Any easy way to attach additional span processor?

[patsonluk]

We want to experiment with some extra functionality(profiling) that it's critical to trigger:

1. on the same thread as the instrumentation
2. immediately (synchronously) when a span is created and ended

It appears that having our own implementation of SpanProcessor would be the most ideal candidate, however, with the existing design, the easiest approach for configuration will be something similar to https://github.com/open-telemetry/opentelemetry-java/blob/main/QUICKSTART.md#tracing-sdk-configuration.

While it's not too terrible, it would have been much nicer if it can be built with some configuration option via auto config. It does seem to be a bit tricky to configure any additional span processor for auto config as the parameters right now are pretty simple (which is good), having an extra span processor config option could be messy (what exporter/sampler to attach to that)

I am wondering if there are any thoughts or suggestions for our usage? Are there something else other than SpanProcessor that we can look at?

[jkwatson]

Hi @patsonluk . This is possible today, by using the autoconfigure SPI interface: SdkTracerProviderConfigurer. By implementing this interface, you can add your own SpanProcessor at that time. If you combine this with setting your exporter option to none, then you'll have complete control over how your TracerProvider is built. If you simply want an additional SpanProcessor, then you can just have your SdkTracerProviderConfigurer implementation add a SpanProcessor and let the rest of the autoconfigure system do its thing.

Will that work for now?

[patsonluk]

Ah I have totally missed it! Thank you so much @jkwatson ! It works perfectly ;)

[patsonluk]

Oh and a quick question, is there any way to access the ConfigProperties config in TracerProviderConfiguration.configureTracerProvider(Resource resource, ConfigProperties config) from the SdkTracerProviderConfigurer ? I could see that configurer.configure(tracerProviderBuilder); is invoked on the SdkTracerProviderConfigurer but seems like the config is not available?

We want to do some initialization to our version of SdkTracerProviderConfigurer base on the config. Not a huge deal right now as we can simply call System.getProperties. Or perhaps I overlooked and it's actually available? 😅

[jkwatson]

Yes, I have been wanting to update the SPI to have the config passed in, but just haven't gotten around to it. PRs welcome! ;)