Consolidate otel.exporter.jar and otel.initializer.jar into single feature otel.javaagent.extensions?

[trask]

otel.javaagent.extensions could be a single jar file, a list of jar files, or a folder with jar files

It would behave same as otel.initializer.jar where those jar files just get added to AgentClassLoader (or even better follow @jsuereth's proposal of loading them in a mostly-isolated child of AgentClassLoader).

And all of the normal autoconfigure SPIs can be used to add exporters, span processors, propagators.

I like the runtime shading of the existing ExporterClassLoader, but would probably vote to do away with it due to startup overhead, and make sure we document how to shade properly using both gradle and maven.

[trask]

Adding note here about benefits of runtime shading: #2570 (reply in thread)

[trask]

Also note that as part of this we will drop io.opentelemetry.javaagent.tooling.exporter.SpanExporterFactory, and only support io.opentelemetry.sdk.autoconfigure.spi.ConfigurableSpanExporterProvider from io.opentelemetry:opentelemetry-sdk-extension-autoconfigure

[tobias-]

Nit: They're otel.javaagent.experimental.exporter.jar and otel.javaagent.experimental.initializer.jar

Doh. Issue predates the PR

[sumitm-iiit]

@trask : I was trying out "otel.javaagent.experimental.initializer.jar" system property. It seems to work when i provide the path of the exact jar file. But when i provide the path of a folder that contains multiple jars, it does not seem to load those jars. Is that something expected as based on your description above it seems its expected to work with folders containing multiple jars as well.

[trask]

when i provide the path of a folder that contains multiple jars, it does not seem to load those jars

ya, this has not been implemented yet, but is planned

[sumitm-iiit]

@trask : Any idea by when it would be implemented.

[iNikem]

@trask : Any idea by when it would be implemented.

During the June

[trask]

this is done! please see https://github.com/open-telemetry/opentelemetry-java-instrumentation/tree/main/examples/extension#introduction

[sumitm-iiit]

@trask : Thanks for notifying.