Tracing.continue_from! with a block maintains active trace until the block ends

[marcotc]

What does this PR do?

Fixes an unintended behavior of Datadog::Tracing.continue_from!(digest, &block) where if multiple local root spans are created inside a the block, only the first one is associated with the digest. Any subsequence spans inside that block are associated with a new, unrelated trace.

Effectively, this PR makes this block do what it looks like it does:

# Capture TraceDigest
digest = Datadog::Tracing.active_trace.to_digest

# Then in another thread
Datadog::Tracing.continue_trace!(digest) do
  tracer.trace('first.span') {} # Both spans are associated
  tracer.trace('second.span') {} # with the digest
end

Before this PR, only the first.span would be associated with the digest.

Motivation:

While trying to address #3465, I wasn't able to get all background spans to be associated with the active span in the main calling thread. This was due to the bug that this PR fixes.

Change log entry

Yes. Tracing.continue_from! with a block maintains active trace until the block ends.

[github-actions]

Thank you for updating Change log entry section 👏

^{Visited at: 2025-10-04 02:07:44 UTC}

[pr-commenter]

Benchmarks

Benchmark execution time: 2025-10-04 01:56:31

Comparing candidate commit eb4376a in PR branch fix-trace-auto-finish with baseline commit eae7fc6 in branch master.

Found 0 performance improvements and 1 performance regressions! Performance is the same for 43 metrics, 2 unstable metrics.

scenario:tracing - Tracing.log_correlation

• 🟥 throughput [-7981.466op/s; -7693.495op/s] or [-7.359%; -7.094%]

[datadog-official]

✅ Tests

🎉 All green!

❄️ No new flaky tests detected
🧪 All tests passed

🎯 Code Coverage
• Patch Coverage: 103.27%
• Total Coverage: 101.97% (-0.01%)

View detailed report

_{This comment will be updated automatically if new data arrives.
🔗 Commit SHA: eb4376a | Docs | Was this helpful? Give us feedback!}

[maycmlee]

Nothing for docs to review

[p-datadog]

I think this branch is missing #4925, if so it should have master merged into it and formatters rerun.

[p-datadog]

Suggested change

	@auto_finish = auto_finish
	@auto_finish = !!auto_finish

[p-datadog]

Was this rubocop autocorrected? If yes this branch needs master merged into it I think.

[Strech]

LGTM 👍🏼

P.S I've left few non-blocking suggestions

[Strech]

This could be streamlined with a guard-clause

Suggested change

	if block
	# When a block is given, the trace will be active until the block finishes.
	context.activate!(trace) do
	yield
	ensure # We have to flush even when an error occurs
	# On block completion, force the trace to finish and flush its finished spans.
	# Unfinished spans are lost as the {TraceOperation} has ended.
	trace.finish!
	flush_trace(trace)
	end
	else
	# Otherwise, the trace will be bound to the current thread after this point
	context.activate!(trace)
	end
	# The trace will be bound to the current thread if no block is given
	return context.activate!(trace) unless block
	# When a block is given, the trace will be active until the block finishes.
	context.activate!(trace) do
	yield
	ensure # We have to flush even when an error occurs
	# On block completion, force the trace to finish and flush its finished spans.
	# Unfinished spans are lost as the {TraceOperation} has ended.
	trace.finish!
	flush_trace(trace)
	end

[Strech]

I think comment is unnecessary

Suggested change

# No spans should be flushed