Deep Dive into Reactive Relational Database Access (Devoxx Ukraine 2019)

R2DBC as a reactive API for data access in SQL databases.
Presented at Devoxx Ukraine 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. Реактивный Хардкор / Oleh Dokuka 2 2 Igor Lozynskyi
4. Agenda / Why reactive DB access? / Look at R2DBC / Build a toy R2DBC driver / I assume, you know what Reactive is
5. Part 1: Why Reactive DB access?
6. Reactive Programming / Nonblocking / Usually asynchronous / Declarative / Processing streams / Resilient / Back pressure / Reactive Streams Standart / High-efficiency
8. Spring (5.0+) is reactive now
9. Spring Netty WebFlux WebClient Cloud Messaging …
10. Reactive Spring Data MongoDB Cassandra Couchbase ElasticSearch Redis Neo4j* *1.0.0-beta01
11. What about SQL?
12. JDBC / Nonblocking / Usually asynchronous / Declarative / Processing streams / Resilient / Back pressure / Reactive Streams Standart / Blocks Threads JDK 1.1 1997 year
13. Reactive Relational DataBase Connectivity
14. Part 2: R2DBC https://r2dbc.io
15. R2DBC by Pivotal NDBC Jasync Vert.x async DB clients ADBA
16. 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
17. Dependencies / Reactive Streams (1KB jar) / Java 8
18. image credits: Pivotal Other Databases H2
19. image credits: Pivotal Other Databases H2
20. R2DBC SPI - Specification
21. JDBC API vs R2DBC SPI for drivers for drivers for clients
22. R2DBC SPI / ConnectionFactory / Connection / Statement / Result / RowMetadata / Row image credits: Jonathan Bregler
23. 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()
24. 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)
25. R2DBC SPI - Result / Publisher<Integer> getRowsUpdated() / <T> Publisher<T> map(BiFunction<Row, RowMetadata, ? extends T> f)
26. R2DBC SPI - Row / <T> T get(Object identifier, Class<T> type)
27. SPI: Connection factory H2ConnectionConfiguration conf = H2ConnectionConfiguration.builder() .url("mem:db") .build(); ConnectionFactory connectionFactory = new H2ConnectionFactory(conf);
28. SPI: Simple select connectionFactory .create() .flatMapMany(conn -> conn.createStatement("SELECT currency, price FROM trades") .execute() .flatMap(result -> result .map((row, metadata) -> row.get("currency"))))
29. 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())
30. 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
31. image credits: Pivotal Other Databases H2
32. R2DBC Client R2dbc r2dbcClient = new R2dbc(connectionFactory); 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())
33. 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())
34. Stream Processing
35. Stream processing pgConnection .createStatement("LISTEN user_login_notifications”) .execute() .flatMap(PostgresqlResult::getRowsUpdated) .subscribe(); pgConnection .getNotifications() .map(Notification::getParameter) .subscribe(event -> { // do something useful });
36. image credits: Pivotal Other Databases H2
37. Drivers: supported databases
38. 2018 StackOverflow survey Reactive Spring Data R2DBC
39. Using R2DBC with Spring
40. Spring Boot Starter for R2DBC / Driver discovery by URL (r2dbc:mysql://…) / ConnectionFactory / TransactionManager / Actuator integration / Embedded H2 / schema.sql and data.sql / @DataR2dbcTest
41. 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
42. 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; } }); } }
43. Caveats / Requires Project Reactor (Context) / May not work with RxJava / Some Rx operators may cancel subscription / Flux.take(10) / Flux.next()
44. How R2DBC drivers work?
45. r2dbc-postgres PostgreSQL wire-protocol TCP
46. r2dbc-postgres PostgreSQL
48. Where is back pressure?
49. Portal - Pg protocol feature handles back pressure 2 4
50. Downsides of R2DBC
51. JPA? / No Hibernate / No EclipseLink / No JPA so far? / But: Hibernate Rx
52. Longer Queries / DBs rushing to deliver data / Back pressure may delay data delivery
53. Longer Transactions / Back pressure may cause more contention / JDBC may be faster than R2DBC / R2DBC may impact DB internals
54. Wire-protocol & DB design requirements / Should allow data streaming / Should allow back pressure / Support query cancellation / Conform to Reactive Streams semantics / Connection multiplexing? / RSocket?
55. R2DBC Goodies / r2dbc-proxy / r2dbc-pool (connection pooling)
56. R2DBC Roadmap / 0.8.0 GA in 2019 / 0.9.0: / Extended transaction API / EventProvider / Stored Procedures / More R2DBC support in DB-related libraries
57. Fun Part: Demo
58. App (WebFlux) PostgreSQL TCP Reactive Spring Data R2DBC Driver
59. Dirty Part: Writing code!
60. PrestoDB R2DBC Driver
61. source: https://stackshare.io/presto
62. PrestoDB vs PrestoSQL
63. source: http://starburstdata.com
64. source: http://starburstdata.com HTTP
65. image credits: Pivotal PrestoDB
66. r2dbc-presto Presto wire-protocol HTTP SQL
67. What we need? / Java / R2DBC SPI / Project Reactor / Java 11 HTTP client (or reactor-netty) / JSON parsing libs / Presto instance
68. Get hands dirty! coding session
69. r2dbc-presto
70. Last Part: Moral
71. R2DBC Pros / New and shiny / Brings reactive to DB access / Active community, huge momentum / Easy to implement drivers
72. R2DBC Cons / Still not GA (current: 0.8 RC2) / No JPA (Hibernate/EclipseLink) / Reactive approach may not fit SQL / Reactive programming is under a thread
73. Fibers & Coroutines attack
74. Fibers/Coroutines Cons / Light-weight threads / C#, JS has async/await / Go, Kotlin has green threads / Write blocking, synchronous code / Don’t use FP, write imperative code / Use JDBC/JPA
75. / Nonblocking / Usually asynchronous / Declarative / Processing streams / Resilient / Back pressure / Reactive Streams Standart Reactive vs Fibers/Coroutines Kotlin Coroutine’s Flow Java / JS / C++ / C# … May be simulated with channels No external libraries
76. Summary / Will have reactive DB access, soon / Spring Data drives R2DBC / It is time to try R2DBC! / Reactive vs Fibers: friends or foes?
77. Q&A Thank you! /aigor /siromaha /ihor.lozinsky