Deep Dive into Reactive Relational Database Access

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

Why reactive, why R2DBC? How to build PrestoDB R2DBC driver.

Transcript

1. / by Igor Lozynskyi Deep Dive into Reactive Relational Database Access
2. For whom this talk: / Want to build reactive apps? / Like to work with databases? / Want to learn about R2DBC? / I assume, you know what Reactive is
3. Реактивный Хардкор / Oleh Dokuka 3 3 Igor Lozynskyi
5. Agenda / Why reactive database access? / Look at R2DBC components / Build R2DBC driver
6. Part 1: Why Reactive DB access?
8. Why Reactive? / New frontier for high-efficiency apps / Fundamentally non-blocking / Paired with asynchronous behaviors / Complex stream processing / Reactive Streams Standard / Pull-push back pressure
9. MySQL DB MySQL Driver in ZD service data
10. MySQL DB MySQL Driver in ZD service
11. Why Reactive? / New frontier for high-efficiency apps / Fundamentally non-blocking / Paired with asynchronous behaviors / Complex stream processing / Reactive Streams Standard / Pull-push back pressure
12. technology radar vol. 20 by ThoughtWorks
13. Reactive Programming does NOT like blocking threads
14. Spring (5.0+) is reactive now
15. Spring WebClient Netty Cloud Messaging WebFlux …
16. Reactive Spring Data MongoDB Cassandra Couchbase Redis Neo4j* *1.0.0-beta01
17. What about SQL?
18. ADBA R2DBC vs by Oracle by Pivotal
20. ADBA / Async API for relational data access in Java / Implemented with CompletableFuture / Uses Java 9’s Flow API
21. Criticism / Does not imply back pressure / Has only ADBA-over-JDBC implementation / Slow development / Authors have neglected Reactive approach for a long time / Tiny interest in async-only API
22. ADBA https://www.oracle.com/technetwork/database/application-development/jdbc/ documentation/adba-devnexus-5391648.pdf
23. implications…
24. Part 2: R2DBC
25. R2DBC https://r2dbc.io
26. R2DBC Design principles / Based on Reactive Streams Types and Patterns / Completely non-blocking, up to the DB / Utilize wire-protocol for non-blocking implementations / Divide Client API and Driver SPI / Shrink Driver SPI
27. image credits: Pivotal
28. image credits: Pivotal
29. JDBC API vs R2DBC SPI / JDBC has the same API for: / Driver authors / Human users / Inhuman users like JPA, Jdbi, jOOQ, etc. / No-one likes using JDBC API / Many methods, most useless / Too low-level for human users / Too verbose for driver implementors
30. R2DBC SPI / ConnectionFactory / Connection / Statement / Result / RowMetadata / Row
31. 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()
32. 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)
33. R2DBC SPI - Result / Publisher<Integer> getRowsUpdated() / <T> Publisher<T> map(BiFunction<Row, RowMetadata, ? extends T> f)
34. R2DBC SPI - Row / <T> T get(Object identifier, Class<T> type)
35. SPI: Connection factory H2ConnectionConfiguration conf = H2ConnectionConfiguration.builder() .url("mem:db;DB_CLOSE_DELAY=-1;TRACE_LEVEL_FILE=4") .build(); ConnectionFactory connectionFactory = new H2ConnectionFactory(conf);
36. SPI: Simple select connectionFactory .create() .flatMapMany(conn -> conn.createStatement("SELECT currency, price FROM trades") .execute() .flatMap(result -> result .map((row, metadata) -> row.get("currency"))))
37. 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())
38. 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
39. image credits: Pivotal
40. R2DBC Client R2dbc r2dbcClient = new R2dbc(connectionFactory);
41. 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())
42. 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())
43. 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. image credits: Pivotal
45. Drivers: 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 - Pg protocol feature handles back pressure
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
56. Spring Data Repository & Transactions? @Component class TransactionalService { private CustomerRepository repository; @Transactional public Mono<Customer> save(Customer customer) { return repository.save(customer).map(it -> { if (it.firstname.equals("Dave")) { throw new IllegalStateException(); } else { return it; } }); } }
57. Downsides of R2DBC
58. JPA? / No Hibernate / No EclipseLink / No JPA so far? / No JPA at all?
59. Longer Queries / DBs rushing to deliver data / Back pressure may delay data delivery
60. Longer Transactions / Back pressure may cause more contention / JDBC may be faster than R2DBC / R2DBC may impact DB internals
61. 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. Dirty Part: Writing code!
65. PrestoDB R2DBC Driver
66. source: https://stackshare.io/presto
67. PrestoDB vs PrestoSQL
68. source: http://starburstdata.com
69. source: http://starburstdata.com HTTP
70. image credits: Pivotal PrestoDB
71. r2dbc-presto Presto wire-protocol HTTP SQL
73. Get hands dirty!
74. r2dbc-presto
75. Last Part: Moral
76. R2DBC Pros / New and shiny / Brings reactive to DB access / Active community, many connectors / Easy to implement drivers
77. R2DBC Cons / Still not GA (current: 0.8 RC1) / No JPA (Hibernate/EclipseLink) / Reactive approach may not fit SQL at all / Reactive programming is under a thread
78. Fibers & Coroutines strike back
79. Fibers/Coroutines Cons / Light-weight threads / Write blocking, synchronous code / Use JDBC/JPA / Don’t use FP, write imperative code / C#, JS has async/await / Go, Kotlin has green threads
80. Why Reactive? vs Fibers/Coroutines / New frontier for high-efficiency apps / Fundamentally non-blocking / Paired with asynchronous behaviors / Complex stream processing / Pull-push back pressure / Reactive Streams Standard Kotlin Coroutine’s Flow Java / JS / C++ / C# … May be simulated with channels
81. Summary / R2DBC won the battle against ADBA / Will have reactive DB access, soon / Spring Data drives R2DBC / Not for production yet? But soon! / It is time to try R2DBC! / Reactive vs Fibers: friends or foes?
82. Takeaways / Web on Reactive Stack (Spring Framework) / www.r2dbc.io
83. Q&A Thank you! /aigor /siromaha /ihor.lozinsky