Document baggage propagation

[veeral-patel]

Thanks for this great project! However, I noticed propagating baggage across network calls is not documented. I needed to go through the code to find a solution.

Here is a example code snippet we could clean up and add to the cookbook:
https://opentelemetry.io/docs/concepts/signals/traces/#context-propagation

Below, api1 calls api2:

api1:

from flask import Flask
import requests
from opentelemetry import trace, propagators, baggage
from opentelemetry.instrumentation.flask import FlaskInstrumentor
from opentelemetry.instrumentation.requests import RequestsInstrumentor
from opentelemetry.trace.propagation.tracecontext import TraceContextTextMapPropagator
from opentelemetry.baggage.propagation import W3CBaggagePropagator
from opentelemetry.sdk.trace import TracerProvider
from opentelemetry.sdk.trace.export import ConsoleSpanExporter, BatchSpanProcessor
from opentelemetry.exporter.jaeger.thrift import JaegerExporter

app = Flask(__name__)

trace.set_tracer_provider(TracerProvider())
trace.get_tracer_provider().add_span_processor(BatchSpanProcessor(ConsoleSpanExporter()))

jaeger_exporter = JaegerExporter(
    agent_host_name="localhost",  # Set your Jaeger agent host
    agent_port=6831,  # Set your Jaeger agent port
)
trace.get_tracer_provider().add_span_processor(BatchSpanProcessor(jaeger_exporter))

tracer = trace.get_tracer(__name__)

@app.route('/')
def hello():
    with tracer.start_as_current_span("api1_span") as span:
        ctx = baggage.set_baggage("hello", "world")

        headers = {}
        W3CBaggagePropagator().inject(headers, ctx)
        TraceContextTextMapPropagator().inject(headers, ctx)
        print(headers)

        response = requests.get('http://127.0.0.1:5001/', headers=headers)
        return f"Hello from API 1! Response from API 2: {response.text}"

if __name__ == '__main__':
    app.run(port=5002)

api2:

from flask import Flask, request
from opentelemetry import trace, baggage
from opentelemetry.instrumentation.flask import FlaskInstrumentor
from opentelemetry.trace.propagation.tracecontext import TraceContextTextMapPropagator
from opentelemetry.sdk.trace import TracerProvider
from opentelemetry.sdk.trace.export import ConsoleSpanExporter, BatchSpanProcessor
from opentelemetry.exporter.jaeger.thrift import JaegerExporter
import time
from opentelemetry.baggage.propagation import W3CBaggagePropagator

app = Flask(__name__)

trace.set_tracer_provider(TracerProvider())
trace.get_tracer_provider().add_span_processor(BatchSpanProcessor(ConsoleSpanExporter()))

jaeger_exporter = JaegerExporter(
    agent_host_name="localhost",  # Set your Jaeger agent host
    agent_port=6831,  # Set your Jaeger agent port
)
trace.get_tracer_provider().add_span_processor(BatchSpanProcessor(jaeger_exporter))

tracer = trace.get_tracer(__name__)

@app.route('/')
def hello():
    # Example: Log headers received in the request in API 2
    headers = dict(request.headers)
    print(f"Received headers: {headers}")
    carrier ={'traceparent': headers['Traceparent']}
    ctx = TraceContextTextMapPropagator().extract(carrier=carrier)
    print(f"Received context: {ctx}")

    b2 ={'baggage': headers['Baggage']}
    ctx2 = W3CBaggagePropagator().extract(b2, context=ctx)
    print(f"Received context2: {ctx2}")

    # Start a new span
    with tracer.start_span("api2_span", context=ctx2):
       # Use propagated context
        print(baggage.get_baggage('hello', ctx2))
        return "Hello from API 2!"

if __name__ == '__main__':
    app.run(port=5001)

[ocelotl]

Hello @veeral-patel, it seems like you already have a solution for this issue. Could you open a PR here?

[pegasas]

Hello @veeral-patel, it seems like you already have a solution for this issue. Could you open a PR here?

I've open an PR for this, feel free to comments if any concern.