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Hyperpod Nccl

AWS LabsOfficialPublished by AWS Labs

  • Skill
  • Review and audit
  • Software development
  • Apache-2.0
  • Low risk
  • Has scripts

From the author

Diagnose NCCL failures and adjacent training-pod failures on HyperPod GPU clusters (EKS or Slurm) — training hangs, AllReduce / collective-op timeouts, EFA or libfabric errors, rendezvous failures, EFA TCP fallback, /dev/shm or memlock issues, NCCL version mismatch across pods, container OOM / exit-137 / OOMKilled, GPU OOM (CUDA out of memory), CrashLoopBackOff / Pending pods, MASTER_ADDR DNS, NetworkPolicy blocking. Not for single-node hardware faults (→ hyperpod-node-debugger § G) or cluster-creation EFA / SSM failures (→ hyperpod-cluster-debugger § A / § F).
— the description by AWS Labs

AutoGineer summary

Written by AutoGineer from the skill’s own files, not by the author

The hyperpod-nccl skill provides a structured, read-only diagnostic workflow for identifying and resolving NCCL and training-pod failures on SageMaker HyperPod clusters (EKS or Slurm). It uses a diagnostic script to analyze infrastructure state, pod logs, and network configurations, mapping identified issues to specific remediation procedures in the provided documentation. The skill emphasizes safe, non-destructive investigation, requiring user approval for any suggested remediation commands.

What it does

  • Automates the collection of cluster, region, and job-specific diagnostic data.
  • Identifies common NCCL failures including timeouts, rendezvous issues, and EFA errors.
  • Detects pod-level issues such as OOMKilled, container crashes, and DNS resolution failures.
  • Maps detected failures to specific, actionable remediation sections in the documentation.
  • Provides a standardized process for escalating unresolved issues to AWS Support.
  • Supports both EKS and Slurm orchestrators with environment-specific diagnostic checks.

When to use it

  • When training jobs hang or experience collective-op timeouts.
  • When encountering EFA, libfabric, or network-related communication errors.
  • When pods fail to start or enter CrashLoopBackOff states.
  • When investigating GPU-related errors like CUDA out of memory or hardware faults.
  • When troubleshooting rendezvous or NCCL version mismatch issues across pods.

Advantages

  • Provides a systematic, read-only approach to complex distributed training debugging.
  • Reduces manual effort by automatically mapping log patterns to known fixes.
  • Ensures safe operations by requiring user approval for all suggested commands.
  • Integrates with existing HyperPod documentation for consistent troubleshooting.
  • Facilitates efficient escalation to AWS Support with pre-formatted diagnostic bundles.

Usage examples

“Run a diagnostic on my EKS HyperPod cluster named 'my-cluster' in 'us-west-2' for a specific job.”
The agent executes the diagnostic script scoped to the provided cluster, region, and job, outputting a list of findings with references to remediation guides.
“I am seeing NCCL timeouts on my Slurm cluster. How do I investigate?”
The agent guides you to run the diagnostic script with the --orchestrator slurm flag and provides instructions on how to interpret the [FAIL] results using the remediation index.

Install

  1. Download the skill as a ZIP:

    https://autogineer.com/agent-skills/awslabs/hyperpod-nccl/download
  2. Unzip it into the cross-client skills folder of your project:

    mkdir -p .agents/skills && unzip hyperpod-nccl.zip -d .agents/skills

Documentation by AWS Labs

HyperPod NCCL Debugger

Operating policy. Run read-only diagnostics yourself. Never run a command that changes cluster, node, or workload state — present each one as a Suggested command (run this yourself) block and wait for the customer. Destructive order: investigate → reboot → replace (replace destroys root + secondary volumes; not supported on Slurm controller nodes). Never discard training state on speculation.

Diagnose NCCL failures on SageMaker HyperPod (EKS and Slurm). scripts/nccl-diagnose.sh reads state via AWS APIs, kubectl, and SSM, then prints each issue as [FAIL] ... → references/<file>.md § <section>. Read-only.

Signal sourcing: list-cluster-events carries infrastructure-level state only (lifecycle, bootstrap, EFA health check, capacity, replacement, reboot, AMI rollback). It does not carry NCCL timeouts, GPU XID/ECC, or per-pod training signals — those come from pod logs, CloudWatch training streams, on-node SSM probes, and NCCL env audit. "No events" on a training-time NCCL issue is expected, not a clean bill of health.


Workflow

  1. Collect cluster name, region, namespace/job (EKS), exact NCCL error string.

  2. Run the diagnostic (always — the output drives everything else).

  3. For every [FAIL] line, Read the referenced section.

  4. Present finding, root cause, and the Suggested-command block with concrete values (instance IDs, SG IDs, namespaces) filled in from the script output. Wait for customer approval.

  5. Re-run the diagnostic to confirm.

If a finding has no matching section, report it as a bug — do not invent a fix.

Step 1: Authenticate kubectl (EKS)

EKS_ARN=$(aws sagemaker describe-cluster --cluster-name <HYPERPOD-NAME> --region <REGION> \
  --query 'Orchestrator.Eks.ClusterArn' --output text)
EKS_NAME=$(echo "$EKS_ARN" | awk -F'/' '{print $NF}')
aws eks update-kubeconfig --name "$EKS_NAME" --region <REGION>
kubectl get nodes

Step 2: Run the diagnostic

# Basic:
bash scripts/nccl-diagnose.sh --cluster <HYPERPOD-NAME> --region <REGION>

# Scope to an EKS job/namespace:
bash scripts/nccl-diagnose.sh --cluster <NAME> --region <REGION> --namespace <NS> --job <JOB>

# Force orchestrator:
bash scripts/nccl-diagnose.sh --cluster <NAME> --region <REGION> --orchestrator slurm

# Larger hardware sample (default 3):
bash scripts/nccl-diagnose.sh --cluster <NAME> --region <REGION> --sample-nodes 10

# Specific node only:
bash scripts/nccl-diagnose.sh --cluster <NAME> --region <REGION> --node i-0abc123def456

Tags: [PASS] · [FAIL] (counted in Issues Found, has reference pointer) · [WARN] · [INFO]. Priorities: P0 blocks training · P1 degraded · P2 informational.


Remediation index

Each [FAIL] line in the script already points directly at the right section. This table is a lookup for manual triage.

FindingSection
SG missing inbound/outbound self-referenceoperations.md § 8
Blocking NetworkPolicy / allow-all missingoperations.md § 8
Slurm node DOWN / DRAINING / RemoveIPCoperations.md § 7
GPU XID / SYSTEM_ERROR / hardware faulthyperpod-node-debugger § F / § G
GPU row-remap / DCGM Fail / silent NaNshyperpod-node-debugger § G.1.a/b
NCCL timeout / rendezvous / stragglerdebugging-guide.md § 1
EFA configuration / not useddebugging-guide.md § 6
EFA TCP fallback (NET/OFI Using TCP)debugging-guide.md § 13
NCCL version mismatch across podsdebugging-guide.md § 10
Container OOM (pod killed, exit 137)debugging-guide.md § 4
GPU OOM (CUDA out of memory)debugging-guide.md § 11
RDMA memlock / /dev/shm too smalldebugging-guide.md § 17
MASTER_ADDR DNS / headless Servicedebugging-guide.md § 12
NVLS / PXN / topology tuningdebugging-guide.md § 19
Any NCCL / EFA / rendezvous log patternerror-patterns-quick-ref.md
Performance / nccl-tests / bandwidthperformance-testing.md

Prerequisites

  • aws CLI v2.13+ authenticated (aws sts get-caller-identity)

  • jq, python3, bash 4.2+

  • unbuffer (from the expect package: yum install expect / apt install expect)

  • kubectl authenticated to the EKS cluster (K8s checks skipped if absent)

  • session-manager-plugin for on-node hardware checks

Defaults

  • Region — required: pass --region or set $AWS_DEFAULT_REGION.

  • Orchestrator — auto-detected; override with --orchestrator eks|slurm.

  • Namespace / job (EKS) — all namespaces; scope with --namespace <NS> --job <JOB>.

  • Hardware sampling — 3 nodes over SSM (capped at 50). --node <ID> for a specific node. Node probes run serially (180 s per node): --sample-nodes 10 can take ~30 min.

  • CloudWatch window — last 2 hours.

  • Colors — auto-disabled on non-TTY or TERM=dumb.

Error handling

FailureScriptTell the customer
aws sts get-caller-identity failsExit 1 with the AWS error"Fix AWS credentials and rerun."
describe-cluster AccessDeniedWarn, add Missing IAM for sagemaker:DescribeCluster"Grant sagemaker:DescribeCluster (operations.md § 2)."
Cluster not foundExit 1 after listing region's clusters"Confirm HyperPod cluster name and region."
kubectl absent / unauthenticatedWarn, skip K8s checks"aws eks update-kubeconfig --name <EKS> --region <R>."
SSM plugin absentWarn, skip on-node hardware checks"Install session-manager-plugin."
SSM times out (180s)Partial output, mark node unreachable"Rerun with --node <ID> --sample-nodes 1; check SSM agent on the node."
CloudWatch log group not foundSkip CloudWatch scan"Enable CloudWatch on the cluster (operations.md § 4)."
Cluster events API throttledWarn, continue with partial data"Rerun later — script is idempotent."

Exit codes: 0 diagnostic complete · 1 fatal prerequisite missing or cluster unreachable.

IAM permissions

Full policy + RBAC in operations.md § 2. SSM on HyperPod uses start-session against sagemaker-cluster:<cluster-id>_<group>-<iid> targets — grant ssm:StartSession / ssm:TerminateSession, not ssm:SendCommand.

Scale strategy

ScopeMethodCoverage
All nodessagemaker:ListClusterNodes (paginated)100% nodes
All K8s objectskubectl100% pods/nodes/policies
HardwareSSM --sample-nodes N (default 3)Sampled
Node logsCloudWatch100% nodes

Large clusters: the PyTorch NCCL backend defaults to a 10-minute collective-op timeout (per the PyTorch distributed docs). Large clusters routinely exceed that on first rendezvous; raise it via torch.distributed.init_process_group(timeout=timedelta(seconds=<N>)). HyperPod support has also observed NCCL topology-graph-search hangs on 256+ node clusters when memlock is unlimited; using a large fixed memlock (e.g. 8388608) in pod securityContext or /etc/security/limits.conf has cleared these in field cases. This memlock pattern is a field observation, not AWS- or NCCL-documented behavior.

For FSDP, DeepSpeed, or Megatron-LM tuning: debugging-guide.md § 18.

Skill delegation

NeedUse
Cluster creation / deployment failureshyperpod-cluster-debugger (§ A / B / C / H + --validate)
Post-deployment cluster-wide managementhyperpod-cluster-debugger
Per-node issues (disk, lifecycle, hardware)hyperpod-node-debugger
Trainium/Inferentia collective-comm (AWS Neuron Collectives, not NCCL)hyperpod-node-debugger § G.2
Shell on nodeshyperpod-ssm
Version comparison across nodeshyperpod-version-checker
Diagnostic bundle for AWS Supporthyperpod-issue-report
MFU / performance degradationhyperpod-mfu-debugger

Escalate to AWS Support

Escalate when:

  1. All SG rules correct, EFA verified on-node, but NCCL still times out.

  2. Hardware checks pass on all nodes but AllReduce still hangs.

  3. Issues Found: 0 but training still fails.

  4. GPU XID errors persist after node replacement.

  5. Collective-op timeout raised and memlock workaround applied but large-cluster rendezvous still hangs.

Before opening the case
# 1. Cluster identity + status
aws sagemaker describe-cluster --cluster-name <C> --region <R>

# 2. Full NCCL diagnostic (sample more nodes for escalation)
bash scripts/nccl-diagnose.sh --cluster <C> --region <R> --sample-nodes 10 > nccl-diag.txt

# 3. Per-node log/config bundle to S3 (delegates to hyperpod-issue-report)
#    See skills/hyperpod-issue-report/SKILL.md for the exact invocation.
Include in the case
  • Cluster name + ARN and AWS region

  • Orchestrator (EKS or Slurm) and EKS cluster name / Slurm controller node

  • Timestamp window (UTC start / end) of the failure

  • Exact NCCL / libfabric error strings (copy verbatim from pod logs or journalctl)

  • Affected instance IDs / node names / pod names / namespace / job name

  • nccl-diag.txt from step 2 above

  • S3 URI of the hyperpod-issue-report bundle from step 3

  • NCCL env vars in effect (printenv | grep -E '^NCCL|^FI_|^TORCH_' from one pod)

References

Files

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Requirements and compatibility

Works with: Claude Code, Claude apps, OpenAI Codex, GitHub Copilot, Cursor, Gemini CLI, Kiro, OpenCode, Goose, Amp, Roo Code, JetBrains Junie, Factory Droid, Devin (ex-Windsurf), Mistral Vibe, OpenHands, Letta

“Works with” means the tool reads the open Agent Skills format; a skill written for one tool may use features others lack.

Needs: Needs a command-line tool, Needs Python, Needs Node.js

Security

What our scanner noticed· Low risk

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Attribution and licence

Published by
AWS Labs
Publisher
AWS Labs (Official)
Source
awslabs/agent-plugins · plugins/sagemaker-ai/skills/hyperpod-nccl · commit fbefb37
Licence
Apache License 2.0 (redistribution allowed)
  • LICENSE (added by AutoGineer from LICENSE)
  • NOTICE (added by AutoGineer from NOTICE)
  • ATTRIBUTION.md (written by AutoGineer)
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