W3C Trace Context support

[stephanie-anderson]

getsentry/team-sdks#41

[jamescrowley]

@stephanie-anderson @AbhiPrasad would you be open to a PR for this, along the lines of the PHP library support (getsentry/sentry-php#1680, getsentry/sentry-php#1713) using getsentry/team-sdks#41 (comment) to generate the traceparent value? I'd be happy to put something together

[Lms24]

Hi @jamescrowley thanks for offering to open a PR! At the moment we're still figuring out a somewhat related issue with trace propagation (more specifically, how to avoid propagating traces across multiple sentry orgs/customers). So we didn't move forward with implementing this. In JS (browser) specifically, we also can't hard-switch to traceparent because it would break all users who have to allow-list Http headers in their CORS configuration. Once we have things figured out, we'll ping you if we deem it okay to be implemented by the community. Thanks again!

[cleptric]

@jamescrowley could you shed some light on your supposed use-case for the traceparent header?

[jamescrowley]

@cleptric we have an React SPA with no server-side rendering. We're looking to align the trace identifiers that Sentry generates on the client, with the server logs on the Google Cloud side.

At the moment, server-side requests receive a conflicting traceparent from the Google infrastructure and a sentry-trace from the client-side request that has been intercepted by Sentry, but that's not something we can get the GCP side to use.

Hope that makes sense, happy to explore further - or indeed if there are alternatives to achieving this. I had a look at hooking into the fetch interception logic on the Sentry client when you create the span ids and inject the sentry-trace header (addTracingHeadersToFetchRequest), but there doesn't appear to be a 'nice' point to do that.

Given ^^ I'll look now at creating our own span when making web requests, and adding our own header using the logic outlined here getsentry/team-sdks#41 (comment) - which (not verified yet) but hopefully Sentry will then re-use the existing span for the request so the two match.

[cleptric]

Our main goal, if we add support for the traceparent header, would be to support use-cases where all applications in the "trace chain" would report their telemetry to Sentry. An application receiving a 3rd party tracing header and thus sampling a trace results into a quota issue, as you typically do not want to continue a trace from an unknown 3rd party.
Fwiw, we actually ran into a couple of issues with the implementation in PHP, hence we held off adding this to other SDKs for the time being.