This little app can create the CDS archive for an app and produce a report of how it went. It can also read the JVM logs and produce a report about class loading.
You can use the tool to create the CDS archive for you. Based on the working directory, it will detect a Spring Boot exploded structure.
$ ./cds-log-parser.jar --target=/usr/local/my-app --mode=create
Alternatively, you can specify the jar file to use using the jar argument:
$ ./cds-log-parser.jar --target=/usr/local --jar=my-app.jar --mode=create
This should create a application.jsa in the working directory and a report about classes that have been skipped and why.
It also provides hints of how to use the archive.
If you want to create the archive yourself, you need to specify a flag when starting the app:
$ java -XX:ArchiveClassesAtExit=application.jsa -jar my-app.jar
Parsing Class Loading logs is a good way to figure out how effective the CDS cache is.
Without any extra option, the tool looks for a file named cds.log in the working directory.
You can produce the logs on any application as follows:
$ java -Xlog:class+load:file=cds.log:tags -XX:SharedArchiveFile=application.jsa -jar my-app.jar
To run a report, specify the working directory where the cds.log file is located:
$ ./cds-log-parser.jar --target=/usr/local/my-app
This is the report of a Spring Boot app using Hibernate with only the default class archive (i.e. the JDK):
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Class Loading Report:
15743 classes and JDK proxies loaded
1228 ( 7,80%) from cache
14515 (92,20%) from classpath
Categories:
Lambdas 1709 (10,86%): 2,28% from cache
Proxies 174 ( 1,11%): 0,00% from cache
Classes 13862 (88,05%): 8,58% from cache
Top 10 locations from classpath:
3021 BOOT-INF/lib/hibernate-core-6.3.1.Final.jar
892 jrt:/java.base
799 BOOT-INF/lib/byte-buddy-1.14.9.jar
564 BOOT-INF/lib/h2-2.2.224.jar
560 BOOT-INF/lib/spring-boot-3.2.0-SNAPSHOT.jar
508 BOOT-INF/lib/spring-core-6.1.0-RC2.jar
439 BOOT-INF/lib/hibernate-validator-8.0.1.Final.jar
428 BOOT-INF/lib/spring-boot-autoconfigure-3.2.0-SNAPSHOT.jar
353 BOOT-INF/lib/spring-context-6.1.0-RC2.jar
327 __JVM_LookupDefineClass__
Top 10 packages:
5054 org.springframework (0,00% from cache)
3780 org.hibernate (0,00% from cache)
810 net.bytebuddy (0,00% from cache)
795 java.lang (35,97% from cache)
733 java.util (56,48% from cache)
575 org.h2 (0,00% from cache)
523 com.fasterxml (0,00% from cache)
323 org.aspectj (0,00% from cache)
310 org.apache (0,00% from cache)
306 jdk.internal (58,82% from cache)
--------------------------------------------------------------------------And the report for the same app with a dedicated archive, created with the -XX:ArchiveClassesAtExit=application.jsa:
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Class Loading Report:
15909 classes and JDK proxies loaded
13140 (82,59%) from cache
2769 (17,41%) from classpath
Categories:
Lambdas 1736 (10,91%): 11,23% from cache
Proxies 175 ( 1,10%): 56,57% from cache
Classes 14000 (88,00%): 91,76% from cache
Top 10 locations from classpath:
759 BOOT-INF/lib/byte-buddy-1.14.9.jar
347 __JVM_LookupDefineClass__
75 __dynamic_proxy__
69 org.springframework.boot.autoconfigure.web.embedded.TomcatWebServerFactoryCustomizer
39
31 org.springframework.boot.autoconfigure.web.servlet.ServletWebServerFactoryCustomizer
19 org.springframework.data.mapping.model.Property
16 org.springframework.core.io.support.SpringFactoriesLoader
16 org.springframework.data.mapping.model.AnnotationBasedPersistentProperty
16 org.springframework.boot.autoconfigure.web.WebProperties
Top 10 packages:
5078 org.springframework (77,37% from cache)
3776 org.hibernate (92,77% from cache)
847 java.lang (60,45% from cache)
810 net.bytebuddy (4,94% from cache)
737 java.util (98,78% from cache)
575 org.h2 (98,09% from cache)
523 com.fasterxml (95,98% from cache)
323 org.aspectj (100,00% from cache)
322 jdk.internal (99,07% from cache)
310 org.apache (97,74% from cache)
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