[lvaroqui]

Add an opt-in otel feature to codspeed and codspeed-divan-compat that exports the tracing spans and events emitted by benchmarks over OTLP/HTTP.

With the feature enabled, divan::main() installs a global tracing subscriber when CODSPEED_OTEL_ENDPOINT is set, and flushes the spans when the run ends. CODSPEED_OTEL_FILTER takes EnvFilter directives to select what is exported, and defaults to info. Nothing changes when the variable is unset or the feature is off; all the OpenTelemetry dependencies are optional.

Benchmarks that already set their own global subscriber are left untouched. They can add divan::otel::layer() to it instead, as documented in the README.

Worth a careful look:

• Spans emitted by the exporter's own HTTP stack (hyper, reqwest, opentelemetry_*, …) are always filtered out. Exporting them would create more spans, in an endless loop.
• The OpenTelemetry service name is the bench executable name, with the hash cargo appends to it stripped.

benches/otel_example.rs emits nested spans and events, and a debug span that the default filter drops. Point it at any OTLP/HTTP receiver to check the output:

CODSPEED_OTEL_ENDPOINT=http://localhost:4318 cargo bench -p codspeed-divan-compat --features otel --bench otel_example

Closes COD-3862

[codspeed]

Merging this PR will regress 18 benchmarks

⚠️ 61 benchmarks measured no execution time

Nothing ran under measurement, usually because the compiler removed the code under test. These results are not comparable, so they count as unchanged.

Preventing compiler optimizations

• tsc (aarch64)
• small_drop
• "*benchmark/" '
• iter
• iter_with_large_setup
• iter_batched_ref_large_input
• iter_with_large_drop
• iter_batched_large_input
• iter_batched_small_input
• iter_batched_ref_small_input
• …and 51 more

⚠️ 9 benchmarks spent significant time in system calls

System calls cannot be consistently instrumented, so they are not included in the measure, which understates the real cost. Please switch to the Walltime instrument to accurately measure system calls.

Measurement and system calls

• iter_manual_simple
• recursive_memoized[HashMap<u64, u64>, 0]
• print_env_hello
• fibo_recursive_cached
• allocate
• bench_large_input_local
• bench_large_input
• system_time
• instant

⚠️ Different runtime environments detected

Some benchmarks with significant performance changes were compared across different runtime environments,
which may affect the accuracy of the results.

Open the report in CodSpeed to investigate

⚡ 35 improved benchmarks
❌ 18 regressed benchmarks
✅ 326 untouched benchmarks
⏩ 215 skipped benchmarks¹

Warning

Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
❌	Walltime	generate_combinations[9]	5.7 µs	8.1 µs	-29.93%
❌	Walltime	bench_array2[10]	5 ns	7 ns	-28.57%
❌	Walltime	bench_array1[10]	5 ns	7 ns	-28.57%
❌	Walltime	div	3 ns	4 ns	-25%
❌	CPU Simulation	recursive_memoized[BTreeMap<u64, u64>, 0]	717.2 ns	828.3 ns	-13.41%
❌	Walltime	init_array[1000]	1.5 µs	1.7 µs	-10.46%
❌	Walltime	permutations[6]	68.5 µs	76.4 µs	-10.38%
❌	CPU Simulation	a	568.5 ns	624.1 ns	-8.9%
❌	CPU Simulation	a	568.5 ns	624.1 ns	-8.9%
❌ ⚠️	CPU Simulation	iter_manual_simple	839.4 ns	894.9 ns	-6.21%
❌	CPU Simulation	process_items_with_counter	1.9 µs	2 µs	-5.52%
❌	Walltime	bench_array2[42]	35 ns	37 ns	-5.41%
❌	Walltime	bench_array1[42]	35 ns	37 ns	-5.41%
❌	Walltime	init_array[42]	35 ns	37 ns	-5.41%
❌	Walltime	Iterative[21]	21 ns	22 ns	-4.55%
❌	Walltime	from_elem_decimal[1024]	213 ns	223 ns	-4.48%
❌	Walltime	slice_into_vec_with_bytes	53 ns	55 ns	-3.64%
❌	CPU Simulation	string_copy_with_bytes_counter	1.6 µs	1.7 µs	-3.22%
⚡	Walltime	iterative[0]	4 ns	1 ns	×4
⚡	Walltime	print_env_hello	4.9 µs	1.9 µs	×2.5
...	...	...	...	...	...

ℹ️ Only the first 20 benchmarks are displayed. Go to the app to view all benchmarks.

Tip

Investigate this regression by commenting @codspeedbot fix this regression on this PR, or directly use the CodSpeed MCP with your agent.

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_{Comparing cod-3862-featrust-otel-cargo-feature-in-codspeed-divan-compat (5468bd4) with main (76685ee)}

Footnotes

1. 215 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

[codspeed]

Unable to generate the flamegraphs

The performance report has correctly been generated, but there was an internal error while generating the flamegraphs for this run. We're working on fixing the issue. Feel free to contact us on Discord or at [email protected] if the issue persists.