Add cats-effect instrumentation #13576
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| import cats.effect.IOLocal; | ||
| import io.opentelemetry.javaagent.instrumentation.opentelemetryapi.context.AgentContextStorage; | ||
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| public class IoLocalContextSingleton { |
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It must be defined in a common package so we can lately reuse it to instrument otel4s.
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Here is a prototype: iRevive@b2f6501
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Some tests have failed with the following error: I assume some VMs aren't happy with the body modification of IO? |
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| @Advice.OnMethodEnter(suppress = Throwable.class) | ||
| public static void onEnter() { | ||
| FiberLocalContextHelper.initialize( |
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What if you have deployed 2 wars on tomcat that use this library, won't this break? Messing with the context storage is unusual, my hunch is that this is not a good idea. Typically such instrumentations restore the otel context when fiber starts running on a thread and save the context when it stops using the thread.
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That's a valid concern indeed.
deployed 2 wars on tomcat that use this library
If I understand correctly, each deployment (app) will have its own classloader, but the bootstrap will still be shared.
If that's the case, my implementation won't work, I'm afraid.
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Suppose I don't find a proper way to make the instrumentation work. Can I distribute the current implementation as a third-party extension? Can the extension have access to the bootstrap loader?
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Can the extension have access to the bootstrap loader?
Not directly, but you could try using byte-buddy to define the class you need in boot loader or you could experiment with Instrumentation.appendToBootstrapClassLoaderSearch.
Closes #10599.
Hey folks.
Cats Effect is a high-performance, asynchronous, composable framework for building real-world applications in a purely functional style within the Typelevel ecosystem.
How the instrumentation works
Cats Effect has its context propagation mechanism known as IOLocal. 3.6.0 release provides a way to represent IOLocal as a
ThreadLocal, which creates an opportunity to manipulate the context from the outside.IORuntimeand stores aThreadLocalrepresentation of theIOLocal[Context]in the bootstrap classloader, so the agent and application both access the same instanceContextStoragewrapper (for the agent context storage). This wrapper usesFiberLocalContextHelperto retrieve the fiber's current context (if available)IOFiber's constructor and starts the fiber with the currently available context