DeveloperWeek Europe 2023 - Revolutionize Java DB AppDev with Reactive Streams and Virtual Threads

1. Revolutionize Java Database App
Development with Reactive Streams and
Virtual Threads
DeveloperWeek Europe
Juarez Barbosa Junior - @juarezjunior
April 2023
Copyright © 2022, Oracle and/or its affiliates

2. Agenda
• Java App Dev with Oracle Database
• Support for the Latest Java Versions
• Overview of Oracle DB Access with Java
• Oracle JDBC – Sync and Async
• Classic Java Platform Threads
• Project Loom – Virtual Threads
• Virtual Threads - JEP 425 (Preview API)
• Demo # 1: Virtual vs Platform Threads
• Reactive JDBC - Synchronous vs Asynchronous JDBC
• Reactive Streams Ingestion (RSI)
• Demo # 2: Reactive Streams Ingestion (RSI)
• From Sync to Reactive JDBC: Oracle R2DBC
• Demo # 3: Oracle R2DBC
• Live Labs/Free Oracle Cloud Account/Oracle ACE Program
Copyright © 2022, Oracle and/or its affiliates

3. Copyright © 2022, Oracle and/or its affiliates
Java App Dev with Oracle Database

4. Copyright © 2022, Oracle and/or its affiliates
Support for the Latest Java Versions
• Java 11 - native support, compiled with it
• Java 17 - certified
• JDBC Standards - 4.2 and 4.3
• JMS 1.1 - latest is 2.0
• GraalVM - native image instrumentation
• Reactive Streams - Java Flow API support
• Project Loom - Virtual Threads support
• Data access is critical in mission-critical apps

5. Copyright © 2022, Oracle and/or its affiliates
Overview of Oracle DB Access with Java
User
Java
Code
JDBC
Reactive
Extension Standard
JDBC API
R2DBC
+
3rd party
Reactive
Streams
Libraries
Async call with non-blocking
backpressure
operators (map, reduce, filters),
concurrency modeling,
monitoring, tracing
Implements Java SE
reactive stream
interface (Flow)
Full Reactive
Streams
Sync/blocking JDBC calls
Java
Business
Logic
User Java code
Oracle
Database
Oracle JDBC
driver
VTs/lightweight JDBC calls

6. Copyright © 2022, Oracle and/or its affiliates
Oracle JDBC – Async and Sync
⚫ Reactive Programming
− Asynchronous database access with non-blocking network I/O
− Oracle R2DBC + Oracle JDBC Reactive Extensions + Oracle Reactive Streams Ingestion
− Application call stack must be fully asynchronous
− Libraries are here to support it: Reactor, RxJava, Akka, Vert.x
⚫ Project Loom/Virtual Threads
− Synchronous database access with lightweight threads
− Standard JDBC + Virtual Threads
− Client application call stack may use conventional (synchronous) code
− Libraries must be compatible with Virtual Threads
− Oracle instrumented the Oracle JDBC 21c driver to support Virtual Threads

7. Copyright © 2022, Oracle and/or its affiliates
Classic Java Platform Threads
⚫ Blocking Threads
⚫ A JDBC call blocks a thread for 100’s of milliseconds (thread-per-request style)
⚫ Thread count increases linearly with the number of JDBC calls
⚫ Performance degrades as the number of threads increases
⚫ 1 MB of stack memory per thread
⚫ Scheduling many platform threads is expensive
⚫ Preemptive scheduling vs time-slicing

8. Copyright © 2022, Oracle and/or its affiliates
Virtual Threads - JEP 425, 436, 444
⚫ Virtual Threads – JEP (JDK Enhancement Proposals)
⚫ Lightweight threads that dramatically reduce the effort of writing, maintaining, and
observing high-throughput concurrent applications
⚫ Enable applications written in the simple thread-per-request style to scale with near-
optimal hardware utilization
⚫ Enable existing code that uses the java.lang.Thread API to adopt virtual threads with
minimal change
⚫ Enable easy troubleshooting, debugging, and profiling of virtual threads with existing
JDK tools
⚫ Do not remove the traditional implementation of threads
⚫ Do not alter the basic concurrency model of Java

9. Copyright © 2022, Oracle and/or its affiliates
Demo # 1: Virtual vs Platform Threads
⚫ Virtual Threads versus Platform Threads
⚫ JEP 425 Virtual Threads (Preview)
⚫ JEP 436 (Second Preview)
⚫ JEP 444 (Targeted – JDK 21)
⚫ Runs on Java 19, 20, 21
⚫ javac --release 19 --enable-preview
⚫ java --enable-preview
⚫ Comparison of OS resources consumption (Threads only + JDBC)
⚫ Oracle JDBC Driver 21c instrumented to support Virtual Threads
⚫ API is Oracle JDBC with the Java SE library (Executor, ThreadFactory)

10. Copyright © 2022, Oracle and/or its affiliates
Reactive JDBC - Synchronous vs Asynchronous JDBC
Setup
Blocking
Handle Result
Setup
Non-Blocking
Handle Result
Synchronous JDBC Setup
Blocking
Handle Result
Setup
Non-Blocking
Handle Result
Setup
Non-Blocking
Handle Result
Reactive JDBC
Database
Setup
Blocking
Handle Result
Database

11. Copyright © 2022, Oracle and/or its affiliates
Reactive Streams Ingestion (RSI)
⚫ Java Library for Reactive Streams Ingestion
⚫ Streaming capability: Ingest data in an unblocking, and
reactive way from a large group of clients
⚫ Group records through RAC (Real App Clusters),
and Shard affinity using native UCP (Universal Connection
Pool)
⚫ Optimize CPU allocation while decoupling record
Processing from I/O
⚫ Fastest insert method for the Oracle Database through
Direct Path Insert, bypassing SQL and writing directly into the DB files

12. Copyright © 2022, Oracle and/or its affiliates
Demo # 2: Reactive Streams Ingestion (RSI)
Container
Pipelines,
Jenkins, etc.
Build
Test
Push
Push Docker
images to
Registry
Cloud
Infrastructur
e Registry
Container
Engine for
Kubernetes
Pull images
from Registry
Deploy
images to
production
Kubernetes
worker nodes
Containers
running
microservices
deployed over
Kubernetes
ORACLE CLOUD INFRASTRUCTURE
ATP, ADW, ATP-D,
AFDW-D
Memoptimized
Rowstore
RSI Runtime: Non-
blocking, optimized library
for streaming data
through Direct Path, Shard
& RAC/FAN support.
HTTP / REST Engine over
Helidon
Define build
for CI/CD
toolchain
gRPC / AMQP / MQTT
Engines
Microservices
Files / Logs
IoT
Devices
/
Apps
cv
MQTT
gRPC
AMQP
HTTP / REST
JDBC
Direct Path
INSERT
Record
Streaming
over
multiple
protocols.

13. Copyright © 2022, Oracle and/or its affiliates
From Sync to Reactive JDBC: Oracle R2DBC
static String queryJdbc(java.sql.Connection connection) throws
SQLException {
try (java.sql.Statement statement = connection.createStatement()) {
ResultSet resultSet =
statement.executeQuery("SELECT * FROM CUSTOMERS");
if (resultSet.next())
return resultSet.getString(1);
else
throw new NoSuchElementException("Query returned zero rows");
}
}
static Publisher<String> queryR2dbc(io.r2dbc.spi.Connection
connection) {
return Flux.from(connection.createStatement(
"SELECT * FROM CUSTOMERS")
.execute())
.flatMap(result ->
result.map(row -> row.get(0, String.class)))
.switchIfEmpty(Flux.error(
new NoSuchElementException("Query returned zero rows")));
}

14. Copyright © 2022, Oracle and/or its affiliates
Oracle R2DBC
⚫ Oracle Reactive Relational Database Connectivity (R2DBC)
⚫ Oracle R2DBC Driver is a Java library that supports reactive
Programming with Oracle Database
⚫ It implements the R2DBC Service Provider Interface (SPI) as
specified by the Reactive Relational Database Connectivity (R2DBC)
⚫ The R2DBC SPI exposes Reactive Streams as an abstraction for
Remote database operations
⚫ The sample code uses Project Reactor. It could use RxJava, Akka,
or any RS library
⚫ Runs on Java 11+

15. Virtual Threads or
Reactive?
• Oracle JDBC supports both!
• Want Virtual Threads?
• Oracle JDBC has been “Virtual Thread
Compatible” since 21.1.0.0
• Want Reactive?
• Oracle R2DBC 1.0.0 is available now
• Consume Flow interfaces directly from
Oracle JDBC’s Reactive Extensions
Copyright © 2022, Oracle and/or its affiliates

16. Virtual Threads or Reactive?
• Benefits of Virtual Threads:
• Easier to read and write
• Easier to debug
• Integration with JDK tools
• Do not alter the basic concurrency model of Java
• Limitations of Virtual Threads:
• Some libraries are not compatible
Copyright © 2022, Oracle and/or its affiliates
Benefits of Reactive:
• Reactive Libraries (Reactor, RxJava, Akka, Vert.x)
• Stream-like API with a functional style
• Low-level concurrency is handled for you
(locks, atomics, queues).
Limitations of Reactive:
• Steep learning curve
• Harder to read and write
• Harder to debug

17. Copyright © 2022, Oracle and/or its affiliates
References
• Project Loom / Virtual Threads
• Loom - https://openjdk.org/projects/loom/
• JEP 444 Virtual Threads (Targeted) - https://openjdk.org/jeps/444
• Introduction to Oracle JDBC 21c Driver Support for Virtual Threads - https://bit.ly/3UlNJWP
• Reactive Streams Ingestion Library
• Getting Started with the Java library for Reactive Streams Ingestion (RSI) -
https://bit.ly/3rEiRnC
• High-throughput stream processing with the Java Library for Reactive Streams Ingestion (RSI),
Virtual Threads, and the Oracle ATP Database - https://bit.ly/3rATCTd
• RSI - https://docs.oracle.com/en/database/oracle/
• R2DBC
• Oracle R2DBC Driver – https://github.com/oracle/oracle-r2dbc
• Develop Java applications with Oracle Database
• JDBC – https://www.oracle.com/database/technologies/appdev/jdbc.html

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20. 3 membership tiers
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21. About me
• Juarez Barbosa Junior - @juarezjunior
• Senior Principal Java Developer Evangelist
• 27 years of experience
• SW Engineering, Developer Relations
• Microsoft, Oracle, IBM, Nokia, Unisys, Accenture, and a
few startups
• Microsoft Azure Developer Relations Lead
• IBM Watson Tech Evangelist & Cloud Rockstar
• IBM Mobile Tech Evangelist & Global Thought Leader
• Nokia Developers Global Champion
• Lead Software/DevOps Architect
• Expertise
• Java, Cloud, DevOps, Cloud-native, Blockchain
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22. Thank you!
22
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