Lean spring-boot Application

src: Lean Spring Boot Application - 2023-02-16

Abstract

Some tips and tricks to improve Spring Boot startup time:

• use Packeto Buildpack to build your Docker images
  • more secure
  • more optimized
• can use spring-context-indexer to generate a META-INF/spring.components file that included in the jar file in order to accelerate startup time
• lazy spring beans can be activated globally with -e spring.main.lazy-initialization=true
  • pros
    • faster startup time
    • application startup is a CPU intensive tasks, spreading the load over time
  • cons
    • initial requests may take more time
    • class loading issues and missconfiguration unnoticed at startup
    • beans creation erros only be found at the time of loading the bean
• tiered compilation is enabled by default since Java 8. Unless explicitly specified, the JVM decides with JIT compiler to use based on our CPU. For multi-core processors or 64-bit VMs, the JVM wil select C2.
  • In order to disable C2 and only use C1 compiler with no profiling overhead, we can apply the -XX:TieredStopAtLevel=1 parameter
  • -e "JAVA_TOOL_OPTIONS=-XX:TieredStopAtLevel=1"
  • it will slow down the JIT later at the expense of the saved startuptime
• no spring boot actuator to accelerate startup time
• fixing spring boot config location with -e spring.config.location=classpath:application.properties to gain a bit of time
• dependency cleanup using decpclean-maven-plugin to detect and remove all unused dependencies declared in the pom.xml of a project:

< plugin>
  <groupId>se.kth.castor</groupId>
  <artifactId>depclean-maven-plugin</artifactId>
  <version>2.0.6</version>
  < executions>
    < execution>
      <goals><goal>depclean</goal></goals>
    </execution>
  </executions>
</plugin>

• using jlink, that assembles and optimizes a set of modules and their dependencies into a custom runtime image for your application, to reduce image size:

< plugin>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-maven-plugin</artifactId>
  < configuration>
    < image>
      < env>
        <BP_JVM_JLINK_ENABLED>true</BP_JVM_JLINK_ENABLED>
        <BP_JVM_JLINK_ARGS>...</BP_JVM_JLINK_ARGS>
      </env>
    </image>
  </configuration>
</plugin>

• native build with GraalVM
  • long build time
  • result can be different from what you run in your IDE
• CRaC - OpenJDK (Checkpoint and Restart in Java): feature that allows to checkpoint the state of a Java application and restart it from the checkpointed state ⇒ application starts within milliseconds!
  • still experimental
  • does not work with spring boot 3
  • does not work in Docker containers
  • does not work on Windows or on macOS
• bytecode obfuscating and shrinking can be used to reduce the size of the application
  • Use Proguard and YGuard (tools used for Android)