R2DBC JEEConf 2019 by Igor Lozynskyi

R2DBC as a reactive API for data access in SQL databases.
Presented at JEEConf 2019 by Igor Lozynskyi.

Transcript

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 3 3 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
14. Spring WebClient Netty Cloud Messaging WebFlux …
15. Reactive Spring Data MongoDB Cassandra Couchbase Redis
16. What about SQL?
17. ADBA R2DBC vs 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
20. ADBA https://www.oracle.com/technetwork/database/application-development/jdbc/ documentation/adba-devnexus-5391648.pdf
21. Part 2: R2DBC
22. R2DBC https://r2dbc.io
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
24. image credits: Pivotal
25. image credits: Pivotal
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
36. image credits: Pivotal
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); }
42. image credits: Pivotal
43. image credits: Pivotal
44. R2DBC Drivers / PostgreSQL / Microsoft SQL Server / H2 / MySQL/MariaDB (by community)
45. Supported databases
46. 2018 StackOverflow survey Reactive Spring Data R2DBC
47. How R2DBC drivers work?
48. r2dbc-postgres PostgreSQL wire-protocol TCP
49. r2dbc-postgres PostgreSQL
51. Where is back pressure?
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
56. Downsides of R2DBC
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
68. Q&A Thank you! /aigor /siromaha /ihor.lozinsky