Pre-construct TagMap.Entry objects in InternalTagsAdder by dougqh · Pull Request #11555 · DataDog/dd-trace-java

dougqh · 2026-06-04T00:12:48Z

What Does This Do

InternalTagsAdder sets _dd.base_service / version on spans via TagMap.set(tag, value), which allocates a fresh TagMap.Entry per span. Both values are fixed for the life of the tracer, and TagMap.Entry objects are explicitly safe to share across maps (the OptimizedTagMap collision design via BucketGroup relies on it). This pre-builds the two Entry objects once in the constructor and reuses them via set(entry).

Motivation

A JFR allocation profile of spring-petclinic under load (full agent, 2026-06-03) attributed ~52 allocation samples to InternalTagsAdder.processTags — one Entry allocated per span for base.service. Tag-map handling (TagMap$Entry + OptimizedTagMap) was the single largest non-core tracer allocation theme in that profile, ahead of the CSS metrics system. This change drops the InternalTagsAdder contribution to zero.

Notes

Re-applies the logic from Reuse TagMap.Entry objects in InternalTagsAdder #10965 (dd/pre-construct-tagmap-entries), which had drifted 415 commits behind master and changed processTags's signature; this version sits on current master with the unchanged AppendableSpanLinks signature. Supersedes Reuse TagMap.Entry objects in InternalTagsAdder #10965.
Behavior preserved: Entry.stringValue() for the OBJECT entry resolves to obj.toString() (cached), identical to the prior ddService.toString() in the equalsIgnoreCase comparison. The only edge case — empty ddService now yields an early return — is unreachable in production (Config.getServiceName() is never "").
Existing test InternalTagsAdderTest.groovy passes unchanged.

🤖 Generated with Claude Code

InternalTagsAdder set base.service / version via TagMap.set(tag, value), allocating a fresh TagMap.Entry per span. Both values are fixed for the life of the tracer, and TagMap.Entry objects are safe to share across maps (the OptimizedTagMap collision design relies on it), so build the two Entry objects once in the constructor and reuse them via set(entry). A JFR profile of petclinic (2026-06-03) attributed ~52 allocation samples to InternalTagsAdder.processTags (one Entry per span); this drops them to zero. Re-applies the change from the stale PR #10965 (415 commits behind master, drifted signature) onto current master. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

dd-octo-sts · 2026-06-04T00:14:16Z

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datadog-datadog-prod-us1-2 · 2026-06-04T00:14:42Z

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chatgpt-codex-connector · 2026-06-04T00:17:50Z

-    this.version = version != null && !version.isEmpty() ? UTF8BytesString.create(version) : null;
+    this.baseServiceEntry =
+        ddService != null
+            ? TagMap.Entry.create(DDTags.BASE_SERVICE, UTF8BytesString.create(ddService))


Preserve version handling for empty DD_SERVICE

When DD_SERVICE is explicitly set to an empty string, this now becomes null because TagMap.Entry.create(String, CharSequence) returns null for empty values, while Config can still pass through an empty configured service name from the config provider. In that scenario a span whose service name is also empty used to reach the version branch and add DD_VERSION, but the new baseServiceEntry == null guard exits before versionEntry is considered, silently dropping the version tag for that configuration.

Useful? React with 👍 / 👎.

Good catch — fixed in f5f5cc9. The constructor now keeps a separate ddService UTF8BytesString handle that drives both the early-return guard and the case-insensitive service-name comparison (independent of whether baseServiceEntry was prebuilt). For the empty-DD_SERVICE case, Entry.create still returns null, so the base.service branch falls back to unsafeTags.set(BASE_SERVICE, ddService) — preserving byte-identical behavior — and crucially the version branch is still reached when the span's service name also matches the empty configured service.

I added regression coverage in the migrated InternalTagsAdderTest (now JUnit 5): new InternalTagsAdder("", "1.0") with an empty span service still adds version 1.0, and with a non-empty span service it takes the base.service branch and adds no version.

(Reply by Claude)

Addresses the Codex review comment on #11555: pre-building the base.service Entry must not change behavior for an explicitly-empty DD_SERVICE. Entry.create rejects empty values, so baseServiceEntry is null in that case; the processTags branch now falls back to set(BASE_SERVICE, ddService) to preserve byte-identical behavior, and the version branch is still reached when the span service also matches the empty configured service. Migrate InternalTagsAdderTest from Groovy/Spock to JUnit 5 (parameterized with @MethodSource) and add regression coverage for the empty-DD_SERVICE case (9 migrated cases + 2 new = 11). Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

dd-octo-sts · 2026-06-04T01:38:31Z

🟢 Java Benchmark SLOs — All performance SLOs passed

Suite	Status
Startup	🟢 pass

SLO thresholds are defined here based on automatically generated metrics. A warning is raised when results are within 5% of the threshold.

PR vs. master results

Scenario	Candidate	master	Δ (95% CI of mean)
startup:insecure-bank:iast:Agent	14.01 s	13.93 s	[-0.2%; +1.4%] (no difference)
startup:insecure-bank:tracing:Agent	12.92 s	13.03 s	[-1.7%; +0.0%] (no difference)
startup:petclinic:appsec:Agent	16.93 s	16.82 s	[-0.5%; +1.8%] (no difference)
startup:petclinic:iast:Agent	16.98 s	16.99 s	[-1.1%; +1.0%] (no difference)
startup:petclinic:profiling:Agent	16.76 s	16.92 s	[-1.8%; -0.1%] (maybe better)
startup:petclinic:sca:Agent	16.79 s	16.87 s	[-2.1%; +1.0%] (no difference)
startup:petclinic:tracing:Agent	16.14 s	16.11 s	[-1.3%; +1.6%] (no difference)

Commit: 01773bfd · CI Pipeline · Benchmarking Platform UI

Load and DaCapo benchmarks can be triggered manually in the GitLab pipeline. Results will appear in the Benchmarking Platform UI after completion.

amarziali

it looks a good idea. I left improvements for the comments specifically that looks a bit too verbosely generated

amarziali · 2026-06-08T14:11:45Z

+import org.mockito.junit.jupiter.MockitoExtension;
+
+@ExtendWith(MockitoExtension.class)
+class InternalTagsAdderTest {


Even if we have policy to migrate to junit, did you add some new test? Otherwise it can be migrated separately

Yes, I believe some tests were added to cover some corner cases.

amarziali · 2026-06-08T14:14:21Z

+  // ddService drives the guard and the service-name comparison; kept even when empty so behavior
+  // matches the prior implementation exactly (an explicitly-empty DD_SERVICE is a valid, if
+  // degenerate, config -- see getStringExcludingSource, which passes "" through, not the default).


This looks a generated comment that is not adding information about the ddService variable itself but more related to the changes on this PR specifically

amarziali · 2026-06-08T14:15:13Z

+  // base.service / version values are fixed for the life of the tracer, and TagMap.Entry objects
+  // are safe to share across maps (the OptimizedTagMap collision design relies on it), so the
+  // entries are built once and reused on the hot path instead of allocating one per span.
+  // baseServiceEntry is null when ddService is null OR empty (Entry.create rejects empty values);
+  // the empty case falls back to set(tag, value) below to preserve byte-identical behavior.


That's useful I would make it more concise (looks generated)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

@TableTest

…gression test Preserves the @TableTest versions of the two existing tests that landed on master, and adds the empty-DD_SERVICE regression test (from the PR) as a plain @test. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

- Extend the processTags null guard to also exit when ddService.length()==0, which prevents writing _dd.base_service="" via the TagMap.set path that has no empty-value guard (unlike Entry.create). Empty ddService now behaves the same as null/unset. - Remove the manual null+length>0 pre-check before TagMap.Entry.create in the constructor; Entry.create already returns null for null or empty values, so the guard was redundant. - Update the regression test to assert the new early-return behavior. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

dougqh mentioned this pull request Jun 4, 2026

Reuse TagMap.Entry objects in InternalTagsAdder #10965

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dougqh marked this pull request as ready for review June 4, 2026 00:14

dougqh requested a review from a team as a code owner June 4, 2026 00:14

dougqh requested a review from ygree June 4, 2026 00:14

dd-octo-sts Bot added the tag: ai generated Largely based on code generated by an AI or LLM label Jun 4, 2026

chatgpt-codex-connector Bot reviewed Jun 4, 2026

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dougqh added comp: core Tracer core type: enhancement Enhancements and improvements tag: performance Performance related changes labels Jun 4, 2026

amarziali reviewed Jun 8, 2026

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dougqh and others added 3 commits June 9, 2026 13:02

Trim verbose generated comments in InternalTagsAdder per review feedback

c773ba7

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

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Pre-construct TagMap.Entry objects in InternalTagsAdder#11555

Pre-construct TagMap.Entry objects in InternalTagsAdder#11555
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