TypeInstrumenter match on prefix or suffix alternatives

[dmarkwat]

I'm in the process of evaluating another stack for instrumentation (pekko-grpc) and the type matching is proving somewhat challenging.

pekko-grpc uses gradle/sbt/maven plugins to generate classes, but the generated objects and classes don't share any runtime annotations or super types to hook into in the otel instrumentation. The result is resorting to matching on class name suffix...which as I discovered today isn't supported (I can imagine many reasons why).

So while I pursue upstreaming some meta types to make this simpler in the long-term (to be clear, there's no such guarantee I will get my wish), I want to ask what are the alternatives here? I've come up with a few but wondering if any of these would be suitable or if there are suggestions:

1. enumerating the classes to instrument via env var/sys props (note: I don't like this one)
2. produce manifests and stuff them into META-INF for discovery in the instrumentation for typeMatcher to then chain the classes together
   • this however would require accessing the application classpath from the typeMatcher method which a) I don't know how to do off-hands, and b) feels slightly broken? (though please correct me if I'm wrong)
3. support suffix matching on names in the instrumentations

(3) has some obvious pitfalls, (1) is pushing compile-time information up to the runtime which is counterintuitive when it's all known very literally at compile time (if instrumentation was all more granularly opt-in, I'd feel differently), and (2) may offer the best alternative I can conceive in this moment given the situation.

Thoughts? Suggestions?

[laurit]

The result is resorting to matching on class name suffix...which as I discovered today isn't supported

  public ElementMatcher<TypeDescription> typeMatcher() {
    return new ElementMatcher<TypeDescription>() {
      @Override
      public boolean matches(TypeDescription target) {
        return target.getActualName().endsWith("foo");
      }
    };
  }

[dmarkwat]

Huh...I think I see my mistake.

DEBUG net.bytebuddy.agent.builder.AgentBuilderUtil - Could not decompose matcher failSafe(try(PekkoGrpcInstrumentationModule#PowerApiHandlerInstrumentation(name(endsWith(PowerApiHandler$)))) or false)

led me to believe this wasn't working. Never mind me, this appears to be a non-issue. Sorry for the interrupt!