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Update README.md with more details on lifecycle state in IMDS mode #1117

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Jan 14, 2025
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Update README.md with more details on lifecycle state in IMDS mode #1117

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9 changes: 7 additions & 2 deletions README.md
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Expand Up @@ -48,13 +48,17 @@ Both modes (IMDS and Queue Processor) monitor for events affecting your EC2 inst
- Webhook feature to send shutdown or restart notification messages
- Unit & integration tests

### Instance Metadata Service Processor
### Instance Metadata Service (IMDS) Processor
Must be deployed as a Kubernetes **DaemonSet**.

- Monitors EC2 Instance Metadata for:
- [Spot Instance Termination Notifications](https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/spot-instance-termination-notices.html)
- [Scheduled Events](https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/monitoring-instances-status-check_sched.html)
- [Instance Rebalance Recommendations](https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/rebalance-recommendations.html)
- [Autoscaling Group Target Lifecycle State changes](https://docs.aws.amazon.com/autoscaling/ec2/userguide/retrieving-target-lifecycle-state-through-imds.html)

#### IMDS Processor with ASG Target Lifecycle State change
Please note that IMDS does **not** support lifecycle *hooks*, but it does support lifecycle *state* change. When using IMDS mode with the ASG target lifecycle state, ASG will update instance metadata to be **Terminated** before it terminates the node. NTH will monitor the path latest/meta-data/autoscaling/target-lifecycle-state for changes and will cordon and drain when the target state is set to **Terminated**.

### Queue Processor
Must be deployed as a Kubernetes **Deployment**. Also requires some **additional infrastructure setup** (including SQS queue, EventBridge rules).
Expand Down Expand Up @@ -84,7 +88,8 @@ When using the EC2 Console or EC2 API to terminate the instance, a state-change
| Scheduled Events | ✅ | ✅ |
| Instance Rebalance Recommendation | ✅ | ✅ |
| ASG Termination Lifecycle Hooks | ❌ | ✅ |
| AZ Rebalance Recommendation | ❌ | ✅ |
| ASG Termination Lifecycle State Change | ✅ | ❌ |
| AZ Rebalance Recommendation | ❌ | ✅ |
| Instance State Change Events | ❌ | ✅ |

### Kubernetes Compatibility
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