spinifex/docs/placement-groups

title, description, category, tags, resources

title	description	category	tags	resources
Placement Groups	Create and manage spread and cluster placement groups for hardware-level instance placement control.	Compute	ec2 placement spread cluster	title url Spinifex Repository https://github.com/mulgadc/spinifex title url AWS Placement Groups https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/placement-groups.html

Placement Groups

Create and manage spread and cluster placement groups for hardware-level instance placement control.

Table of Contents

• Overview
• Create
• Launch Into a Placement Group
• Describe
• Delete
• Troubleshooting
  • InsufficientInstanceCapacity Error
  • Cannot Delete Placement Group

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Overview

Placement groups control how Spinifex distributes instances across physical hosts. Two strategies are supported:

• Spread — One instance per physical host, maximising fault isolation
• Cluster — All instances on the same host, minimising latency

The partition strategy is not supported.

Supported operations:

• create-placement-group — Create a new group
• describe-placement-groups — Query groups with optional filters
• delete-placement-group — Remove an empty group

Instructions

Prerequisites

Ensure the AWS profile is set:

export AWS_PROFILE=spinifex

Create

aws ec2 create-placement-group \
  --group-name my-spread-group \
  --strategy spread

aws ec2 create-placement-group \
  --group-name my-cluster-group \
  --strategy cluster

Launch Into a Placement Group

aws ec2 run-instances \
  --image-id $SPINIFEX_AMI \
  --instance-type t3.small \
  --key-name spinifex-key \
  --placement GroupName=my-spread-group \
  --count 3

Describe

aws ec2 describe-placement-groups
aws ec2 describe-placement-groups --group-names my-spread-group
aws ec2 describe-placement-groups --group-ids pg-abc123
aws ec2 describe-placement-groups \
  --filters Name=strategy,Values=spread

Delete

The group must have no running instances before it can be deleted:

aws ec2 terminate-instances --instance-ids $INSTANCE_ID
aws ec2 delete-placement-group --group-name my-spread-group

Troubleshooting

InsufficientInstanceCapacity Error

Not enough distinct physical hosts for a spread launch. Reduce --count or terminate existing instances to free host slots:

spx admin nodes list

Cannot Delete Placement Group

The group still has running instances. Terminate them first:

aws ec2 describe-instances \
  --filters Name=placement-group-name,Values=my-spread-group
aws ec2 terminate-instances --instance-ids $INSTANCE_ID