[OTEL-1720] Add an API in pkg/trace/stats that converts eligible OTLP spans to the input to APM stats concentrator

[songy23]

What does this PR do?

Add an API OTLPTracesToConcentratorInputs in pkg/trace/stats that converts eligible OTLP spans to the input to APM stats concentrator.

This new API is only expected to be used in datadog connector for now.

Motivation

• Avoid overhead of initializing the whole trace-agent processing pipelines to just get APM stats in datadog connector
• Provide a simplified and more efficient API for OTLP spans to get APM stats.

Describe how to test/QA your changes

Starts a trace agent programmatically and call the new API OTLPTracesToConcentratorInputs with some OTLP traces, then check the APM stats show up in your Org as expected. E.g.

cfg := config.New()
cfg.Endpoints = []*config.Endpoint{
    {
        APIKey: os.Getenv("DD_API_KEY"),
        Host: "datadoghq.com",
    },
  }
// ... and your other configs
statsd := &statsd.NoOpClient{}    
a := agent.NewAgent(ctx, cfg, telemetry.NewNoopCollector(), statsd)

trace := genOTLPTraces() // create some OTLP traces
inputs := stats.OTLPTracesToConcentratorInputs(traces, cfg, nil)
for _, input := range inputs {
  a.Concentrator..Add(input)
}

[pr-commenter]

Regression Detector

Regression Detector Results

Run ID: 3725f509-a34e-4acf-8c80-9556408c9149
Baseline: be8177a
Comparison: 3d4186b

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

No significant changes in experiment optimization goals

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

There were no significant changes in experiment optimization goals at this confidence level and effect size tolerance.

Fine details of change detection per experiment

perf	experiment	goal	Δ mean %	Δ mean % CI
➖	tcp_syslog_to_blackhole	ingress throughput	+5.09	[-16.61, +26.78]
➖	idle	memory utilization	+0.55	[+0.50, +0.59]
➖	uds_dogstatsd_to_api_cpu	% cpu utilization	+0.23	[-2.71, +3.18]
➖	trace_agent_msgpack	ingress throughput	+0.01	[-0.01, +0.02]
➖	trace_agent_json	ingress throughput	+0.00	[-0.01, +0.01]
➖	otel_to_otel_logs	ingress throughput	+0.00	[-0.37, +0.37]
➖	uds_dogstatsd_to_api	ingress throughput	-0.01	[-0.21, +0.19]
➖	tcp_dd_logs_filter_exclude	ingress throughput	-0.03	[-0.06, +0.01]
➖	file_tree	memory utilization	-1.26	[-1.37, -1.15]
➖	pycheck_1000_100byte_tags	% cpu utilization	-1.34	[-5.87, +3.19]
➖	basic_py_check	% cpu utilization	-2.06	[-4.87, +0.75]

Explanation

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:

1. Its estimated |Δ mean %| ≥ 5.00%, indicating the change is big enough to merit a closer look.

2. 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.

3. Its configuration does not mark it "erratic".

[pr-commenter]

Test changes on VM

Use this command from test-infra-definitions to manually test this PR changes on a VM:

inv create-vm --pipeline-id=35227988 --os-family=ubuntu

[brett0000FF]

Looks good from Docs for the release note.

[songy23]

Chatted offline, I'm going to try split this PR into incremental ones as it is currently too large.

[dd-devflow]

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[songy23]

/merge

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[pr-commenter]

Benchmarks

Benchmark execution time: 2024-05-28 12:54:40

Comparing candidate commit 3d4186b in PR branch yang.song/otlp-apm-stats with baseline commit be8177a in branch main.

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

[dd-devflow]

⚠️ MergeQueue

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[songy23]

/merge

[dd-devflow]

🚂 MergeQueue

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Note: if you pushed new commits since the last approval, you may need additional approval.
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[songy23]

/merge -c

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[songy23]

/merge

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