chore(otlp): use `StringBuilder` in OTLP trace translation #1150

rayz · 2026-02-02T20:06:26Z

Summary

This pr adds StringBuilder to the translator to be used whenever we want to incrementally build a string in the OTLP traces translator logic.

Change Type

Bug fix
New feature
Non-functional (chore, refactoring, docs)
Performance

How did you test this PR?

Existing tests/ci

References

Copilot

Pull request overview

This PR refactors OTLP trace translation code to use StringBuilder instead of format! macro calls for improved performance by reducing string allocations.

Changes:

Added MetaString::from_interner() method to handle string interning with fallback logic
Replaced format! macro usage with StringBuilder for constructing operation names, resource names, and tags
Removed helper functions intern_operation_name and intern_resource_name that are now obsolete

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
lib/stringtheory/src/lib.rs	Added `from_interner()` method and exported `Interner` trait for string interning with fallback
lib/saluki-components/src/common/otlp/traces/translator.rs	Refactored tag construction to use `StringBuilder` instead of `format!`
lib/saluki-components/src/common/otlp/traces/transform.rs	Replaced all `format!` calls and helper functions with `StringBuilder` for operation names, resource names, and attribute key mapping

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Copilot · 2026-02-02T20:07:27Z

lib/saluki-components/src/common/otlp/traces/transform.rs


    let span_kind = SpanKind::try_from(otel_span.kind).unwrap_or(SpanKind::Unspecified);
    let is_client = matches!(span_kind, SpanKind::Client);
    let is_server = matches!(span_kind, SpanKind::Server);


The string_builder is initialized once at the beginning of the function but cleared and reused multiple times across different conditional branches. Consider initializing it closer to where it's first used, or document this reuse pattern, as having it declared at the top with many intervening lines before first use makes the code harder to follow and increases cognitive load.

Suggested change

let is_server = matches!(span_kind, SpanKind::Server);

let is_server = matches!(span_kind, SpanKind::Server);

// NOTE: `string_builder` is intentionally created once and reused (cleared/repopulated)

// across the conditional branches below to avoid repeated allocations.

Copilot · 2026-02-02T20:07:27Z

lib/saluki-components/src/common/otlp/traces/transform.rs

    otel_span: &OtlpSpan, span_attributes: &[KeyValue], resource_attributes: &[KeyValue], interner: &GenericMapInterner,
 ) -> MetaString {
    let span_kind = SpanKind::try_from(otel_span.kind).unwrap_or(SpanKind::Unspecified);
+    let mut string_builder = StringBuilder::new();


Similar to the previous comment, the string_builder is declared at the top of the function but used in multiple conditional branches below. Consider initializing it closer to its first use or adding a comment explaining the reuse pattern to improve code clarity.

pr-commenter · 2026-02-02T20:14:41Z

Binary Size Analysis (Agent Data Plane)

Target: 8e261e7 (baseline) vs 25e29d5 (comparison) diff
Analysis Type: Stripped binaries (debug symbols excluded)
Baseline Size: 26.95 MiB
Comparison Size: 26.95 MiB
Size Change: +360 B (+0.00%)
Pass/Fail Threshold: +5%
Result: PASSED ✅

Changes by Module

Module	File Size	Symbols
`[Unmapped]`	-2.85 KiB	1
`core`	+1.31 KiB	22
`saluki_components::common::otlp`	+934 B	12
`stringtheory::MetaString::from_interner`	+391 B	1
`saluki_components::decoders::otlp`	+311 B	3
`saluki_common::strings::StringBuilder<I>`	+259 B	1
`saluki_common::task::instrument`	+224 B	2
`[sections]`	-149 B	6
`unicode_segmentation`	-56 B	1
`saluki_components::sources::otlp`	+37 B	2
`aho_corasick`	-12 B	1
`std`	-4 B	1
`tokio`	+2 B	29
`agent_data_plane::internal::remote_agent`	+2 B	1
`saluki_core::data_model::event`	+0 B	4

Detailed Symbol Changes

    FILE SIZE        VM SIZE    
 --------------  -------------- 
  [NEW] +25.7Ki  [NEW] +25.6Ki    saluki_components::common::otlp::traces::transform::otel_to_dd_span_minimal::h39a1d2a06d273496
  [NEW] +20.3Ki  [NEW] +20.2Ki    saluki_components::common::otlp::traces::transform::otel_span_to_dd_span::hdac3746e1e67a5aa
  [NEW] +20.2Ki  [NEW] +20.0Ki    _<saluki_common::task::instrument::InstrumentedTask<F> as core::future::future::Future>::poll::h04f74a1200ab9975
  [NEW] +10.9Ki  [NEW] +10.7Ki    <saluki_core::data_model::event::Event as core::clone::Clone>::clone.10329
  [NEW] +6.82Ki  [NEW] +6.69Ki    saluki_components::common::otlp::traces::translator::OtlpTracesTranslator::translate_spans::ha163927cf4d550d3
  [NEW] +2.86Ki  [NEW] +2.72Ki    saluki_components::common::otlp::traces::transform::conditionally_map_otlp_attribute_to_meta::hc7a3626227bf7a73
  [NEW] +2.85Ki  [NEW] +2.70Ki    <saluki_core::data_model::event::metric::value::MetricValues as core::clone::Clone>::clone.10330
  [NEW] +2.18Ki  [NEW] +2.03Ki    core::ptr::drop_in_place<saluki_components::sources::otlp::run_converter::{{closure}}>::h168433b87c3cd9e7
  [NEW] +1.61Ki  [NEW] +1.53Ki    tokio::runtime::task::raw::poll::h0daf1c9ca32ff8b7
  [NEW] +1.55Ki  [NEW] +1.48Ki    tokio::runtime::task::raw::poll::h42809e2d38098459
  -0.1%    -794  -0.1% -1.05Ki    [67 Others]
  [DEL] -1.61Ki  [DEL] -1.53Ki    tokio::runtime::task::raw::poll::had5a00e17d30ec70
  [DEL] -1.97Ki  [DEL] -1.82Ki    core::ptr::drop_in_place<saluki_components::sources::otlp::run_converter::{{closure}}>::h3f1322f670e5b0d0
 -30.2% -2.85Ki  [ = ]       0    [Unmapped]
  [DEL] -2.85Ki  [DEL] -2.70Ki    <saluki_core::data_model::event::metric::value::MetricValues as core::clone::Clone>::clone.10331
  [DEL] -2.88Ki  [DEL] -2.74Ki    saluki_components::common::otlp::traces::transform::conditionally_map_otlp_attribute_to_meta::hcb57765e0e34df90
  [DEL] -6.80Ki  [DEL] -6.67Ki    saluki_components::common::otlp::traces::translator::OtlpTracesTranslator::translate_spans::h810428a59aa97882
  [DEL] -10.9Ki  [DEL] -10.7Ki    <saluki_core::data_model::event::Event as core::clone::Clone>::clone.10330
  [DEL] -20.0Ki  [DEL] -19.8Ki    _<saluki_common::task::instrument::InstrumentedTask<F> as core::future::future::Future>::poll::hc5e1da33e8b4bd56
  [DEL] -20.8Ki  [DEL] -20.6Ki    saluki_components::common::otlp::traces::transform::otel_span_to_dd_span::h00544139f30b5566
  [DEL] -23.3Ki  [DEL] -23.2Ki    saluki_components::common::otlp::traces::transform::otel_to_dd_span_minimal::h914728bafd674b5e
  +0.0%    +360  +0.0% +2.85Ki    TOTAL

pr-commenter · 2026-02-02T20:42:08Z

Regression Detector (Agent Data Plane)

Regression Detector Results

Run ID: 8d41ffc3-ca96-4eb7-bff7-df14be668b87

Baseline: 8e261e7
Comparison: 25e29d5
Diff

❌ Experiments with retried target crashes

This is a critical error. One or more replicates failed with a non-zero exit code. These replicates may have been retried. See Replicate Execution Details for more information.

dsd_uds_100mb_3k_contexts_throughput
otlp_ingest_logs_5mb_cpu
otlp_ingest_logs_5mb_memory
otlp_ingest_logs_5mb_throughput
quality_gates_rss_dsd_ultraheavy

Optimization Goals: ✅ Improvement(s) detected

perf	experiment	goal	Δ mean %	Δ mean % CI	trials	links
✅	otlp_ingest_traces_5mb_cpu	% cpu utilization	-8.07	[-10.65, -5.50]	1	(metrics) (profiles) (logs)

Experiments ignored for regressions

Regressions in experiments with settings containing erratic: true are ignored.

perf	experiment	goal	Δ mean %	Δ mean % CI	trials	links
❌	otlp_ingest_logs_5mb_memory	memory utilization	+17.08	[+16.49, +17.68]	1	(metrics) (profiles) (logs)
➖	otlp_ingest_logs_5mb_cpu	% cpu utilization	+1.53	[-3.74, +6.81]	1	(metrics) (profiles) (logs)
➖	otlp_ingest_logs_5mb_throughput	ingress throughput	+0.02	[-0.11, +0.16]	1	(metrics) (profiles) (logs)

Fine details of change detection per experiment

perf	experiment	goal	Δ mean %	Δ mean % CI	trials	links
❌	otlp_ingest_logs_5mb_memory	memory utilization	+17.08	[+16.49, +17.68]	1	(metrics) (profiles) (logs)
➖	dsd_uds_10mb_3k_contexts_cpu	% cpu utilization	+6.26	[-24.27, +36.79]	1	(metrics) (profiles) (logs)
➖	otlp_ingest_metrics_5mb_memory	memory utilization	+4.55	[+4.29, +4.81]	1	(metrics) (profiles) (logs)
➖	dsd_uds_100mb_3k_contexts_cpu	% cpu utilization	+2.09	[-3.75, +7.92]	1	(metrics) (profiles) (logs)
➖	otlp_ingest_logs_5mb_cpu	% cpu utilization	+1.53	[-3.74, +6.81]	1	(metrics) (profiles) (logs)
➖	dsd_uds_1mb_3k_contexts_cpu	% cpu utilization	+1.20	[-52.10, +54.49]	1	(metrics) (profiles) (logs)
➖	dsd_uds_500mb_3k_contexts_memory	memory utilization	+0.23	[+0.04, +0.42]	1	(metrics) (profiles) (logs)
➖	quality_gates_rss_dsd_ultraheavy	memory utilization	+0.19	[+0.06, +0.33]	1	(metrics) (profiles) (logs)
➖	dsd_uds_512kb_3k_contexts_memory	memory utilization	+0.12	[-0.06, +0.30]	1	(metrics) (profiles) (logs)
➖	quality_gates_rss_idle	memory utilization	+0.12	[+0.08, +0.16]	1	(metrics) (profiles) (logs)
➖	quality_gates_rss_dsd_low	memory utilization	+0.04	[-0.12, +0.20]	1	(metrics) (profiles) (logs)
➖	dsd_uds_1mb_3k_contexts_memory	memory utilization	+0.04	[-0.15, +0.23]	1	(metrics) (profiles) (logs)
➖	dsd_uds_100mb_3k_contexts_throughput	ingress throughput	+0.04	[-0.01, +0.09]	1	(metrics) (profiles) (logs)
➖	otlp_ingest_metrics_5mb_throughput	ingress throughput	+0.03	[-0.10, +0.17]	1	(metrics) (profiles) (logs)
➖	dsd_uds_100mb_3k_contexts_memory	memory utilization	+0.03	[-0.17, +0.23]	1	(metrics) (profiles) (logs)
➖	otlp_ingest_logs_5mb_throughput	ingress throughput	+0.02	[-0.11, +0.16]	1	(metrics) (profiles) (logs)
➖	dsd_uds_512kb_3k_contexts_throughput	ingress throughput	+0.00	[-0.05, +0.06]	1	(metrics) (profiles) (logs)
➖	otlp_ingest_traces_5mb_throughput	ingress throughput	+0.00	[-0.08, +0.08]	1	(metrics) (profiles) (logs)
➖	dsd_uds_1mb_3k_contexts_throughput	ingress throughput	-0.00	[-0.06, +0.06]	1	(metrics) (profiles) (logs)
➖	dsd_uds_10mb_3k_contexts_throughput	ingress throughput	-0.02	[-0.16, +0.13]	1	(metrics) (profiles) (logs)
➖	dsd_uds_10mb_3k_contexts_memory	memory utilization	-0.24	[-0.44, -0.04]	1	(metrics) (profiles) (logs)
➖	quality_gates_rss_dsd_heavy	memory utilization	-0.25	[-0.37, -0.13]	1	(metrics) (profiles) (logs)
➖	quality_gates_rss_dsd_medium	memory utilization	-0.32	[-0.52, -0.13]	1	(metrics) (profiles) (logs)
➖	dsd_uds_500mb_3k_contexts_cpu	% cpu utilization	-0.56	[-1.90, +0.78]	1	(metrics) (profiles) (logs)
➖	dsd_uds_500mb_3k_contexts_throughput	ingress throughput	-0.92	[-1.06, -0.79]	1	(metrics) (profiles) (logs)
➖	dsd_uds_512kb_3k_contexts_cpu	% cpu utilization	-0.97	[-55.88, +53.94]	1	(metrics) (profiles) (logs)
➖	otlp_ingest_metrics_5mb_cpu	% cpu utilization	-1.09	[-6.69, +4.51]	1	(metrics) (profiles) (logs)
➖	otlp_ingest_traces_5mb_memory	memory utilization	-2.43	[-2.68, -2.17]	1	(metrics) (profiles) (logs)
✅	otlp_ingest_traces_5mb_cpu	% cpu utilization	-8.07	[-10.65, -5.50]	1	(metrics) (profiles) (logs)

Bounds Checks: ✅ Passed

perf	experiment	bounds_check_name	replicates_passed	links
✅	quality_gates_rss_dsd_heavy	memory_usage	10/10	(metrics) (profiles) (logs)
✅	quality_gates_rss_dsd_low	memory_usage	10/10	(metrics) (profiles) (logs)
✅	quality_gates_rss_dsd_medium	memory_usage	10/10	(metrics) (profiles) (logs)
✅	quality_gates_rss_dsd_ultraheavy	memory_usage	10/10	(metrics) (profiles) (logs)
✅	quality_gates_rss_idle	memory_usage	10/10	(metrics) (profiles) (logs)

Explanation

Confidence level: 90.00%
Effect size tolerance: |Δ mean %| ≥ 5.00%

Performance changes are noted in the perf column of each table:

✅ = significantly better comparison variant performance
❌ = significantly worse comparison variant performance
➖ = no significant change in performance

A regression test is an A/B test of target performance in a repeatable rig, where "performance" is measured as "comparison variant minus baseline variant" for an optimization goal (e.g., ingress throughput). Due to intrinsic variability in measuring that goal, we can only estimate its mean value for each experiment; we report uncertainty in that value as a 90.00% confidence interval denoted "Δ mean % CI".

For each experiment, we decide whether a change in performance is a "regression" -- a change worth investigating further -- if all of the following criteria are true:

Its estimated |Δ mean %| ≥ 5.00%, indicating the change is big enough to merit a closer look.
Its 90.00% confidence interval "Δ mean % CI" does not contain zero, indicating that if our statistical model is accurate, there is at least a 90.00% chance there is a difference in performance between baseline and comparison variants.
Its configuration does not mark it "erratic".

Replicate Execution Details

We run multiple replicates for each experiment/variant. However, we allow replicates to be automatically retried if there are any failures, up to 8 times, at which point the replicate is marked dead and we are unable to run analysis for the entire experiment. We call each of these attempts at running replicates a replicate execution. This section lists all replicate executions that failed due to the target crashing or being oom killed.

Note: In the below tables we bucket failures by experiment, variant, and failure type. For each of these buckets we list out the replicate indexes that failed with an annotation signifying how many times said replicate failed with the given failure mode. In the below example the baseline variant of the experiment named experiment_with_failures had two replicates that failed by oom kills. Replicate 0, which failed 8 executions, and replicate 1 which failed 6 executions, all with the same failure mode.

Experiment	Variant	Replicates	Failure	Logs	Debug Dashboard
experiment_with_failures	baseline	0 (x8) 1 (x6)	Oom killed		Debug Dashboard

The debug dashboard links will take you to a debugging dashboard specifically designed to investigate replicate execution failures.

❌ Retried Normal Replicate Execution Failures (non-profiling)

Experiment	Variant	Replicates	Failure	Debug Dashboard
dsd_uds_100mb_3k_contexts_throughput	baseline	0	Failed to shutdown when requested	Debug Dashboard
otlp_ingest_logs_5mb_cpu	baseline	4	Failed to shutdown when requested	Debug Dashboard
otlp_ingest_logs_5mb_cpu	comparison	7	Failed to shutdown when requested	Debug Dashboard
otlp_ingest_logs_5mb_memory	baseline	0 (x2)	Failed to shutdown when requested	Debug Dashboard
otlp_ingest_logs_5mb_throughput	comparison	4	Failed to shutdown when requested	Debug Dashboard
quality_gates_rss_dsd_ultraheavy	baseline	6	Failed to shutdown when requested	Debug Dashboard

lib/saluki-components/src/common/otlp/traces/translator.rs

lib/saluki-components/src/common/otlp/traces/transform.rs

Copilot

Pull request overview

Copilot reviewed 6 out of 6 changed files in this pull request and generated 14 comments.

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lib/saluki-components/src/common/otlp/traces/transform.rs

Copilot

Pull request overview

Copilot reviewed 6 out of 6 changed files in this pull request and generated 1 comment.

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Copilot · 2026-02-03T18:11:26Z

lib/stringtheory/src/lib.rs

+    /// The string is inlined if possible. If it cannot be inlined, the interner is tried. If interning fails, an owned
+    /// string is allocated.


The documentation states 'If interning fails, an owned string is allocated,' but the implementation doesn't show a failure case for interning. The try_intern method returns Option<InternedString> where None indicates the string couldn't be interned (likely due to capacity), not a failure. Consider clarifying this as 'If the string cannot be interned, an owned string is allocated' to better reflect the actual behavior.

Suggested change

/// The string is inlined if possible. If it cannot be inlined, the interner is tried. If interning fails, an owned

/// string is allocated.

/// The string is inlined if possible. If it cannot be inlined, the interner is tried. If the string cannot be

/// interned, an owned string is allocated.

Copilot, c'mon dawg. 😂

## Summary  This pr adds `StringBuilder` to the translator to be used whenever we want to incrementally build a string in the OTLP traces translator logic. ## Change Type - [ ] Bug fix - [ ] New feature - [ ] Non-functional (chore, refactoring, docs) - [x] Performance ## How did you test this PR?  Existing tests/ci ## References    eb64b2e

rayz added 7 commits January 30, 2026 12:15

Use MetaString::from_static when possible

8ac2a80

Use interner

b2aaf87

Use interner

032a881

Make interner size configurable

6dc0024

Empty commit, trigger ci

4241aaa

Set interner size to 4MiB in experiments

2fc11d0

Use StringBuilder

cf680a3

Copilot AI review requested due to automatic review settings February 2, 2026 20:06

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lib/saluki-components/src/common/otlp/traces/translator.rs Outdated Show resolved Hide resolved

lib/saluki-components/src/common/otlp/traces/transform.rs Outdated Show resolved Hide resolved

rayz added 2 commits February 2, 2026 16:12

Feedback

4d6e66a

MOre stringbuilder

755a35a

Copilot AI review requested due to automatic review settings February 2, 2026 21:43

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Use new string builder method

08093a8

rayz marked this pull request as ready for review February 3, 2026 18:10

rayz requested a review from a team as a code owner February 3, 2026 18:10

Copilot AI review requested due to automatic review settings February 3, 2026 18:10

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tobz approved these changes Feb 3, 2026

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tobz added the type/chore Updates to dependencies or general "administrative" tasks necessary to maintain the codebase/repo. label Feb 3, 2026

rayz force-pushed the rayz/add-string-interner-to-otlp-trace-translator branch 2 times, most recently from fb6280d to 938e29e Compare February 4, 2026 21:05

rayz changed the base branch from rayz/add-string-interner-to-otlp-trace-translator to main February 5, 2026 19:15

Merge branch 'main' into rayz/otlp-use-stringbuilder

2ea3ba0

dd-octo-sts bot added area/core Core functionality, event model, etc. area/components Sources, transforms, and destinations. area/memory Memory bounds and memory management. labels Feb 5, 2026

dd-octo-sts bot added decoders/otlp OTLP decoder. source/otlp OTLP source. labels Feb 5, 2026

Merge branch 'main' into rayz/otlp-use-stringbuilder

25e29d5

rayz merged commit eb64b2e into main Feb 5, 2026
57 checks passed

		/// The string is inlined if possible. If it cannot be inlined, the interner is tried. If interning fails, an owned
		/// string is allocated.

chore(otlp): use StringBuilder in OTLP trace translation #1150

chore(otlp): use StringBuilder in OTLP trace translation #1150

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Binary Size Analysis (Agent Data Plane)

Changes by Module

Detailed Symbol Changes

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Regression Detector (Agent Data Plane)

Regression Detector Results

❌ Experiments with retried target crashes

Optimization Goals: ✅ Improvement(s) detected

Experiments ignored for regressions

Fine details of change detection per experiment

Bounds Checks: ✅ Passed

Explanation

Replicate Execution Details

❌ Retried Normal Replicate Execution Failures (non-profiling)

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chore(otlp): use `StringBuilder` in OTLP trace translation #1150

chore(otlp): use `StringBuilder` in OTLP trace translation #1150

rayz commented Feb 2, 2026 •

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