How do I define a receiver in the TracerProviderConfigurer

[Cavvar]

Hello everyone!

I'm writing a java-agent-extension that implements a CustomSpanProcessor that receives an OtlpGrpcSpanExporter in the constructor. The CustomSpanProcessor sets attributes during onStart() with the writable span but also has to set attributes during the onEnd() hook. Since the hook is only readable, the workaround is to convert the ReadableSpan into a writable format and then send to a custom exporter. Ideally a hook like beforeEnd() (as mentioned in Issue#1089) exists.

The configurer roughly looks like the following:

import com.google.auto.service.AutoService;
import io.opentelemetry.exporters.otlp.OtlpGrpcSpanExporter;
import io.opentelemetry.sdk.autoconfigure.spi.SdkTracerProviderConfigurer;
import io.opentelemetry.sdk.trace.SdkTracerProviderBuilder;

@AutoService(SdkTracerProviderConfigurer.class)
public class DemoSdkTracerProviderConfigurer implements SdkTracerProviderConfigurer {

    @Override
    public void configure(SdkTracerProviderBuilder sdkTracerProviderBuilder) {
        sdkTracerProviderBuilder
                .addSpanProcessor(new CustomSpanProcessor(OtlpGrpcSpanExporter.getDefault()));
    }
}

My test application is made with Quarkus. I have added the java-agent and my agent-extension into the docker image and extended the JAVA_OPTIONS parameter.

# Configure the JAVA_OPTIONS, you can add -XshowSettings:vm to also display the heap size.
ENV JAVA_OPTIONS="-javaagent:/agents/opentelemetry-javaagent-all.jar \
                  -Dotel.traces.exporter=otlp \
                  -Dotel.exporter.otlp.endpoint=http://jaeger:14250 \
                  -Dotel.resource.attributes=service.name=test-service \
                  -Dotel.metrics.exporter=none \
                  -Dotel.javaagent.extensions=/agents/javaagent.extension-1.0.0-SNAPSHOT.jar \
                  -Dquarkus.http.host=0.0.0.0 -Djava.util.logging.manager=org.jboss.logmanager.LogManager"

When running the application through my docker compose I get an error from opentelemetry.

Is there a way to define a receiver with the setup I have?

[Cavvar]

I think I answered the question myself.

Instead of using a OtlpGrpcSpanExporter I am using a JaegerGrpcSpanExporter now. For that I had to set the endpoint or channel. This caused the Jaeger Backend to display duplicate spans. I fixed that by simple setting the env-variable -Dotel.traces.exporter=none.

If anyone needs any clarification, feel free to ask!

[jkwatson]

Glad you got a solution. What are you trying to do here, btw? Export in-flight spans?

[Cavvar]

Not sure what in-flight spans are exactly. I am trying to explain my problem as clearly as possible.

I want to set attributes of a span during its start and after it has ended. As you know, spans during onEnd() are immutable. So the workaround I researched was to transform spans during onEnd into a readable format and then send them to an SpanExporter.

Ideally, if the exporter has been set to use jaeger (Dotel.traces.exporter=jaeger) I would want to be able to obtain that exporter through the SdkTracerProviderConfigurer or atleast inside the overriden configure() method. If that would be possible, then I could give my custom SpanProcessor that exporter and would avoid duplicate spans. The workaround right now for that would be to define none as mentioned in another discussion.

As I mentioned in my initial post, ideally a hook like beforeEnd() exists as discussed in Issue#1089. I'll might add to that issue that interests in that hook still exists.

I'm sorry if anything wasn't clear enough.

[Cavvar]

Based on the defined exporter I would want to decide which in the end I want to use. I have figured it out now by myself again I think.
I have set both metrics.exporter and traces.exporter to none and added my own JAVA_OPTIONS. Based on my custom properties I added a simple if check. Hope this clarified my intentions.

[jkwatson]

I think I finally (sorry) grok that you're asking for auto-configuration/SPI support for specifying an exporter via auto-configuration, and having it injected into your SdkTracerProviderConfigurer implementation.

I think this would start to introduce a tremendous amount of complexity in the SPI interfaces. In this case, I think you're probably best off just fully implementing what you need in your own implementation.

@anuraaga any thoughts?