Can't understand what is library instrumentation

[Roiocam]

about this documrent: https://github.com/open-telemetry/opentelemetry-java-instrumentation/blob/main/docs/contributing/writing-instrumentation.md

it is clear to me that what is agent instrumentation, basically using Java instrumentation API and bytebuddy build some hack code.

like recompile JDK classess and put some mesuring code.(this is what I want to do)

but more than just hack(recompile) other library, i have my own library also need mesuring code, so i can use library instrumentation and provider interceptor using OTEL API ? and then my library user could using those API to create they own meter?

Hope it's clear what I am asking for.

Best Regard.

[Roiocam]

After re-reading the contributed markdown, I seem to understand the meaning of library instrumentation.

there is two way that create monitor for specific library:

1. for those library has callback/interceptor api: using Library instrumentation.
2. for another library without those api: use the Agent instrumentation.

For exmaple:

org.apache.kafka.clients.producer.KafkaProducer has method Future<RecordMetadata> send(ProducerRecord<K, V> record, Callback callback) .

the developer could write some mesuring code on callback.

[Roiocam]

Actually, I am implementing both library instrumentation and agent instrumentation. the project structure is like this:

javaagent ->
    src/main/java ->
        InstrumentationModuleImpl
        TypeInstrumentationImpl (inject Instrumenter API stuff, general using MyInstrumenterImpl method `start` and `end`...)
library ->
    src/main/java ->
        MyInstrumenterImpl (Instrumenter implementation)
        MyMetrics (OperationListener implementation)

I am not sure why apache-dubbo-2.7 don't need to explicitly override getAdditionalHelperClassNames on InstrumentationModule implemention. I had to do this to make Instrumentation work, and agent jar(otel.extension) need "shade" library class

[Roiocam]

What is the exact error that you're getting? Is this something connected to the OpenTelemetry code?

after override getAdditionalHelperClassNames() and boot jar with my javaagent. JVM complaints can not be found MyMetrics class.

there are two questions:

• why do I have to explicitly override getAdditionalHelperClassNames on InstrumentationModule, but apache-dubbo-2.7 not ?
• why do I have to shade library on my javaagent, but apache-dubbo-2.7 not?

I'm wondering what the magic is inside. how apache-dubbo-2.7 make ClassLoader load the helper class.

[mateuszrzeszutek]

• why do I have to shade library on my javaagent, but apache-dubbo-2.7 not?

The javaagent shading happens in the javaagent-shadowing gradle plugin from this repo -- the Dubbo instrumentation automatically includes that as a part of otel.javaagent-instrumentation plugin.

• why do I have to explicitly override getAdditionalHelperClassNames on InstrumentationModule, but apache-dubbo-2.7 not ?

The muzzle plugin is responsible for collecting the helper classes during the build time, and injecting them into the InstrumentationModule bytecode. Again, it is included by default in all javaagent instrumentation in this repo.

We're publishing gradle plugins for muzzle; but you probably won't be able to use them in a maven build.

[Roiocam]

Thanks for taking the time to answer.

seem the same as my thought, I am stuck with those Gradle plugins.

I got all answers in this discussion and I will read all documents and source code to answer my question in the future. let us get over this discussion which keeps your valuable time.

thanks again for your time.

Best Regards.

[mateuszrzeszutek]

No problem at all, you're welcome!

[Roiocam]

For anyone who has the same problem as me, HikariCP is best example in helping to understand