twitter/finagle

implement "b3 single" header format

Open

#719 opened on Aug 29, 2018

View on GitHub
 (4 comments) (0 reactions) (0 assignees)Scala (8,864 stars) (1,435 forks)batch import
good first issuehelp wanted

Description

Let's support at least reading "b3" header from a single string, most commonly traceid-spanid-1 It would also be nice to support optionally writing this, especially in message providers or others with constrained environments.

Expected behavior

As discussed on openzipkin/b3-propagation#21 and first implemented here: https://github.com/openzipkin/brave/blob/master/brave/src/main/java/brave/propagation/B3SingleFormat.java https://github.com/openzipkin/brave/blob/master/brave/src/test/java/brave/propagation/B3SingleFormatTest.java we should be able to parse "b3" and ideally also write it depending on config.

Actual behavior

right now, we write the historical "X-B3-" headers, which we should still support. However, if we see a header named "b3" we should read that instead.

Steps to reproduce the behavior

Turn on tracing and see if b3=80f198ee56343ba864fe8b2a57d3eff7-05e3ac9a4f6e3b90-1-e457b5a2e4d86bd1 results in the same context as:

X-B3-TraceId: 80f198ee56343ba864fe8b2a57d3eff7
X-B3-ParentSpanId: 05e3ac9a4f6e3b90
X-B3-SpanId: e457b5a2e4d86bd1
X-B3-Sampled: 1

Contributor guide

Tech stack
scala
Domain
backendobservability
Issue type
feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
half day
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
ScalaDistributed tracingB3 propagation
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
40
Research direction
Study the B3 single format specification and the existing implementation in Brave (Java). Explore how Finagle currently handles propagation headers (likely in Finagle's tracing module). Implement parsing of the 'b3' header and optionally writing it. Test with the provided example.