Hyperpod Nccl
AWS LabsOfficialPublished by AWS Labs
- Skill
- Review and audit
- Software development
- Apache-2.0
- Low risk
- Has scripts
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
Download the skill as a ZIP:
https://mp-staging.autogineer.com/agent-skills/awslabs/hyperpod-nccl/downloadUnzip 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
Collect cluster name, region, namespace/job (EKS), exact NCCL error string.
Run the diagnostic (always — the output drives everything else).
For every
[FAIL]line,Readthe referenced section.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.
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 nodesStep 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-0abc123def456Tags: [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.
| Finding | Section |
|---|---|
| SG missing inbound/outbound self-reference | operations.md § 8 |
| Blocking NetworkPolicy / allow-all missing | operations.md § 8 |
| Slurm node DOWN / DRAINING / RemoveIPC | operations.md § 7 |
| GPU XID / SYSTEM_ERROR / hardware fault | hyperpod-node-debugger § F / § G |
| GPU row-remap / DCGM Fail / silent NaNs | hyperpod-node-debugger § G.1.a/b |
| NCCL timeout / rendezvous / straggler | debugging-guide.md § 1 |
| EFA configuration / not used | debugging-guide.md § 6 |
EFA TCP fallback (NET/OFI Using TCP) | debugging-guide.md § 13 |
| NCCL version mismatch across pods | debugging-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 small | debugging-guide.md § 17 |
| MASTER_ADDR DNS / headless Service | debugging-guide.md § 12 |
| NVLS / PXN / topology tuning | debugging-guide.md § 19 |
| Any NCCL / EFA / rendezvous log pattern | error-patterns-quick-ref.md |
| Performance / nccl-tests / bandwidth | performance-testing.md |
Prerequisites
awsCLI v2.13+ authenticated (aws sts get-caller-identity)jq,python3,bash4.2+unbuffer(from theexpectpackage:yum install expect/apt install expect)kubectlauthenticated to the EKS cluster (K8s checks skipped if absent)session-manager-pluginfor on-node hardware checks
Defaults
Region — required: pass
--regionor 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 10can take ~30 min.CloudWatch window — last 2 hours.
Colors — auto-disabled on non-TTY or
TERM=dumb.
Error handling
| Failure | Script | Tell the customer |
|---|---|---|
aws sts get-caller-identity fails | Exit 1 with the AWS error | "Fix AWS credentials and rerun." |
describe-cluster AccessDenied | Warn, add Missing IAM for sagemaker:DescribeCluster | "Grant sagemaker:DescribeCluster (operations.md § 2)." |
| Cluster not found | Exit 1 after listing region's clusters | "Confirm HyperPod cluster name and region." |
kubectl absent / unauthenticated | Warn, skip K8s checks | "aws eks update-kubeconfig --name <EKS> --region <R>." |
| SSM plugin absent | Warn, 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 found | Skip CloudWatch scan | "Enable CloudWatch on the cluster (operations.md § 4)." |
| Cluster events API throttled | Warn, 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
| Scope | Method | Coverage |
|---|---|---|
| All nodes | sagemaker:ListClusterNodes (paginated) | 100% nodes |
| All K8s objects | kubectl | 100% pods/nodes/policies |
| Hardware | SSM --sample-nodes N (default 3) | Sampled |
| Node logs | CloudWatch | 100% 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
| Need | Use |
|---|---|
| Cluster creation / deployment failures | hyperpod-cluster-debugger (§ A / B / C / H + --validate) |
| Post-deployment cluster-wide management | hyperpod-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 nodes | hyperpod-ssm |
| Version comparison across nodes | hyperpod-version-checker |
| Diagnostic bundle for AWS Support | hyperpod-issue-report |
| MFU / performance degradation | hyperpod-mfu-debugger |
Escalate to AWS Support
Escalate when:
All SG rules correct, EFA verified on-node, but NCCL still times out.
Hardware checks pass on all nodes but AllReduce still hangs.
Issues Found: 0but training still fails.GPU XID errors persist after node replacement.
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.txtfrom step 2 aboveS3 URI of the
hyperpod-issue-reportbundle from step 3NCCL env vars in effect (
printenv | grep -E '^NCCL|^FI_|^TORCH_'from one pod)
References
error-patterns-quick-ref.md — log pattern → code → fix table
debugging-guide.md — per-scenario procedures (21 sections incl. NVLS/PXN/topology)
performance-testing.md — nccl-tests, bandwidth thresholds, straggler detection
operations.md — IAM, SSM format, CloudWatch, env-var reference, node labels, Slurm ops, remediations
Files
- ATTRIBUTION.mdAdded by AutoGineer910 B
- LICENSELicence file added by AutoGineer9.9 KiB
- NOTICELicence file added by AutoGineer89 B
- SKILL.md13.4 KiB
- references/debugging-guide.md47.5 KiB
- references/error-patterns-quick-ref.md10.0 KiB
- references/operations.md18.0 KiB
- references/performance-testing.md9.9 KiB
- scripts/nccl-diagnose.shScript118.6 KiB
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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
- Instructions that use the network
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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)
- Synced
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