feat(stats)!: send telemetry for cardinality limits by VianneyRuhlmann · Pull Request #2159 · DataDog/libdatadog

VianneyRuhlmann · 2026-06-24T16:43:45Z

What does this PR do?

Add telemetry for the collapsed stats group based on this RFC

Motivation

Follow-up of #2158

Additional Notes

Anything else we should know when reviewing?

How to test the change?

Describe here in detail how the change can be validated.

VianneyRuhlmann · 2026-06-24T16:43:58Z

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datadog-prod-us1-4 · 2026-06-24T16:44:35Z

Tests

🎉 All green!

🧪 All tests passed
❄️ No new flaky tests detected

🎯 Code Coverage (details)
• Patch Coverage: 97.80%
• Overall Coverage: 74.17% (+0.10%)

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

🔗 Commit SHA: 883025f | Docs | Datadog PR Page | Give us feedback!}

github-actions · 2026-06-24T16:46:18Z

Clippy Allow Annotation Report

Comparing clippy allow annotations between branches:

Base Branch: origin/main
PR Branch: origin/06-24-feat_stats_send_telemetry_for_cardinality_limits

Summary by Rule

Rule	Base Branch	PR Branch	Change
unwrap_used	3	3	No change (0%)
Total	3	3	No change (0%)

Annotation Counts by File

File	Base Branch	PR Branch	Change
`datadog-sidecar/src/service/stats_flusher.rs`	1	1	No change (0%)
`libdd-data-pipeline/src/otlp/metrics.rs`	1	1	No change (0%)
`libdd-trace-stats/src/stats_exporter.rs`	1	1	No change (0%)

Annotation Stats by Crate

Crate	Base Branch	PR Branch	Change
`clippy-annotation-reporter`	5	5	No change (0%)
`datadog-ffe-ffi`	1	1	No change (0%)
`datadog-ipc`	22	22	No change (0%)
`datadog-live-debugger`	4	4	No change (0%)
`datadog-live-debugger-ffi`	10	10	No change (0%)
`datadog-profiling-replayer`	4	4	No change (0%)
`datadog-sidecar`	45	45	No change (0%)
`libdd-common`	13	13	No change (0%)
`libdd-common-ffi`	12	12	No change (0%)
`libdd-data-pipeline`	6	6	No change (0%)
`libdd-ddsketch`	2	2	No change (0%)
`libdd-dogstatsd-client`	1	1	No change (0%)
`libdd-profiling`	13	13	No change (0%)
`libdd-remote-config`	3	3	No change (0%)
`libdd-telemetry`	20	20	No change (0%)
`libdd-tinybytes`	4	4	No change (0%)
`libdd-trace-normalization`	2	2	No change (0%)
`libdd-trace-obfuscation`	3	3	No change (0%)
`libdd-trace-stats`	1	1	No change (0%)
`libdd-trace-utils`	11	11	No change (0%)
Total	182	182	No change (0%)

About This Report

This report tracks Clippy allow annotations for specific rules, showing how they've changed in this PR. Decreasing the number of these annotations generally improves code quality.

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dd-octo-sts · 2026-06-24T18:52:02Z

Artifact Size Benchmark Report

aarch64-alpine-linux-musl

Artifact	Baseline	Commit	Change
/aarch64-alpine-linux-musl/lib/libdatadog_profiling.so	7.82 MB	7.82 MB	+0% (+24 B) 👌
/aarch64-alpine-linux-musl/lib/libdatadog_profiling.a	85.18 MB	85.24 MB	+.07% (+62.43 KB) 🔍

aarch64-unknown-linux-gnu

Artifact	Baseline	Commit	Change
/aarch64-unknown-linux-gnu/lib/libdatadog_profiling.a	96.32 MB	96.39 MB	+.07% (+71.53 KB) 🔍
/aarch64-unknown-linux-gnu/lib/libdatadog_profiling.so	10.51 MB	10.52 MB	+.05% (+6.25 KB) 🔍

libdatadog-x64-windows

Artifact	Baseline	Commit	Change
/libdatadog-x64-windows/debug/dynamic/datadog_profiling_ffi.dll	25.19 MB	25.21 MB	+.07% (+19.00 KB) 🔍
/libdatadog-x64-windows/debug/dynamic/datadog_profiling_ffi.lib	88.04 KB	88.04 KB	0% (0 B) 👌
/libdatadog-x64-windows/debug/dynamic/datadog_profiling_ffi.pdb	183.52 MB	183.64 MB	+.06% (+120.00 KB) 🔍
/libdatadog-x64-windows/debug/static/datadog_profiling_ffi.lib	939.74 MB	941.39 MB	+.17% (+1.65 MB) 🔍
/libdatadog-x64-windows/release/dynamic/datadog_profiling_ffi.dll	8.23 MB	8.24 MB	+.06% (+5.50 KB) 🔍
/libdatadog-x64-windows/release/dynamic/datadog_profiling_ffi.lib	88.04 KB	88.04 KB	0% (0 B) 👌
/libdatadog-x64-windows/release/dynamic/datadog_profiling_ffi.pdb	24.33 MB	24.36 MB	+.09% (+24.00 KB) 🔍
/libdatadog-x64-windows/release/static/datadog_profiling_ffi.lib	48.52 MB	48.57 MB	+.10% (+52.43 KB) 🔍

libdatadog-x86-windows

Artifact	Baseline	Commit	Change
/libdatadog-x86-windows/debug/dynamic/datadog_profiling_ffi.dll	21.82 MB	21.83 MB	+.06% (+13.50 KB) 🔍
/libdatadog-x86-windows/debug/dynamic/datadog_profiling_ffi.lib	89.42 KB	89.42 KB	0% (0 B) 👌
/libdatadog-x86-windows/debug/dynamic/datadog_profiling_ffi.pdb	187.54 MB	187.66 MB	+.06% (+120.00 KB) 🔍
/libdatadog-x86-windows/debug/static/datadog_profiling_ffi.lib	926.89 MB	928.55 MB	+.17% (+1.65 MB) 🔍
/libdatadog-x86-windows/release/dynamic/datadog_profiling_ffi.dll	6.35 MB	6.36 MB	+.08% (+5.50 KB) 🔍
/libdatadog-x86-windows/release/dynamic/datadog_profiling_ffi.lib	89.42 KB	89.42 KB	0% (0 B) 👌
/libdatadog-x86-windows/release/dynamic/datadog_profiling_ffi.pdb	26.12 MB	26.14 MB	+.08% (+24.00 KB) 🔍
/libdatadog-x86-windows/release/static/datadog_profiling_ffi.lib	46.15 MB	46.20 MB	+.11% (+53.00 KB) 🔍

x86_64-alpine-linux-musl

Artifact	Baseline	Commit	Change
/x86_64-alpine-linux-musl/lib/libdatadog_profiling.a	75.92 MB	75.97 MB	+.06% (+50.32 KB) 🔍
/x86_64-alpine-linux-musl/lib/libdatadog_profiling.so	8.70 MB	8.71 MB	+.09% (+8.03 KB) 🔍

x86_64-unknown-linux-gnu

Artifact	Baseline	Commit	Change
/x86_64-unknown-linux-gnu/lib/libdatadog_profiling.a	91.39 MB	91.44 MB	+.06% (+59.13 KB) 🔍
/x86_64-unknown-linux-gnu/lib/libdatadog_profiling.so	10.59 MB	10.61 MB	+.15% (+16.73 KB) 🔍

# What does this PR do? Add whole-key cardinality limit to the SpanConcentrator. See [this RFC](https://datadoghq.atlassian.net/wiki/spaces/APM/pages/6821151019/PENDING+Cardinality+Limits) for details The telemetry metrics specified in the RFC are implemented in #2159 The per fields limit from the RFC is out of the scope of this PR ## Breaking change The cardinality limit is applied to **all** users of the SpanConcentrator however the limit can be configured manually. # Motivation Avoid unbounded bucket growth when dealing with high cardinality. # Additional Notes ## Limit default value The limit of 7000 entries has been chosen based on the following results **Single Bucket** | Component | Typical | Worst | | --- | --- | --- | | HashMap flat table | 3\.5 MB _(unchanged)_ | 3\.5 MB _(unchanged)_ | | String heap (7 001 × 76 / 122 B) | 0\.5 MB | 0\.9 MB | | DDSketch bins (7 001 × 1 600 / 32 768 B) | 11\.2 MB | 229\.3 MB | | **StatsBucket total** | **~15.2 MB** | **~233.7 MB** | **SpanConcentrator** | Limit | Typical (3 buckets) | Worst (3 buckets) | | --- | --- | --- | | **7 000** | **~45.6 MB** | **~701.2 MB** | ## Trilean change The overflow sentinel key requires us to use a trilean to represent the `is_trace_root` in the aggregation key. Co-authored-by: vianney.ruhlmann <vianney.ruhlmann@datadoghq.com>

gh-worker-devflow-routing-ef8351 · 2026-06-30T14:13:03Z

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github-actions Bot added sidecar data-pipeline labels Jun 24, 2026

This was referenced Jun 24, 2026

feat(stats)!: add whole key cardinality limit #2158

Merged

feat(trace_exporter): enable telemetry in stats exporter #2160

Open

VianneyRuhlmann marked this pull request as ready for review June 24, 2026 17:00

VianneyRuhlmann requested review from a team as code owners June 24, 2026 17:00

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Comment thread libdd-trace-stats/Cargo.toml Outdated

Comment thread libdd-data-pipeline/src/trace_exporter/stats.rs

VianneyRuhlmann force-pushed the 06-24-feat_stats_send_telemetry_for_cardinality_limits branch 2 times, most recently from 98f8c1d to fffe30d Compare June 24, 2026 17:41

VianneyRuhlmann requested a review from a team as a code owner June 24, 2026 17:41

VianneyRuhlmann requested review from mabdinur and removed request for a team June 24, 2026 17:41

VianneyRuhlmann force-pushed the 06-24-feat_stats_add_whole-key_cardinality_limit branch 2 times, most recently from 2655975 to bf5e284 Compare June 24, 2026 17:50

VianneyRuhlmann force-pushed the 06-24-feat_stats_send_telemetry_for_cardinality_limits branch from fffe30d to e5c0f96 Compare June 24, 2026 17:50

VianneyRuhlmann force-pushed the 06-24-feat_stats_add_whole-key_cardinality_limit branch from bf5e284 to ce821ea Compare June 24, 2026 17:59

VianneyRuhlmann force-pushed the 06-24-feat_stats_send_telemetry_for_cardinality_limits branch from e5c0f96 to d97928e Compare June 24, 2026 17:59

VianneyRuhlmann force-pushed the 06-24-feat_stats_add_whole-key_cardinality_limit branch from ce821ea to ebd7e4e Compare June 24, 2026 18:15

VianneyRuhlmann force-pushed the 06-24-feat_stats_send_telemetry_for_cardinality_limits branch from d97928e to c84447e Compare June 24, 2026 18:15

ajgajg1134 reviewed Jun 24, 2026

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Comment thread libdd-trace-stats/src/stats_exporter.rs Outdated

Comment thread libdd-trace-stats/src/stats_exporter.rs Outdated

bantonsson reviewed Jun 25, 2026

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Comment thread libdd-trace-stats/Cargo.toml Outdated

bwoebi reviewed Jun 25, 2026

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Comment thread datadog-sidecar/src/service/stats_flusher.rs

VianneyRuhlmann changed the title ~~feat(stats): send telemetry for cardinality limits~~ feat(stats)!: send telemetry for cardinality limits Jun 26, 2026

VianneyRuhlmann force-pushed the 06-24-feat_stats_send_telemetry_for_cardinality_limits branch 3 times, most recently from 5294954 to b1f49f4 Compare June 29, 2026 14:20

VianneyRuhlmann force-pushed the 06-24-feat_stats_add_whole-key_cardinality_limit branch from ebd7e4e to b04c7f6 Compare June 29, 2026 14:20

VianneyRuhlmann mentioned this pull request Jun 29, 2026

feat(sidecar): enable telemetry for stats #2175

Open

VianneyRuhlmann force-pushed the 06-24-feat_stats_send_telemetry_for_cardinality_limits branch from b1f49f4 to 88317cd Compare June 29, 2026 15:35

VianneyRuhlmann force-pushed the 06-24-feat_stats_add_whole-key_cardinality_limit branch from b04c7f6 to 8d22e4b Compare June 29, 2026 15:35

VianneyRuhlmann force-pushed the 06-24-feat_stats_send_telemetry_for_cardinality_limits branch 2 times, most recently from 23624b6 to a9738ee Compare June 30, 2026 11:58

Base automatically changed from 06-24-feat_stats_add_whole-key_cardinality_limit to main June 30, 2026 14:12

gh-worker-dd-mergequeue-cf854d Bot requested a review from a team as a code owner June 30, 2026 14:12

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gh-worker-dd-devflow-36fce6 Bot added the mergequeue-status: waiting label Jun 30, 2026

feat(stats): send telemetry for cardinality limits

883025f

VianneyRuhlmann force-pushed the 06-24-feat_stats_send_telemetry_for_cardinality_limits branch from a9738ee to 883025f Compare June 30, 2026 14:56

gh-worker-dd-devflow-36fce6 Bot added mergequeue-status: queued mergequeue-status: in_progress mergequeue-status: retrying and removed mergequeue-status: waiting mergequeue-status: queued mergequeue-status: in_progress mergequeue-status: retrying labels Jun 30, 2026

gh-worker-dd-mergequeue-cf854d Bot merged commit a4d4417 into main Jun 30, 2026
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gh-worker-dd-devflow-36fce6 Bot added mergequeue-status: done and removed mergequeue-status: in_progress labels Jun 30, 2026

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feat(stats)!: send telemetry for cardinality limits#2159

feat(stats)!: send telemetry for cardinality limits#2159
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