Author

Dan Lapid <dan.lapid@gmail.com> 2026-04-19 15:56:19 +0000

Parents

062aef3

Tree

738282e

Replace startSpan with auto-ending enterSpan in user tracing

Replaces `tracing.startSpan(name) -> JsSpan` with
`tracing.enterSpan(name, callback, ...args)`, which pushes the new span
onto the AsyncContextFrame for the callback's duration and auto-ends it
on return, throw, or promise settlement. This makes nested spans and
runtime-generated spans (e.g. `fetch`) correctly parent on the
surrounding user span.

Child spans are wrapped in a fresh UserTraceSpanHolder before being
pushed onto the AsyncContextFrame; the holder is cleared by
SpanImpl::end() so actor IoContexts don't leak tracer refs across
requests.

`Span` and `SpanImpl` live in a new `workerd::api::user_tracing`
sub-namespace to avoid collision with `workerd::Span`. The JS class
name is still `Span` via `JSG_NESTED_TYPE_NAMED`.

`withSpan` in tracing-helpers.ts becomes a one-line passthrough over
`enterSpan`, so downstream callers (d1, images, etc.) need no changes.

Adds tracing-hierarchy-test which verifies parent/child relationships
in the streaming-tail event stream for nested enterSpan (sync and
async), fetch-inside-enterSpan, fetch-inside-nested-enterSpan, and
sibling enterSpan calls.