Asymmetry in extractor vs injector breaks propagation

[meltsufin]

The extractor always prioritizes GCP headers (X-Cloud-Trace-Context) over the Brave headers.
However, the injector only propagates traces in the Brave headers. The GCP load-balancer will generate X-Cloud-Trace-Context header when one is not present. This causes a break in the trace propagation from service A to B.

I see two possible solutions:

1. Injector should inject both X-Cloud-Trace-Context and X-B3-* headers.
2. Extractor should prioratize X-B3-* headers over X-Cloud-Trace-Context.

See: spring-attic/spring-cloud-gcp#1019

cc/ @saturnism

[codefromthecrypt]

ps "Brave headers" is a little imprecise probably a hundred libraries use B3 :P

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On Fri, Sep 14, 2018 at 11:02 PM Mike Eltsufin ***@***.***> wrote: The extractor always prioritizes GCP headers (X-Cloud-Trace-Context) over the Brave headers. However, the injector only propagates traces in the Brave headers. The GCP load-balancer will generate X-Cloud-Trace-Context header when one is not present. This causes a break in the trace propagation from service A to B. I see two possible solutions: 1. Injector should inject both X-Cloud-Trace-Context and X-B3-* headers. 2. Extractor should prioratize X-B3-* headers over X-Cloud-Trace-Context. See: spring-attic/spring-cloud-gcp#1019 <spring-attic/spring-cloud-gcp#1019> cc/ @saturnism <https://github.com/saturnism> — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#96>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AAD611yMebDJKJT0jKuBwu5C3vXGuNgQks5ua8UPgaJpZM4WpcCh> .

[codefromthecrypt]

I would recommend a couple things: 1. file a ticket with GCP load balancer to understand B3 headers. Since many including census libraries also can send these as many others sooner is better than later 2. I think your option of prioritizing B3 first will result in less trace breaking because you can't control all the other libraries in the ecosystem. * If you can, then you could prioritize as currently then dual-propagate X-Cloud-Trace-Context

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On Fri, Sep 14, 2018 at 11:02 PM Mike Eltsufin ***@***.***> wrote: The extractor always prioritizes GCP headers (X-Cloud-Trace-Context) over the Brave headers. However, the injector only propagates traces in the Brave headers. The GCP load-balancer will generate X-Cloud-Trace-Context header when one is not present. This causes a break in the trace propagation from service A to B. I see two possible solutions: Injector should inject both X-Cloud-Trace-Context and X-B3-* headers. Extractor should prioratize X-B3-* headers over X-Cloud-Trace-Context. See: spring-attic/spring-cloud-gcp#1019 cc/ @saturnism — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub, or mute the thread.

[meltsufin]

You are basically suggesting combining both proposed solutions. Makes sense.

[codefromthecrypt]

I meant do both 1 and 2.

I maybe mis-phrased the bullet:

• If you can, then you could prioritize as currently then
  dual-propagate X-Cloud-Trace-Context

The sub-point to two was meant to be phrased unlikely. For example, it isn't likely to be in a homogenous X-Cloud-Trace-Context, hence this issue. It is even less likely going forward with tracecontext etc. So, prioritizing X-Cloud-Trace-Context (over b3) probably isn't much sense, and the incidental work dual-propagating X-Cloud-Trace-Context is also less sensible AFAICT.