Examples of Opentelemetry-cpp to support the Context Propagation via HTTP header

[r03942139]

My goal is to implement a mechanism like money tracing [1] in the opentelemetry with Jaeger, they bypass trace context in the HTTP to realize distributed tracing.
And I found that the Opentelemetry core concepts [2] support such features, and there are some related implementations [3] related.
However, I found there are no examples about how to implement it.
Is it possible that I could have more information about this used cases?
Thanks.

References:
[1] Money Tracing: The process of origin will propagate that Trace Context across system boundaries by passing the Trace Context in an HTTP Header
https://github.com/Comcast/money/wiki#how-do-we-make-distributed-tracing-work
[2] OpenTelemetry Core Concepts: Context Propagation - Propagation via HTTP headers
https://opentelemetry.lightstep.com/core-concepts/context-propagation/
[3] Some implementations related to Context Propagation in Opentelemetry-cpp
#719

[lalitb]

@r03942139 - you can find an example for HTTP context propagation here: https://github.com/open-telemetry/opentelemetry-cpp/tree/main/examples/http

[r03942139]

@lalitb
Can this example be expanded to support two exporters: OStreamSpanExporter, JaegerExporter at the same time.
The problem I hit is only the traces with error can be deployed, so I hope to debug through OStream.
Thanks.

The following is what I add to the example
https://github.com/open-telemetry/opentelemetry-cpp/blob/main/examples/http/tracer_common.h
----------------------- Start -----------------------
#include "opentelemetry/trace/propagation/jaeger.h"
namespace trace = opentelemetry::trace;
namespace jaeger = opentelemetry::exporter::jaeger;
opentelemetry::exporter::jaeger::JaegerExporterOptions opts;

auto exporter = std::unique_ptrsdktrace::SpanExporter(new jaeger::JaegerExporter(opts)); // Change from OStream to Jaeger

// Change from TextMapPropagator to JaegerPropagator
opentelemetry::context::propagation::GlobalTextMapPropagator::SetGlobalPropagator(
nostd::shared_ptropentelemetry::context::propagation::TextMapPropagator(
new opentelemetry::trace::propagation::JaegerPropagator()));
----------------------- End -----------------------

The other parts remained the same.

[lalitb]

@r03942139 - you can create two processors, each one of them connected with a separate exporter. And add these two processors to a single TracerProvider. Please refer to the example below how it is done:

https://github.com/open-telemetry/opentelemetry-cpp/blob/v1.0.0-rc3/examples/multi_processor/main.cc

[r03942139]

@lalitb
Thanks for the guidance, I used the following flow to implement context propagation with multi-processor.
The issue is that the traces will only be deployed to Jaeger, when the request is failed. (I assign to a wrong port)
When the request is successful (right port), the Jager cannot receive traces.

My question is: Do I need to add the JaegerPropagator as our global propagator either?
Thanks.

------- My flow of implementations -------
auto exporter1 = std::unique_ptrsdktrace::SpanExporter(
new opentelemetry::exporter::trace::OStreamSpanExporter);
auto processor1 = std::unique_ptrsdktrace::SpanProcessor(
new sdktrace::SimpleSpanProcessor(std::move(exporter1)));

auto exporter2 = std::unique_ptrsdktrace::SpanExporter(
new jaeger::JaegerExporter(opts));
auto processor2 = std::unique_ptrsdktrace::SpanProcessor(
new sdktrace::SimpleSpanProcessor(std::move(exporter2)));

std::vector<std::unique_ptrsdktrace::SpanProcessor> processors;
processors.push_back(std::move(processor1));
processors.push_back(std::move(processor2));

// Default is an always-on sampler.
auto context = std::make_sharedsdktrace::TracerContext(std::move(processors));
auto provider = nostd::shared_ptropentelemetry::trace::TracerProvider(new sdktrace::TracerProvider(context));

// Set the global trace provider
opentelemetry::trace::Provider::SetTracerProvider(provider);

// set global propagator
opentelemetry::context::propagation::GlobalTextMapPropagator::SetGlobalPropagator(
nostd::shared_ptropentelemetry::context::propagation::TextMapPropagator(
new opentelemetry::trace::propagation::HttpTraceContext()));
// opentelemetry::context::propagation::GlobalTextMapPropagator::SetGlobalPropagator(
// nostd::shared_ptropentelemetry::context::propagation::TextMapPropagator(
// new opentelemetry::trace::propagation::JaegerPropagator()));

---

However, the Jaeger UI only receive traces when

------ Error will send traces ------
bash-5.0$ ./opentelemetry-cpp-1.0.0-rc3/build/examples/http/http_client 1010
{
name : /helloworld
trace_id : fdfa9f0395d8c4ee18e9808998d435a0
span_id : 17f2211fe7b5fe82
.........
status : Error

}
Sueccess request will not send traces to Jaeger
bash-5.0$ ./opentelemetry-cpp-1.0.0-rc3/build/examples/http/http_client
{
name : /helloworld
trace_id : d7165329e6955168d8679f00f23d036b
span_id : 3610b691563a6524
tracestate :
parent_span_id: 0000000000000000
start : 1628110285581511155
duration : 1445337
description :
span kind : Client
status : Unset
attributes :
http.header.Date: Wed, 04 Aug 2021 20:51:25 GMT
http.header.Content-Type: text/plain
http.header.Content-Length: 0
http.header.Host: localhost
http.scheme: http
http.url: http://localhost:8800/helloworld
http.method: GET
http.header.Connection: keep-alive
http.status_code: 200
events :
links :
}

[lalitb]

@r03942139 - Sorry, the issue is not very clear to me. If you are still facing the problem, can you please elaborate it a bit.