Assigning Pods to Nodes - Implementing Affinity and Anti-affinity on OKE using Siebel Cloud Manager

Using SCM, you can constrain a pod so that it is restricted to run on particular node(s) or to prefer to run on particular nodes. There are several ways to do this and the recommended approaches all use label selectors to facilitate the selection. Affinity definitions are available in Kubernetes API reference. These can be added as a customization in configuration.

This topic has the following sections:

Customizing the Configuration with Affinity
Use Cases for Making Incremental Changes

Customizing the Configuration with Affinity

Affinity changes will go as a customization that require changes in the SCM repository. Affinity can be defined for the following Siebel pods:

Siebel Server pods (edge, tibus and so on)
Sai Server pods (quantum, alchemist and so on)
cgw pod
smc pod

To add affinity:

SSH into the SCM instance.
Enter commands like the following:
```
docker exec -it cloudmanager bash
```

Override the configuration in different Siebel CR pods:

Edit the /home/opc/siebel/<env_id>/<namespace>-cloud-manager/flux-crm/apps/base/siebel/siebel.yaml file to add "affinity" for each Siebel server/SAI server as:

   sesServer:
   - profile: sieb_server_profile1
     replicas: 1
     siebsrvr_prefix: tibus
     affinity:
       podAffinity:
         requiredDuringSchedulingIgnoredDuringExecution:
         - labelSelector:
             matchExpressions:
             - key: app.siebel.tier
               operator: In
               values:
               - edge
           topologyKey: kubernetes.io/hostname
           weight: 100

  saiServer:
   - profile: ai_automotive_greenfield
     replicas: 1
     sai_prefix: quantum
     affinity:
       nodeAffinity:
         preferredDuringSchedulingIgnoredDuringExecution:
         - weight: 1
         preference:
           matchExpressions:
           - key: topology.kubernetes.io/zone
             operator: In
             values:
             - UK-LONDON-1-AD-1

Edit the /home/opc/siebel/<env_id>/<namespace>-cloud-manager/flux-crm/apps/base/siebel/siebel-gateway.yaml file to add "affinity" for siebel-gateway (CGW) pods:

   cgw:
     replicas: 3
     affinity:
       podAntiAffinity:
         preferredDuringSchedulingIgnoredDuringExecution:
         - weight: 100
           podAffinityTerm:
             labelSelector:
               matchExpressions:
               - key: app.siebel.tier
                 operator: In
                 values:
                 - cgw
             topologyKey: "kubernetes.io/hostname"

Sameway, affinity can also be added to SMC pod by editing /home/opc/siebel/<env_id>/<namespace>-cloud-manager/flux-crm/apps/base/siebel/siebel-gateway.yaml:
```
smc:
     affinity:{} // affinity definition for smc pod goes here
```

Commit your customization in the SCM Git repository. Make sure to add all modified files. The above changes will be included in the initial environment provisioning, where you specify the configuration ID.
Check the status of a requested configuration. For more information, see Checking the Status of a Requested Configuration.
Deploy the environment with the customized configuration. In this step you specify only the configuration ID and the deployment name. For more information, see Deploying Siebel CRM on OCI using Siebel Cloud Manager.

Use Cases for Making Incremental Changes

Here are some use cases for adding affinity definitions to individual Siebel pods.

Adding affinity for individual Siebel Server

Exec into the SCM container:
```
docker exec -it cloudmanager bash
```

Edit: siebel.yaml under /home/opc/siebel/<env_id>/<namespace>-cloud-manager/flux-crm/apps/base/siebel

   sesServer:
   - profile: sieb_server_profile1
     replicas: 1
     siebsrvr_prefix: edge
     affinity:
       nodeAffinity:
         requiredDuringSchedulingIgnoredDuringExecution:
           nodeSelectorTerms:
           - matchExpressions:
             - key: topology.kubernetes.io/zone
               operator: In
               values:
               - UK-LONDON-1-AD-2
         preferredDuringSchedulingIgnoredDuringExecution:
         - weight: 1
           preference:
             matchExpressions:
             - key: another-node-label-key
               operator: In
               values:
               - another-node-label-value

Run the following commands:

git pull
git add .
git commit -m "<message>"
git push

Adding affinity for individual Sai Server

Edit: siebel.yaml under /home/opc/siebel/<env_id>/<namespace>-cloud-manager/flux-crm/apps/base/siebel

   saiServer:
   - profile: application_interface_profile1
     replicas: 1
     sai_prefix: quantum
     affinity:
       nodeAffinity:
         requiredDuringSchedulingIgnoredDuringExecution:
           nodeSelectorTerms:
           - matchExpressions:
             - key: topology.kubernetes.io/zone
               operator: In
               values:
               - UK-LONDON-1-AD-1

Run the following commands:

git pull
git add .
git commit -m "<message>"
git push

Adding affinity for CGW pods

Edit: siebel-gateway.yaml under /home/opc/siebel/<env_id>/<namespace>-cloud-manager/flux-crm/apps/base/siebel
```
   cgw:
     replicas: 3
     affinity: {} // affinity definition for cgw pod goes here.
```

Run the following commands:

git pull
git add .
git commit -m "<message>"
git push

Adding affinity for SMC pod

Edit: siebel-gateway.yaml under /home/opc/siebel/<env_id>/<namespace>-cloud-manager/flux-crm/apps/base/siebel
```
   smc:
     affinity: {} // affinity definition for smc pod goes here.
```

Run the following commands:

git pull
git add .
git commit -m "<message>"
git push