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how to use nodegroup doc

Signed-off-by: wuyue <wuyue_andrew@outlook.com>

how to use nodegroup doc

how to use nodegroup doc

Signed-off-by: wuyue <wuyue_andrew@outlook.com>

how to use nodegroup doc

Signed-off-by: wuyue <wuyue_andrew@outlook.com>
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# Nodegroup Plugin User Guide

## Introduction

**Nodegroup plugin** is designed to isolate resources by assigning labels to nodes and set node label affinty on Queue.

## Usage

### assign label to node
Assign label to node, label key is `volcano.sh/nodegroup-name`.
```shell script
kubectl label nodes <nodename> volcano.sh/nodegroup-name=<groupname>
```

### configure queue
Create queue and bind nodegroup to it.

```yaml
apiVersion: scheduling.volcano.sh/v1beta1
kind: Queue
metadata:
name: default
spec:
reclaimable: true
weight: 1
affinity: # added field
nodeGroupAffinity:
requiredDuringSchedulingIgnoredDuringExecution:
- <groupname>
preferredDuringSchedulingIgnoredDuringExecution:
- <groupname>
nodeGroupAntiAffinity:
requiredDuringSchedulingIgnoredDuringExecution:
- <groupname>
preferredDuringSchedulingIgnoredDuringExecution:
- <groupname>
```
### submit a vcjob
submit vcjob job-1 to default queue.
```shell script
$ cat <<EOF | kubectl apply -f -
apiVersion: batch.volcano.sh/v1alpha1
kind: Job
metadata:
name: job-1
spec:
minAvailable: 1
schedulerName: volcano
queue: default
policies:
- event: PodEvicted
action: RestartJob
tasks:
- replicas: 1
name: nginx
policies:
- event: TaskCompleted
action: CompleteJob
template:
spec:
containers:
- command:
- sleep
- 10m
image: nginx:latest
name: nginx
resources:
requests:
cpu: 1
limits:
cpu: 1
restartPolicy: Never
EOF
```

### validate queue affinity and antiAffinity rules is effected

Query pod information and verify whether the pod has been assigned to the correct node.

```shell script
kubectl get po job-1-nginx-0 -o wide
```

## How the Nodegroup Plugin Works

The nodegroup design document provides the most detailed information about the node group. There are some tips to help avoid certain issues.These tips are based on a four-nodes cluster and vcjob called job-1:

| Node | Label |
| ------ | ------ |
| node1 | groupname1 |
| node2 | groupname2 |
| node3 | groupname3 |
| node4 | groupname4 |

```yaml
apiVersion: batch.volcano.sh/v1alpha1
kind: Job
metadata:
name: job-1
spec:
minAvailable: 1
schedulerName: volcano
queue: default
policies:
- event: PodEvicted
action: RestartJob
tasks:
- replicas: 1
name: nginx
policies:
- event: TaskCompleted
action: CompleteJob
template:
spec:
containers:
- command:
- sleep
- 10m
image: nginx:latest
name: nginx
resources:
requests:
cpu: 1
limits:
cpu: 1
restartPolicy: Never
```
1. Soft constraints are a subset of hard constraints, including both affinity and anti-affinity. Consider a queue setup as follows:
```yaml
apiVersion: scheduling.volcano.sh/v1beta1
kind: Queue
metadata:
name: default
spec:
reclaimable: true
weight: 1
affinity: # added field
nodeGroupAffinity:
requiredDuringSchedulingIgnoredDuringExecution:
- groupname1
- gropuname2
preferredDuringSchedulingIgnoredDuringExecution:
- groupname1
nodeGroupAntiAffinity:
requiredDuringSchedulingIgnoredDuringExecution:
- groupname3
- gropuname4
preferredDuringSchedulingIgnoredDuringExecution:
- groupname3
```
This implies that tasks in the "default" queue will be scheduled on "groupname1" and "groupname2", with a preference for "groupname1" to run first. Tasks are restricted from running on "groupname3" and "groupname4". However, if the resources in other node groups are insufficient, the task can run on "nodegroup3".
2. If soft constraints do not form a subset of hard constraints, the queue configuration is incorrect, leading to tasks running on "groupname2":
```yaml
apiVersion: scheduling.volcano.sh/v1beta1
kind: Queue
metadata:
name: default
spec:
reclaimable: true
weight: 1
affinity: # added field
nodeGroupAffinity:
requiredDuringSchedulingIgnoredDuringExecution:
- gropuname2
preferredDuringSchedulingIgnoredDuringExecution:
- groupname1
nodeGroupAntiAffinity:
requiredDuringSchedulingIgnoredDuringExecution:
- gropuname4
preferredDuringSchedulingIgnoredDuringExecution:
- groupname3
```
3. If there is a conflict between nodeGroupAffinity and nodeGroupAntiAffinity, nodeGroupAntiAffinity takes higher priority.
```yaml
apiVersion: scheduling.volcano.sh/v1beta1
kind: Queue
metadata:
name: default
spec:
reclaimable: true
weight: 1
affinity: # added field
nodeGroupAffinity:
requiredDuringSchedulingIgnoredDuringExecution:
- groupname1
- gropuname2
preferredDuringSchedulingIgnoredDuringExecution:
- groupname1
nodeGroupAntiAffinity:
requiredDuringSchedulingIgnoredDuringExecution:
- groupname1
preferredDuringSchedulingIgnoredDuringExecution:
- gropuname2
```
This implies that tasks in the "default" queue can only run on "groupname2".
4. Generally, tasks run on "groupname1" first because it is a soft constraint. However, the scoring function comprises several plugins, so the task may sometimes run on "groupname2".
```yaml
apiVersion: scheduling.volcano.sh/v1beta1
kind: Queue
metadata:
name: default
spec:
reclaimable: true
weight: 1
affinity: # added field
nodeGroupAffinity:
requiredDuringSchedulingIgnoredDuringExecution:
- groupname1
- gropuname2
preferredDuringSchedulingIgnoredDuringExecution:
- groupname1
nodeGroupAntiAffinity:
requiredDuringSchedulingIgnoredDuringExecution:
- groupname3
- gropuname4
preferredDuringSchedulingIgnoredDuringExecution:
- groupname3
```

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