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Java Module System
How to decrease your application footprint
Leonardo Zanivan - Crossover Rodrigo Cândido da Silva - Integritas
Java Module System How to decrease your application footprint - - PowerPoint PPT Presentation
Java Module System How to decrease your application footprint - - PowerPoint PPT Presentation
Java Module System How to decrease your application footprint Leonardo Zanivan - Crossover Rodrigo Cndido da Silva - Integritas Java 9 Modules System Previous Module System Classpath After Module System Classpath JDK 9+ Spring Modules jlink
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Java 9 Modules System
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Previous Module System Classpath
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After Module System Classpath
JDK 9+
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Spring Modules
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jlink exec
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- Spring Boot 2 sample application with REST MVC & JPA
1. Create module-info.java with all the required imports 2. Update third party libs with JDK 9/10 fixes 3. Add new Maven plugin to copy dependencies 4. No Java code change was required
Migrating Spring PetClinic to Java 9 Modules
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- Application can still run with explicit classpath after migration
- Use --upgrade-module-path to override problematic modules
- You will find that third party libs are not ready to use modules
Lessons Learned
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- Automatic modules can cause issues (naming conflicts, JLink)
○ e.g: JLink was used to create a minimal JRE manually
- Third party libs may require you to open some packages
○ e.g: Hibernate JPA, Spring
- Hello World always work!
Lessons Learned
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JDK 10 Highlights
Docker awareness
JDK-8146115 enhancement JDK-8186309 enhancement JDK-8179498 enhancement
Can extract container-specific information about number
- f CPUs (automatically)
Can extract container-specific information about allocated memory (automatically) Attaching to namespace issue(s) have been resolved!
host PID ⇒ container PID
New JVM flags for Docker support:
- XX:UseContainerSupport
(default)
- XX:ActiveProcessorCount
- XX:InitialRAMPercentage
- XX:MaxRAMPercentage
- XX:MinRAMPercentage
Support for Linux only
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JDK 10 Highlights
Reduce resource footprint when multiple JVMs were running on the same physical machine
JEP 310: Application Class-Data Sharing
Pre-Java 10, use of CDS had been restricted to the bootstrap class loader only Improve startup time
- f application
Processes/applications can sharing common class metadata (class-data), from a shared archive (CDS archive)
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- java.xml.ws (JAX-WS)
- java.xml.bind (JAXB)
- java.activation (JAF)
- java.xml.ws.annotation (JSR 250)
- java.corba (CORBA)
- java.transaction (JTA)
- java.se.ee (Aggregator module)
- jdk.xml.ws (Tools for JAX-WS)
- jdk.xml.bind (Tools for JAXB)
JDK 11 Changes
JEP 320: Remove Java EE and CORBA Modules
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Eclipse OpenJ9
- TL;DR; 2x smaller memory
footprint and starts 2x faster than HotSpot.
- Experimental; AdoptOpenJDK
builds are available. https://adoptopenjdk.net
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github.com/panga/qcon2018-java9modules
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Note: JDK 10 Alpine was built from source: https://hub.docker.com/r/panga/openjdk10/
JDK 10 Minimal JRE + Module Application < 100mb
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Note: Best case scenario during my tests. Limit: 2 cpus, 1g memory, JVM_OPTS= Xmx512m
JDK 10 Modules starts 2x faster on Docker
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Note: Best case scenario during my tests. JMeter test plan was used to load application.
JDK 10 Modules has 2x lower footprint on Startup!
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JDK 10 Modules has 2x lower footprint after Load!
Note: Best case scenario during my tests. JMeter test plan was used to load application.
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github.com/panga/spring-petclinic-java9modules
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