Andersen_Revolutionize Java DB AppDev with Reactive Streams and Virtual Threads.pdf

Revolutionize Java Database Application
Development with Reactive Streams and
Virtual Threads
Andersen Lab - Poland
Juarez Barbosa Junior @juarezjunior
Senior Principal Java Developer Evangelist
ORACLE
Copyright © 2024, Oracle and/or its affiliates

Juarez Barbosa Junior
Senior Principal Java Developer Evangelist @ Oracle
• Coming from Dublin, Ireland
• 28 years of experience in SW Engineering & DevRel
• Oracle, Microsoft, IBM, Nokia, Unisys, Accenture, startups
• Microsoft Azure Developer Relations Lead
• IBM Watson Tech Evangelist & Cloud Rockstar
• IBM Mobile Tech Evangelist & Global Thought Leader
• Nokia Developers Global Champion
• Java, Python, Cloud, DevOps, SRE, Cloud-native, IoT, AI, Blockchain,
Rust
• Speaker at conferences
• Oracle CloudWorld, Oracle Code, Microsoft Ignite & TechX, jPrime,
JCON, DevConf.cz, GeeCon, DevOpsDays, DeveloperWeek, DevOps
Institute, CloudLand, DWX, The Developer’s Conference (TDC),
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Science Summit, OpenSourceNorth, WeAreDevelopers, Global
Software Architecture Summit, JavaCro, JUGs, OUGs, GDGs,
meetups, hackathons, and customer engagements.
@juarezjunior
@juarezjunior

Agenda
• Java App Dev with the Oracle Database
• Oracle JDBC - 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 - JEPs 425, 436, 444
• 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 with Project Reactor
• Live Labs/Free Oracle Cloud Account/Oracle ACE Program

Java App
Dev with
Oracle
Database

Overview of Oracle DB Access with Java

Oracle JDBC - Support for the Latest Java Versions
• Java 11 - native support, compiled with it
• Java 17 - certified
• JDBC Standards - 4.2 and 4.3
• GraalVM - native image instrumentation
• Reactive Streams - Java Flow API support
• Project Loom - Virtual Threads support
• Data access is crucial in mission-critical apps

Oracle JDBC –
Async and Sync
• Project Loom - Virtual Threads
• Synchronous database access with lightweight threads
• Standard JDBC + Virtual Threads
• Client application call stack may use blocking, synchronous code
• Libraries must be compatible with Virtual Threads
• Oracle instrumented the Oracle JDBC driver to support Virtual Threads
• Reactive Programming
• Asynchronous database access with non-blocking network I/O
• Oracle Reactive Streams Ingestion + Oracle R2DBC + Oracle JDBC Reactive Extensions
(Flow)
• Libraries are available: Reactor, RxJava, Akka, Vert.x

Classic Java
Platform Threads
• Database access with blocking threads
• A JDBC call blocks a thread for 100s 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 typically
• Scheduling many platform threads is expensive
• Preemptive scheduling vs time-slicing

Virtual Threads - JEPs 425, 436, 444
• Virtual Threads – JEPs (JDK Enhancement Proposals)
• Lightweight (user mode) 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 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
• Enable existing code that uses Java threads (java.lang.Thread) to adopt virtual threads with
minimal change

• Virtual Threads – JEPs (JDK Enhancement Proposals)
• Virtual threads typically employ a small set of platform threads used as carrier threads
• Code executing in a virtual thread is not aware of the underlying carrier thread
• The currentThread() method will always return the Thread object for the virtual thread
• Virtual threads do not have a thread name by default. The getName() method returns the
empty string if a thread name is not set
• Virtual threads have a fixed thread priority that cannot be changed
• Virtual threads are daemon threads so do not prevent the shutdown sequence from
beginning (low-priority ones).

Virtual
Threads -
JEPs 425,
436, 444
• JDK Enhancement Proposals
• JEP 425: Virtual Threads (Preview)
• JEP 436: Virtual Threads (Second Preview)
• JEP 444: Virtual Threads
• java.lang.Thread
• final Boolean - isVirtual()
• static Thread.Builder.OfVirtual - ofVirtual()
• static Thread.Builder.OfPlatform - ofPlatform()
• static Thread - startVirtualThread(Runnable task)
• java.lang.Thread.Builder
• java.util.concurrent.Executors
• static ExecutorService -
newVirtualThreadPerTaskExecutor()

• java.lang.Thread.Builder
• Thread defines a
Thread.Builder API for
creating and starting
both platform and virtual
threads. The following
are examples that use
the builder:

Demo # 1: Virtual vs Platform Threads
⚫ Virtual Threads vs Platform Threads
⚫ JEP 425 Virtual Threads (Preview)
⚫ JEP 436 (Second Preview)
⚫ JEP 444 (JDK 21)
⚫ Runs on Java 19, 20, 21
⚫ javac --release 19 --enable-preview
⚫ java --enable-preview
⚫ Oracle JDBC Driver instrumented to support Virtual Threads
⚫ Verifiable comparison of OS/HW resources consumption (Platform Threads x Virtual
Threads)

Reactive JDBC - Sync vs Async 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

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

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.

Demo #2: RSI - Architecture

Demo #2: RSI - Project Structure

From Sync to Reactive JDBC: Oracle
R2DBC
• Oracle Reactive Relational Database Connectivity (R2DBC)
• Oracle R2DBC Driver is a Java library that supports reactive
programming with the Oracle Database
• It implements the R2DBC Service Provider Interface (SPI) as
specified by the Reactive Relational Database Connectivity
(R2DBC) spec
• 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 Reactive Streams library
• Runs on Java 11+
• Oracle RDBC 1.1.1 (2023), Apache v2.0, OSS
R2DBC – Reactive Relational DB Connectivity

Demo # 3: 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")));
}

Virtual Threads or
Reactive?
• Oracle JDBC supports both!
• Want Virtual Threads?
• The Oracle JDBC driver has been
“Virtual Thread Compatible” since 21c
• Want Reactive?
• Oracle R2DBC 1.1.1 is available now
• Consume Flow interfaces directly
from Oracle JDBC’s Reactive
Extensions

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
• Now available in JDK 21
• Limitations of Virtual Threads:
• Some libraries/frameworks are not
compatible yet
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

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References
• JDK 22
• The Arrival of JDK 22 - https://blogs.oracle.com/java/post/the-arrival-of-java-22
• Project Loom / Virtual Threads
• Loom - https://openjdk.org/projects/loom/
• JEP 444 Virtual Threads - https://openjdk.org/jeps/444
• Introduction to Oracle JDBC 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
• A High-Speed Data Ingestion Solution in Java Using MQTT, AMQP, and STOMP -
https://medium.com/oracledevs/a-high-speed-data-ingestion-microservice-in-java-using-mqtt-
amqp-and-stomp-135724223ae1
• R2DBC
• Oracle R2DBC Driver – https://github.com/oracle/oracle-r2dbc
• What’s in Oracle Database 23ai for Java Developers?
• https://www.oracle.com/a/tech/docs/database/whats-in-oracledb23ai-for-java-developers.pdf
• Develop Java applications with Oracle Database
• JDBC – https://www.oracle.com/database/technologies/appdev/jdbc.html

Andersen_Revolutionize Java DB AppDev with Reactive Streams and Virtual Threads.pdf

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