Distributed Tracing with Jaeger

# pip install opentelemetry-distro opentelemetry-exporter-otlp
# pip install opentelemetry-instrumentation-fastapi

from fastapi import FastAPI
from opentelemetry import trace
from opentelemetry.sdk.trace import TracerProvider
from opentelemetry.sdk.trace.export import BatchSpanProcessor
from opentelemetry.exporter.otlp.proto.grpc.trace_exporter import OTLPSpanExporter
from opentelemetry.instrumentation.fastapi import FastAPIInstrumentor

# Configure tracer
provider = TracerProvider()
exporter = OTLPSpanExporter(endpoint='http://jaeger:4317')  # Jaeger OTLP endpoint
provider.add_span_processor(BatchSpanProcessor(exporter))
trace.set_tracer_provider(provider)

app = FastAPI()
FastAPIInstrumentor.instrument_app(app)  # auto-instruments all routes

tracer = trace.get_tracer(__name__)

@app.get('/orders/{order_id}')
async def get_order(order_id: int):
    with tracer.start_as_current_span('fetch-order') as span:
        span.set_attribute('order.id', order_id)

        # Manual span for a specific operation
        with tracer.start_as_current_span('db-query'):
            order = await db.get_order(order_id)

        with tracer.start_as_current_span('enrich-order'):
            user = await user_service.get_user(order.user_id)  # cross-service call

        return {'order': order, 'user': user}

# Run Jaeger all-in-one (development setup)
docker run -d \
  --name jaeger \
  -p 16686:16686 \
  -p 4317:4317 \
  -p 4318:4318 \
  jaegertracing/all-in-one:latest

# Ports:
# 16686 — Jaeger UI
# 4317  — OTLP gRPC receiver
# 4318  — OTLP HTTP receiver

# Open Jaeger UI: http://localhost:16686
# Search by service name → see all traces
# Click a trace → see full span timeline
# Click a span → see attributes, events, errors