. Longer Queries / DBs rushing to deliver data / Back pressure may delay data delivery
- 59. Longer Transactions / Back pressure may cause more contention / JDBC faster then R2DBC / R2DBC may impact DB internals
- 60. Wire-protocol / Should allow data streaming / Should allow back pressure / Cancellation / Implement Reactive Streams semantics / Multiplexing? / RSocket?
- 62. Fun Part: Demo
- 63. App (WebFlux) PostgreSQL TCP Reactive Spring Data R2DBC Driver
- 64. R2DBC Pros / New and shiny / Brings reactive to DB access / More active community than ADBA’s / Easy to implement drivers (compared to JDBC)
- 65. R2DBC Cons / Not mature enough (current: 1.0.0.M7) / May be beaten by ADBA / No JPA (Hibernate/EclipseLink) / Reactive approach may not fit SQL at all
- 66. Summary / ADBA vs R2DBC battle is still going on / May soon have reactive DB access / Spring Data drives R2DBC / Not for production yet! / Don’t afraid to try R2DBC!
- 67. Takeaways / Web on Reactive Stack (Spring Framework) / www.r2dbc.io