AioZipkin middleware for Starlette/FastApi

Features

• Using sentry-asgi as a boilerplate
• Client - based on aiozipkin - async compatible zipkin library
• Server (any zipkin 2.0 compatible server will work) - Jaeger examples
• Middleware tracing http traffic
• Injecting tracing headers to responses
• Extracting tracing headers from requests
• Context variable with the span for every incoming request - possible to instrument tracing of lower level operations

Quick start

Run tracing server

Jaeger all-in-one

Follow instructions at https://www.jaegertracing.io/docs/latest/getting-started/

$ docker run -d --name jaeger \
  -e COLLECTOR_ZIPKIN_HTTP_PORT=9411 \
  -p 5775:5775/udp \
  -p 6831:6831/udp \
  -p 6832:6832/udp \
  -p 5778:5778 \
  -p 16686:16686 \
  -p 14268:14268 \
  -p 9411:9411 \
  jaegertracing/all-in-one:latest

Trace queries at http://localhost:16686/

Add middleware

import uvicorn
from starlette.applications import Starlette
from starlette.responses import JSONResponse
from starlette.routing import Route

from starlette_zipkin import ZipkinMiddleware

routes = [
    Route("/", JSONResponse({"status": "OK"})),
]

app = Starlette(debug=True, routes=routes)

app.add_middleware(ZipkinMiddleware)

if __name__ == "__main__":
    uvicorn.run(app, host="0.0.0.0", port=8000, log_level="info", reload=True)

By default the client emits to http://localhost:9411.

All traffic is captured and available at http://localhost:16686/

Advanced Tutorial

To instrument tracing at lower levels, two helper functions are available:

• get_root_span - returns the span instance corresponding to current request
• get_tracer - returns the tracer instance corresponding to current request
• trace - create span in the trace

import json
import asyncio
import uvicorn
from starlette.applications import Starlette
from starlette.responses import JSONResponse
from starlette.routing import Route

from starlette_zipkin import (
    ZipkinMiddleware,
    ZipkinConfig,
    trace,
    B3Headers,
    UberHeaders
)

async def homepage(request):

    with trace("NewParent") as child_span:
        # ! if headers not explicitly provided,\
        # root span from middleware injects headers
        # and becomes the parent for subsequet services
        headers = child_span.context.make_headers()
        child_span.kind("SERVER")
        # possible span kinds
        # CLIENT = "CLIENT"
        # SERVER = "SERVER"
        # PRODUCER = "PRODUCER"
        # CONSUMER = "CONSUMER"
        child_span.annotate(
            "Child, sleeps for 1, injects headers and becomes parent"
        )
        await asyncio.sleep(1)
        return JSONResponse({"hello": "world"}, headers=headers)

routes = [
    Route("/", JSONResponse({"status": "OK"})),
    Route("/homepage", homepage),
]

app = Starlette(debug=True, routes=routes)

config = ZipkinConfig(
    host="localhost",
    port=9411,
    service_name="service_name",
    sample_rate=1.0,
    inject_response_headers=True,
    force_new_trace=False,
    json_encoder=json.dumps,
    header_formatter=B3Headers
)
app.add_middleware(ZipkinMiddleware, config=config)

if __name__ == "__main__":
    uvicorn.run(app, host="0.0.0.0", port=8000, log_level="info", reload=True)

This way we are able to followup at the call from a different service. Here we use the same server, but pass the tracing headers to subsequent calls to demonstrate future spans:

Configuration

To change the middleware configuration, provide a config object (here with default values being as shown)

import json
from starlette_zipkin import ZipkinMiddleware, ZipkinConfig, B3Headers

config = ZipkinConfig(
    host="localhost",
    port=9411,
    service_name="service_name",
    sample_rate=1.0,
    inject_response_headers=True,
    force_new_trace=False,
    json_encoder=json.dumps,
    header_formatter=B3Headers
)

app = Starlette()

app.add_middleware(ZipkinMiddleware, config=config)

where:

• host = "localhost"
  • default local host, needs to be set to point at the agent that collects traces (e.g. jaeger-agent)
• port = 9411
  • default port, needs to be set to point at the agent that collects traces (e.g. jaeger-agent)
  • 9411 is default for zipkin client/agent (and jaeger-agent)
  • make sure to make accessible
• service_name = "service_name"
  • name of the service
• sample_rate = 1.0
  • zipkin sampling rate, default samples every call
• inject_response_headers = True
  • automatically inject response headers
• force_new_trace = False
  • if True, does not create child traces if incoming request contains tracing headers
• json_encoder=json.dumps
  • json encoder can be provided, defaults to json dumps. It is used to format dictionaries for Jaeger UI.
• header_formatter=B3Headers
  • defaults to b3 headers format. Can be switched to UberHeaders, which imply the uber-trace-id format.