[PROCS-3838] Add handling for ECS Fargate misconfiguration during chunking

[daniel-taf]

What does this PR do?

This PR handles the issue described in #22940. Previously, when on ECS Fargate with a misconfigured pidMode setting, the process agent can fails to maintain the relationship between chunks and props in the ChunkAllocator when calling appendContainerWithoutProcesses causing a panic when props is accessed during ChunkAllocator.Accept. Now, ChunkAllocator.Accept is used directly in the function to that props and chunks remain equal in length.

Motivation

PROCS-3838

Additional Notes

The added unit test confirmed the behavior as it results in a panic on main but passes with this PR's changes.

Possible Drawbacks / Trade-offs

Describe how to test/QA your changes

Run the agent as a sidecar container with container on ECS Fargate without pidMode set. Verify the panic no longer occurs and the log warning appears. Also check that process/container data is available on Datadog.

Sample task definition to create service from:

{
    "containerDefinitions": [
            {
                "name": "redis",
                "image": "redis:latest",
                "cpu": 0,
                "portMappings": [],
                "essential": true,
                "environment": [],
                "mountPoints": [],
                "volumesFrom": [],
                "dockerLabels": {
                    "com.datadoghq.ad.check_names": "[\"redisdb\"]",
                    "com.datadoghq.ad.init_configs": "[{}]",
                    "com.datadoghq.ad.instances": "[{\"host\": \"%%host%%\", \"port\": 6379}]"
                },
                "systemControls": []
            },
            {
                "name": "datadog-agent",
                "image": "public.ecr.aws/datadog/agent:latest",
                "cpu": 0,
                "portMappings": [],
                "essential": true,
                "environment": [
                    {
                        "name": "ECS_FARGATE",
                        "value": "true"
                    },
                    {
                        "name": "DD_PROCESS_AGENT_PROCESS_COLLECTION_ENABLED",
                        "value": "true"
                    }
                ],
                "mountPoints": [],
                "volumesFrom": [],
                "secrets": [
                    {
                        "name": "DD_API_KEY",
                        "valueFrom": "<secret>"
                    }
                ],
               ...
            }
        ],
}

Log:

2024-04-25 20:06:47 UTC | PROCESS | WARN | (pkg/process/checks/chunking.go:25 in chunkProcessesBySizeAndWeight) | No processes found for container , pidMode may not be configured correctly (set to task)	

[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=32974728 --os-family=ubuntu

[pr-commenter]

Regression Detector

Regression Detector Results

Run ID: 30e15658-bf7d-4390-beda-f5d09e92e43d
Baseline: b1ac697
Comparison: 192ac7e

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.

Experiments ignored for regressions

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

perf	experiment	goal	Δ mean %	Δ mean % CI
✅	file_to_blackhole	% cpu utilization	-14.31	[-18.59, -10.03]

Fine details of change detection per experiment

perf	experiment	goal	Δ mean %	Δ mean % CI
➖	basic_py_check	% cpu utilization	+1.71	[-0.82, +4.23]
➖	pycheck_1000_100byte_tags	% cpu utilization	+0.90	[-3.91, +5.72]
➖	idle	memory utilization	+0.53	[+0.49, +0.57]
➖	process_agent_standard_check	memory utilization	+0.36	[+0.30, +0.41]
➖	uds_dogstatsd_to_api_cpu	% cpu utilization	+0.32	[-2.54, +3.18]
➖	process_agent_standard_check_with_stats	memory utilization	+0.28	[+0.22, +0.34]
➖	tcp_dd_logs_filter_exclude	ingress throughput	+0.02	[-0.03, +0.07]
➖	trace_agent_json	ingress throughput	+0.00	[-0.01, +0.01]
➖	trace_agent_msgpack	ingress throughput	-0.00	[-0.01, +0.00]
➖	uds_dogstatsd_to_api	ingress throughput	-0.01	[-0.21, +0.20]
➖	otel_to_otel_logs	ingress throughput	-0.06	[-0.42, +0.30]
➖	process_agent_real_time_mode	memory utilization	-0.30	[-0.35, -0.25]
➖	tcp_syslog_to_blackhole	ingress throughput	-6.39	[-27.21, +14.42]
✅	file_to_blackhole	% cpu utilization	-14.31	[-18.59, -10.03]

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".

[cswatt]

just a grammar suggestion on the changelog

approving so I don't block merge

[daniel-taf]

/merge

[dd-devflow]

🚂 MergeQueue

Pull request added to the queue.

This build is going to start soon! (estimated merge in less than 23m)

Use /merge -c to cancel this operation!

[daniel-taf]

/merge --cancel

[dd-devflow]

⚠️ MergeQueue

This merge request build was cancelled

If you need support, contact us on Slack #devflow!

[daniel-taf]

/merge

[dd-devflow]

🚂 MergeQueue

Pull request added to the queue.

This build is going to start soon! (estimated merge in less than 23m)

Use /merge -c to cancel this operation!