Speed up Spring Boot startup time

问题:

I have a Spring Boot application. I've added a lot of dependencies (unfortunately, looks I need all of them) and the startup time went up quite a lot. Just doing a SpringApplication.run(source, args) takes 10 seconds.

While that might not be much compared to what are "used" to, I'm unhappy that it takes that much, mostly because it breaks the development flow. The application itself is rather small at this point, so I assume most of the time is related to the added dependencies, not the app classes themselves.

I assume the issue is classpath scanning, but I am not sure how to:

• Confirm that is the issue (i.e. how to "debug" Spring Boot)
• If it really is the cause, how can I limit it, so it gets faster? For example, if I know that some dependency or package does not contain anything that Spring should be scanning, is there a way to limit that?

I assume this:

• https://jira.spring.io/browse/SPR-8767

would speed up things, but it's not even triaged at this point. I see some other efforts in Spring Boot itself, e.g.:

• https://github.com/spring-projects/spring-boot/issues/1610

but this looks Tomcat-specific.

This article:

• http://www.nurkiewicz.com/2010/12/speeding-up-spring-integration-tests.html

although aimed at integration tests, suggests using lazy-init=true, however I do not know how to apply this to all beans in Spring Boot using Java configuration - any pointers here?

Any (other) suggestions would be welcome.

回答1:

Spring Boot does a lot of auto-configuration that may not be needed. So you may want to narrow down only auto-configuration that is needed for your app. To see full list of auto-configuration included, just run logging of org.springframework.boot.autoconfigure in DEBUG mode (logging.level.org.springframework.boot.autoconfigure=DEBUG in application.properties). Another option is to run spring boot application with --debug option: java -jar myproject-0.0.1-SNAPSHOT.jar --debug

There would be something like this in output:

=========================
AUTO-CONFIGURATION REPORT
=========================

Inspect this list and include only autoconfigurations you need:

@Configuration
@Import({
        DispatcherServletAutoConfiguration.class,
        EmbeddedServletContainerAutoConfiguration.class,
        ErrorMvcAutoConfiguration.class,
        HttpEncodingAutoConfiguration.class,
        HttpMessageConvertersAutoConfiguration.class,
        JacksonAutoConfiguration.class,
        ServerPropertiesAutoConfiguration.class,
        PropertyPlaceholderAutoConfiguration.class,
        ThymeleafAutoConfiguration.class,
        WebMvcAutoConfiguration.class,
        WebSocketAutoConfiguration.class,
})
public class SampleWebUiApplication {

Code was copied from this blog post.

回答2:

The most voted answer so far is not wrong, but it doesn't go into the depth I like to see and provides no scientific evidence. The Spring Boot team went through an exercise for reducing startup time for Boot 2.0, and ticket 11226 contains a lot of useful information. There is also a ticket 7939 open to adding timing information to condition evaluation, but it doesn't seem to have a specific ETA.

The most useful, and methodical approach for debugging Boot startup has been done by Dave Syer. https://github.com/dsyer/spring-boot-startup-bench

I had a similar use case as well, so I took Dave's approach of micro-benchmarking with JMH and ran with it. The result is the boot-benchmark project. I designed it such that it can be used to measure startup time for any Spring Boot application, using the executable jar produced by bootJar (previously called bootRepackage in Boot 1.5) Gradle task. Feel free to use it and provide feedback.

My findings are as follows:

1. CPU matters. A lot.
2. Starting the JVM with -Xverify:none helps significantly.
3. Excluding unnecessary autoconfigurations helps.
4. Dave recommended JVM argument -XX:TieredStopAtLevel=1, but my tests didn't show significant improvement with that. Also, -XX:TieredStopAtLevel=1 would probably slow down your first request.
5. There have been reports of hostname resolution being slow, but I didn't find it to be a problem for the apps I tested.

回答3:

As described in this question/answer, I think the best approach is to instead of adding only those you think you need, exclude the dependencies you know you don't need.

See: Minimise Spring Boot Startup Time

In summary:

You can see what is going on under the covers and enable debug logging as simple as specifying --debug when starting the application from the command-line. You can also specify debug=true in your application.properties.

Also, you can set the logging level in application.properties as simple as:

logging.level.org.springframework.web: DEBUG logging.level.org.hibernate: ERROR

If you detect an auto-configured module you don't want, it can be disabled. The docs for this can be found here: http://docs.spring.io/spring-boot/docs/current-SNAPSHOT/reference/htmlsingle/#using-boot-disabling-specific-auto-configuration

An example would look like:

@Configuration
@EnableAutoConfiguration(exclude={DataSourceAutoConfiguration.class})
public class MyConfiguration {
}

回答4:

If you're trying to optimize development turn-around for manual testing, I strongly recommend the use of devtools.

Applications that use spring-boot-devtools will automatically restart whenever files on the classpath change.

Just recompile -- and the server will restart itself (for Groovy you only need to update the source file). if you're using an IDE (e.g. 'vscode'), it may automatically compile your java files, so just saving a java file can initiate a server restart, indirectly -- and Java becomes just as seamless as Groovy in this regard.

The beauty of this approach is that the incremental restart short-circuits some of the from-scratch startup steps -- so your service will be back up and running much more quickly!

---

Unfortunately, this doesn't help with startup times for deployment or automated unit testing.

回答5:

I find it strange nobody suggested these optimizations before. Here're some general tips on optimizing project build and startup when developing:

• exclude development directories from antivirus scanner:
  • project directory
  • build output directory (if it's outside of project directory)
  • IDE indices directory (e.g. ~/.IntelliJIdea2018.3)
  • deployment directory (webapps in Tomcat)
• upgrade hardware. use faster CPU and RAM, better internet connection (for downloading dependencies) and database connection, switch to SSD. video card doesn't matter.

回答6:

My finding is that Hibernate adds significant time to application startup. Disabling L2 cache and database initialization results in faster Spring Boot app startup. Leave cache ON for production and disable it for your development environment.

application.yml:

spring:
  jpa:
    generate-ddl: false
    hibernate:
      ddl-auto: none
    properties:
      hibernate:
        cache:
          use_second_level_cache: false
          use_query_cache: false

Test results:

1. L2 cache is ON and ddl-auto: update

   INFO 5024 --- [restartedMain] o.s.web.context.ContextLoader : Root WebApplicationContext: initialization completed in 23331 ms
   INFO 5024 --- [restartedMain] b.n.spring.Application : Started Application in 54.251 seconds (JVM running for 63.766)
   

2. L2 cache is OFF and ddl-auto: none

   INFO 10288 --- [restartedMain] o.s.web.context.ContextLoader : Root WebApplicationContext: initialization completed in 9863 ms
   INFO 10288 --- [restartedMain] b.n.spring.Application : Started Application in 32.058 seconds (JVM running for 37.625)
   

Now I wonder what will I do with all this free time

回答7:

To me it sounds like you're using a wrong configuration setting. Start by checking myContainer and possible conflicts. To determine who is using the most resources you have to check the memory maps (see the amount of data!) for each dependency at a time - and that takes plenty of time, as well... (and SUDO privileges). By the way: are you usually testing the code against the dependencies?