servant-tracing

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Versions [RSS] 0.1.0.0, 0.1.0.1, 0.1.0.2, 0.2.0.0
Change log ChangeLog.md
Dependencies aeson (>=2.0.1.0 && <3), async, base (>=4.7 && <5), bytestring, bytestring-lexing, containers, hashable, http-api-data, http-client, http-types, lifted-base, monad-control, mtl, random, servant, text, time, unordered-containers, wai [details]
License MIT
Copyright 2018-2021 Chris Coffey
Author Chris Coffey
Maintainer chris@coffey.dev
Home page https://github.com/ChrisCoffey/haskell-opentracing-light#readme
Bug tracker https://github.com/ChrisCoffey/haskell-opentracing-light/issues
Source repo head: git clone https://github.com/ChrisCoffey/haskell-opentracing-light
Uploaded by ChrisCoffey at 2021-12-19T20:54:18Z
Distributions NixOS:0.2.0.0
Downloads 1597 total (14 in the last 30 days)
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Status Docs available [build log]
Last success reported on 2021-12-19 [all 1 reports]

Readme for servant-tracing-0.2.0.0

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servant-tracing

Build Status

This repository is the minimum required for publishing trace data to Zipkin or Jaeger. It adheres to the Open Tracing Standard but is missing a few features. See the documentation on Hackage for module-level details.

Using the library

The OpenTracing standard revolves around a single function, recordSpan. recordSpan is responsible for creating new spans (see the standard for the definition of a span) and ensuring child spans use the new id. In order to properly build this tree of calls library users must provide the necessary environment via a MonadTracer instance (see haddocks). Library users are responsible for defining their own publish loop. There is a default Zipkin publisher in Tracing.Zipkin which works with Jaeger & Zipkin, but the loop to drain the spanBuffer must be provided by the user.

foo :: (MonadIO m, MonadTracer m) =>
    Int
    -> m String
foo str = recordSpan
    Nothing
    [Tag "Ultimate Answer to Life, The Universe and Everything", Tag 42]
    "Compute Ultimate Question"
    $ pure "Oops"

The code above logs a new span to the spanBuffer, where it will sit until published. If it turns out that foo is called from an active span, then it will be recorded as a child of said higher span.

Testing Locally with the Demo App

You can start up a compatible server for Zipkin or Jaeger via a standalone docker container. From there its a matter of seting the following environment variables:

  • TRACING_ENDPOINT: a String with the fully url to a running tracing server. For example, http://localhost:9411/api/v2/spans to publish to a Zipkin endpoint.
  • TRACING_SERVICE: a String name for your service

Once the a tracing server & the example service are running, you can interact with it via your favorite REST client. The api expects a header named Auth, and has two top level endpoints: fast & slow. Here's an example request: curl localhost:8080/slow -HAUTH="foo"

Pending Features

  • Thrift support
  • Additional clients
  • Pluggable samplers