Missing continueFromHeaders method

[marandaneto]

When one wanna continue a trace from a header, right now it requires a bit of boilerplate and also no official docs on how to do it.

The guideline says we should provide a method called continueFromHeaders to make it easier https://develop.sentry.dev/sdk/performance/

eg Python https://github.com/getsentry/sentry-python/blob/2df9e1a230f1294b4fc319cb65838dcd6bb2e75c/sentry_sdk/tracing.py#L272

related to getsentry/sentry-docs#2984

[marandaneto]

@Tyrrrz this is relevant for you too

[maciejwalkowiak]

Currently we support:

Sentry.startTransaction(TransactionContext.fromSentryTrace("name", "op", new SentryTraceHeader("header")));

continueFromHeaders(Map<String, List<String>> headers) does not bring value for Java as HttpServletRequest does not return headers as a map. Creating a method continueFromHeaders(HttpServletRequest request) would add a dependency on javax.servlet-api to the sentry-core which we also prefer to avoid. IMO having fromSentryTrace is good enough and perhaps adding docs would be sufficient. wdyt @marandaneto ?

[Tyrrrz]

Same story on .NET:
HTTP frameworks have their own container for headers, so supporting that would require an explicit dependency on the framework.

[marandaneto]

yeah if integrations have its own wrapper around headers etc, does not make much sense, so we need to tackle this via docs, I know the API pretty well and I could not find out that I had to use the startTransaction along with fromSentryTrace in 2 minutes search, so maybe we could consider even adding a method called continueFromHeaders that takes the header and we do it internally all the boiler plate which would be:

ISpan continueFromHeader(String name, String op, String header) {
  return Sentry.startTransaction(TransactionContext.fromSentryTrace(name, op, new SentryTraceHeader(header)));
}

at least the naming is a bit more suitable to the action, so I'd not even need to read the docs.
wdyt? @bruno-garcia

[Tyrrrz]

@marandaneto would that be hub.continueFromHeader(...)? maybe a bit ambiguous as to what it's continuing?

[bruno-garcia]

To be honest I think just documenting: Sentry.startTransaction(TransactionContext.fromSentryTrace("name", "op", new SentryTraceHeader("header"))); is good enough no?

Only could be simplified to: Sentry.startTransaction(TransactionContext.fromSentryTrace("name", "op", "header")); though?

This API is only used when continuing a trace from some other system like a messaging middleware or an HTTP server so it's mostly used by integrations

[marandaneto]

IMO the problem is, people are used to using the Static sentry class, that's the entry point API for everything, they don't know about TransactionContext most probably, also SentryTraceHeader so it's a bit buried and requires some investigation to find out (if you don't have docs), most people code using auto-complete and not docs, including me, I'm fine either way, but if I could not figure out by myself within 2 minutes, it's already a red flag, as its been for users already (otherwise this issue didn't exist), we definitely can start with docs and see how it goes, but as the spec says, continueFromHeader is a thin wrapper around fromSentryTrace and startTransaction, so why not?

[adinauer]

We decided to document how to do this here https://docs.sentry.io/platforms/java/guides/spring/performance/instrumentation/custom-instrumentation/#distributed-tracing instead of adding the method.