Is Remote sampling works without Jaeger-agent sampling port 5778?

[Narenderbhcu]

What happened?

Hi, We would like to know how remote sampling works without jaeger-agent sampling report?
we have configured remote sampling using OTEL GO SDK as below(intstead of jaeger-agent port 5778 we have used opentelemetry collector ports 4317 and 4318 but which is not working.

as per below link, both Jaeger Agent and OpenTelemetry Collector implement the Jaeger sampling service endpoint.

[https://github.com/open-telemetry/opentelemetry-go-contrib/tree/main/samplers/jaegerremote]

jaegerRemoteSampler := jaegerremote.New(
"your-service-name",
jaegerremote.WithSamplingServerURL("http://{sampling_service_host_name}:5778"),
jaegerremote.WithSamplingRefreshInterval(10*time.Second),
jaegerremote.WithInitialSampler(trace.TraceIDRatioBased(0.5)),
)

tp := trace.NewTracerProvider(
trace.WithSampler(jaegerRemoteSampler),
...
)
otel.SetTracerProvider(tp)

I am trying to use opentelemetry collector sampling port instead of jaeger agent port "http://{sampling_service_host_name}:5778", but I am unable to fetch sampling strategy information from the backend.
Tried with
jaegerremote.WithSamplingServerURL("http://{sampling_service_host_name}:4317"), and jaegerremote.WithSamplingServerURL("http://{sampling_service_host_name}:4318"),

but not working, please suggest your opinion.

Steps to reproduce

Try to generate traces using otel sdk by applying remote sampling as below and you can see that remote sampling not working as expected.
https://github.com/open-telemetry/opentelemetry-go-contrib/tree/main/samplers/jaegerremote
jaegerRemoteSampler := jaegerremote.New(
"your-service-name",
jaegerremote.WithSamplingServerURL("http://{sampling_service_host_name}:4317"),
or
jaegerremote.WithSamplingServerURL("http://{sampling_service_host_name}:4318"),
jaegerremote.WithSamplingRefreshInterval(10*time.Second),
jaegerremote.WithInitialSampler(trace.TraceIDRatioBased(0.5)),
)

Expected behavior

Jaeger should support remote sampling without Jaeger-agent sampling port 5778.

Relevant log output

No response

Screenshot

No response

Additional context

No response

Jaeger backend version

v1.38.0

SDK

Opentelemetry Go SDK

Pipeline

OTEL SDK -> OTEL Collector -> Jaeger Collector -> Elasticsearch -> Jaeger UI

Stogage backend

Elasticsearch

Operating system

Linux

Deployment model

kubenetes

Deployment configs

No response

[yurishkuro]

I am not sure about OTEL collector, are you sure it implements the sampling strategy endpoint on the same port as the port used to accept trace data?

With Jaeger, you do not need the agent to serve sampling strategies, Jaeger collector exposes an HTTP endpoint /api/sampling on port 14268.

https://www.jaegertracing.io/docs/1.41/deployment/#collector

[Narenderbhcu]

Hi @yurishkuro ,

Thanks for the answer. we have a question, whether client side(OTEL SDK) code need to be changed or Jaeger side code needs to be changed, in order to fix this issue? And also you mentioned that related issue on OTEL Collector, can you please share that?

[yurishkuro]

I will try to do a deep dive this weekend to get a better picture of the state. If OTEL already converged on this (deprecated) format across both OTEL collector and OTEL SDKs then it would make sense to support this format in Jaeger as a new version.

[Narenderbhcu]

Okay, we will wait, thank you so much for the support!

[yurishkuro]

I booked a ticket in OTEL: open-telemetry/opentelemetry-specification#3126

[Narenderbhcu]

Thanks @yurishkuro, we will monitor.