Tracing.continue_from! with a block maintains active trace until the block ends #4941

marcotc · 2025-10-04T01:14:20Z

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 · 2025-10-04T01:14:30Z

Thank you for updating Change log entry section 👏

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

…block ends

pr-commenter · 2025-10-04T01:40:55Z

Benchmarks

Benchmark execution time: 2025-12-08 17:55:39

Comparing candidate commit 0524bd4 in PR branch fix-trace-auto-finish with baseline commit 48b4d79 in branch master.

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

scenario:profiling - stack collector (ruby frames - native filenames enabled)

🟩 throughput [+207.147op/s; +209.317op/s] or [+6.636%; +6.705%]

datadog-official · 2025-10-04T01:43:42Z

✅ Tests

🎉 All green!

❄️ No new flaky tests detected
🧪 All tests passed

🎯 Code Coverage
• Patch Coverage: 100.00%
• Total Coverage: 95.23% (-0.00%)

View detailed report

_{This comment will be updated automatically if new data arrives.

🔗 Commit SHA: 0524bd4 | Docs | Datadog PR Page | 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.

lib/datadog/tracing/trace_operation.rb

lib/datadog/tracing/tracer.rb

Strech

LGTM 👍🏼

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

Strech · 2025-10-07T08:06:22Z

lib/datadog/tracing/tracer.rb

+        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


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

I actually prefer the current version in the PR because the proposed revision adds several negations.

Strech · 2025-10-07T08:08:05Z

spec/datadog/tracing/tracer_spec.rb

+              # Don't finish the span, so finished_span_count remains 0
+            end
+
+            # No spans should be flushed


I think comment is unnecessary

Suggested change

# No spans should be flushed

I guess it's there for emphasis?

ivoanjo · 2025-11-27T09:06:31Z

Hey, should we go ahead and merge this one?

* master: (523 commits) DI: relax upper bound for reported long method duration (#5113) Change development guide to use Ruby 3.4 by default (#5112) Fix exception in RC on OpenFeature::Engine absence [🤖] Update Latest Dependency: https://github.com/DataDog/dd-trace-rb/actions/runs/19996135509 [🤖] Update System Tests: https://github.com/DataDog/dd-trace-rb/actions/runs/19996155319 Add ruby guikld to all dsm files add DSM to codeowners feat: add process tags to traces (#5033) DEBUG-3558 DI: chunk snapshot payloads (#5086) CI: enable push_to_test_optimization unless this is a pull request from a fork fix steep checks [🤖] Lock Dependency: https://github.com/DataDog/dd-trace-rb/actions/runs/19827679824 [🤖] Lock Dependency: https://github.com/DataDog/dd-trace-rb/actions/runs/19827296218 Add test to verify consumer backlog serialization with kafka_commit tag Remove one diagnostic output Install rubygems Add diagnostic steps Use default rubygems+bundler for each Ruby version Revert "Disable profiling specs for 4.0" Use git `datadog-ruby_core_source` having 4.0 ...

p-datadog · 2025-12-10T22:46:27Z

I will be clicking the merge button on this after the release is complete.

marcotc requested review from a team as code owners October 4, 2025 01:14

marcotc requested a review from vpellan October 4, 2025 01:14

github-actions bot added the tracing label Oct 4, 2025

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

eb4376a

…block ends

marcotc force-pushed the fix-trace-auto-finish branch from 91fa0bb to eb4376a Compare October 4, 2025 01:26

maycmlee reviewed Oct 6, 2025

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p-datadog approved these changes Oct 6, 2025

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lib/datadog/tracing/trace_operation.rb Outdated Show resolved Hide resolved

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Strech approved these changes Oct 7, 2025

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vpellan approved these changes Oct 13, 2025

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Update lib/datadog/tracing/trace_operation.rb

07fbccb

p-datadog requested a review from a team as a code owner December 8, 2025 17:19

p and others added 4 commits December 8, 2025 12:22

standard

1633bc8

remove rubocop declarations

0970a2b

Merge branch 'master' into fix-trace-auto-finish

0524bd4

Tracing.continue_from! with a block maintains active trace until the block ends #4941

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Tracing.continue_from! with a block maintains active trace until the block ends #4941

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