Performance Tuning

Tracking down performance regressions when developing Spring Boot can be challenging. This page documents some techniques that we occasionally use.

Test applications

The spring-boot-sample-tomcat and spring-boot-sample-actuator-ui projects are good first candidates. There’s also spring-boot-startup-bench. Changing the main method to call .close() helps with repeated launching:

public static void main(String[] args) throws Exception {
   SpringApplication.run(SampleTomcatApplication.class, args).close();
}

GC Pauses

Startup speed can suffer if too many GC pauses happen. This can be a pain to track down because a relatively small change might suddenly push the memory limits.

Printing GC can be a useful way to see what’s changed between versions:

java -XX:+PrintGC -XX:+PrintGCTimeStamps -XX:+PrintGCDateStamps -jar target/*.jar | grep GC

Relative logging

logging.pattern.console=%8r %d{yyyy-MM-dd HH:mm:ss.SSS} %5p --- [%15.15t] %-40.40logger{39} : %m%n%wEx