tryfer: A Twisted Zipkin Tracer Library

Zipkin is a Distributed Tracing system, tryfer is a Python/Twisted client library for Zipkin.

It's design is heavily influenced by Finagle's tracing libraries.

Tracing

The Zipkin system primarily deals with the collection and analyzation of requests. It does not define how tracing contexts are passed between distributed systems.

Finagle, Twitter's project, is a base structure for services. It handles all of the inter-service communication details. The inter-service communication details include how a tracing context is passed between systems.

Tryfer defines a TracingAgent and a TracingWrapperResource for Twisted services. These objects can pass along tracing contexts between services speaking HTTP and using Twisted. This library is mostly compatible with Finagle based services. It supports client side and server side connections to Finagle based services. (In addition to client side and server side connections to services using this library).

See here for Finagle's method of passing the tracing context over HTTP.

Any Zipkin client library must provide a way to log Trace s to the Zipkin Collector. The Zipkin Collector speaks Scribe's protocol. So this is usually accomplished by either pointing the Scribe client to either a Scribe instance, and having the Scribe instance point to the Zipkin collector. Or, having the Scribe client point directly at the Zipkin collector. Our tracers can be found in the module tracers.

HTTP Tracing

Tryfer natively supports tracing of HTTP requests on both the client and the server, and relates these requests by passing a series of HTTP headers along with the request.

Client

The client side of this conversation is the TracingAgent which uses Twisted's composable HTTP/1.1 client architecture to record CLIENT_SEND and CLIENT_RECV annotations for your request. In addition it'll record the full requested URL as a string annotation named http.uri.

Server

On the server you can wrap the root resource of your application in a TracingWrapperResource and it will automatically record SERVER_RECV and SERVER_SEND annotations. It also provides access to the trace via the request argument, so you can record extra annotations.

def render(self, request):
  trace = request.getComponent(ITrace)
  trace.record(Annotation.string('name', 'value'))

Headers

TracingAgent and TracingWrapperResource support a subset of headers defined by Finagle.

• X-B3-TraceId - hex encoded trace id.
• X-B3-SpanId - hex encoded span id.
• X-B3-ParentSpanId - hex encoded span id of parent span.

Examples

In the examples/ subdirectory you'll find two python scripts (one client and one server) which demonstrate the usage and expected output.

Start by opening two terminals and going to the tryfer source directory.

In terminal #1 we can start the server using twistd:

tryfer> twistd -n -y examples/tracing-server.tac
2012-09-05 13:22:02-0700 [-] Log opened.
2012-09-05 13:22:02-0700 [-] twistd 12.1.0 (/Users/dreid/.virtualenvs/tracing/bin/python 2.7.2) starting up.
2012-09-05 13:22:02-0700 [-] reactor class: twisted.internet.selectreactor.SelectReactor.
2012-09-05 13:22:02-0700 [-] Site starting on 8080
2012-09-05 13:22:02-0700 [-] Starting factory <twisted.web.server.Site instance at 0x100e78680>

In terminal #2 we will run the client which will make a single HTTP request to the server:

tryfer> python examples/tracing-client.py
[
  {
    "annotations": [
      {
        "type": "string",
        "value": "http://localhost:8080/README.rst",
        "key": "http.uri"
      },
      {
        "type": "timestamp",
        "value": 1346876525257644,
        "key": "cs"
      },
      {
        "type": "timestamp",
        "value": 1346876525270536,
        "key": "cr"
      }
    ],
    "trace_id": "00e5f721d19e25fa",
    "name": "GET",
    "span_id": "007fe79f2c63db97"
  }
]
Received 200 response.

Here we see some output from the DebugTracer which simply prints all annotations it's asked to trace to stdout in json format. Here we've included our first annotation which is the http.uri we are requesting.

Now in terminal #1 we should see the following:

2012-09-05 13:22:05-0700 [HTTPChannel,0,127.0.0.1] 127.0.0.1 - - [05/Sep/2012:20:22:05 +0000] "GET /README.rst HTTP/1.1" 200 4829 "-" "-"
2012-09-05 13:22:05-0700 [EndAnnotationTracer] Sending trace: (64729494289524218, 36001992872811415) w/ (<tryfer.trace.Annotation object at 0x100e7bb90>,)
[
  {
    "annotations": [
      {
        "host": {
          "service_name": "tracing-server-example",
          "ipv4": "127.0.0.1",
          "port": 8080
        },
        "type": "timestamp",
        "value": 1346876525268525,
        "key": "sr"
      },
      {
        "host": {
          "service_name": "tracing-server-example",
          "ipv4": "127.0.0.1",
          "port": 8080
        },
        "type": "timestamp",
        "value": 1346876525270173,
        "key": "ss"
      }
    ],
    "trace_id": "00e5f721d19e25fa",
    "name": "GET",
    "span_id": "007fe79f2c63db97"
  }
]

License

Copyright (C) 2012 Rackspace Hosting, Inc

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.