JaCoCo 0.8.13 fails to instrument DefaultSsmClient (ClassTooLargeException)

[jpalomaki]

Describe the bug

I see this error when running a Maven build with the JaCoCo code coverage plugin, Java 21, and AWS SDK v2 version 2.31.76, with the AWS SDK v2 SSM dependency in classpath.

java.lang.instrument.IllegalClassFormatException: Error while instrumenting software/amazon/awssdk/services/ssm/DefaultSsmClient with JaCoCo 0.8.13.202504020838/78d5eff`

Regression Issue

• Select this option if this issue appears to be a regression.

Expected Behavior

No error emitted

Current Behavior

Instrumentation error emitted in maven build, see https://github.com/jpalomaki/aws-sdk-java-v2-ssm-jacoco-sscce/actions/runs/16073837387/job/45364298935#step:4:41

Reproduction Steps

https://github.com/jpalomaki/aws-sdk-java-v2-ssm-jacoco-sscce

Possible Solution

Can the generated code be modularized better (to not create very large classes)?

Additional Information/Context

The issue can be worked around by adding an exclusion to the JaCoCo plugin like so:

<configuration>
    <excludes>
        <exclude>software/amazon/awssdk/services/ssm/DefaultSsmClient</exclude>
    </excludes>
</configuration>

However, I submitted this issue because I felt that it might be better to optimize the generated code, if possible.

AWS Java SDK version used

2.31.76

JDK version used

openjdk version "21.0.5" 2024-10-15 LTS (corretto)

Operating System and version

Ubuntu 24.04 and macOS 15.5

[debora-ito]

@jpalomaki do you have more details on the IllegalClassFormatException that JaCoCo is throwing?
Like, is there more in the stacktrace?
Or maybe JaCoCo outputs a report?

[jpalomaki]

@jpalomaki do you have more details on the IllegalClassFormatException that JaCoCo is throwing? Like, is there more in the stacktrace? Or maybe JaCoCo outputs a report?

Not really, instrumentation fails with ClassTooLargeException. You can look at the provided SSCCE to see the full stack trace, and to test it yourself.

If I decompile the generated DefaultSsmClient class in my IDE, I see that it is approx. 75000 lines of code. In comparison, e.g. DefaultS3Client is only 13000 LOC.

FWIW, this jacoco issue seems to describe a similar problem (but is not related to AWS SDK).

[debora-ito]

Copying the relevant stacktrace here:

Caused by: org.jacoco.agent.rt.internal_0e20598.asm.ClassTooLargeException: Class too large: software/amazon/awssdk/services/ssm/DefaultSsmClient
	at org.jacoco.agent.rt.internal_0e20598.asm.ClassWriter.toByteArray(ClassWriter.java:616)
	at org.jacoco.agent.rt.internal_0e20598.core.instr.Instrumenter.instrument(Instrumenter.java:92)
	at org.jacoco.agent.rt.internal_0e20598.core.instr.Instrumenter.instrument(Instrumenter.java:109)
	... 92 more

I see. Thank you for bringing this up. We have other reported impacts of service clients getting too big in size. To fix this, we need to change the source model in a way that works for all language SDKs, so it'll require some careful planning.

Can you remove transitive dependencies from the code coverage tests? You'll run into the same issue if you use other large clients like ec2 or sagemaker.