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Customize VPC Internal Load Balancing

The Service provided by Kubernetes can be used for load balancing within the cluster. However, there are several issues with using Service as internal load balancing in customize VPC mode:

  1. The Service IP range is a cluster resource, shared by all customize VPCs, and cannot overlap.
  2. Users cannot set internal load balancing IP addresses according to their own preferences.

To address the above issues, Kube OVN introduced the SwitchLBRule CRD in 1.11, allowing users to set internal load balancing rules within customize VPCs.

SwitchLBRule support the following two ways to set internal load balancing rules within a customize VPC.

Automatically Generate Load Balancing Rules by Selector

Load balancing rules can be generated by selector automatic association with pod configuration through label.

example of SwitchLBRule is as follows:

apiVersion: kubeovn.io/v1
kind: SwitchLBRule
metadata:
  name:  cjh-slr-nginx
spec:
  vip: 1.1.1.1
  sessionAffinity: ClientIP
  namespace: default
  selector:
    - app:nginx
  ports:
  - name: dns
    port: 8888
    targetPort: 80
    protocol: TCP

  ```

- usage of `selector`, `sessionAffinity`, and `port` is the same as Kubernetes Service.
- `vip`：customize load balancing IP address.
- `namespace`：namespace of the `pod` selected by `selector`.

Kube OVN will determine the VPC of the selected `pod` based on the `SwitchLBRule` definition and set the corresponding L2 LB.

## Manually Defined Load Balancing Rules by `Endpoints`

Load balancing rules can be customized configured by   `endpoints`, to support scenarios where load balancing rules cannot be automatically generated through `selector`.  For example, the load balancing backend is `vm` created by `kubevirt`.

example of `SwitchLBRule` is as follows:

```yaml
apiVersion: kubeovn.io/v1
kind: SwitchLBRule
metadata:
  name:  cjh-slr-nginx
spec:
  vip: 1.1.1.1
  sessionAffinity: ClientIP
  namespace: default
  endpoints:
    - 192.168.0.101
    - 192.168.0.102
    - 192.168.0.103
  ports:
  - name: dns
    port: 8888
    targetPort: 80
    protocol: TCP

usage of sessionAffinity, and port is the same as Kubernetes Service.

  • vip：customize load balancing IP address.
  • namespace：namespace of the pod selected by selector.
  • endpoints：load balancing backend IP list.

If both selector and endpoints are configured, the selector configuration will be automatically ignored.

Health Check

OVN supports health checks for load balancer endpoints, for IPv4 load balancers only. When health checks are enabled, the load balancer uses only healthy endpoints.

[Health Checks](https://www.ovn.org/support/dist-docs/ovn-nb.5.html)

Add a health check to SwitchLBRule based on the health check of the ovn load balancer.While creating the SwitchLBRule, obtain a reusable vip from the corresponding VPC and subnet as the detection endpoint and associate the corresponding IP_Port_Mappings and Load_Balancer_Health_Check to the corresponding load balancer.

  • The detection endpoint vip will be automatically determined whether it exists in the corresponding subnet with the same name of the subnet. If it does not exist, it will be automatically created and deleted after all associated SwitchLBRule are deleted.
  • Currently, only SwitchLBRule automatically generated through Selector are supported.

Create SwitchLBRule

root@server:~# kubectl get po -o wide -n vulpecula
NAME                     READY   STATUS    RESTARTS   AGE     IP          NODE     NOMINATED NODE   READINESS GATES
nginx-78d9578975-f4qn4   1/1     Running   3          4d16h   10.16.0.4   worker   <none>           <none>
nginx-78d9578975-t8tm5   1/1     Running   3          4d16h   10.16.0.6   worker   <none>           <none>

# create slr

root@server:~# cat << END > slr.yaml
apiVersion: kubeovn.io/v1
kind: SwitchLBRule
metadata:
  name:  nginx
  namespace:  vulpecula
spec:
  vip: 1.1.1.1
  sessionAffinity: ClientIP
  namespace: default
  selector:
    - app:nginx
  ports:
  - name: dns
    port: 8888
    targetPort: 80
    protocol: TCP
END

root@server:~# kubectl apply -f slr.yaml
root@server:~# kubectl get slr
NAME              VIP       PORT(S)    SERVICE                       AGE
vulpecula-nginx   1.1.1.1   8888/TCP   default/slr-vulpecula-nginx   3d21h

The vip with the same name of the subnet has been created.

# vip for check

root@server:~# kubectl get vip
NAME          NS    V4IP        MAC                 V6IP    PMAC   SUBNET        READY   TYPE
vulpecula-subnet    10.16.0.2   00:00:00:39:95:C1   <nil>          vulpecula-subnet   true

Query the Load_Balancer_Health_Check and Service_Monitor by commands.

root@server:~# kubectl ko nbctl list Load_Balancer
_uuid               : 3cbb6d43-44aa-4028-962f-30d2dba9f0b8
external_ids        : {}
health_check        : [5bee3f12-6b54-411c-9cc8-c9def8f67356]
ip_port_mappings    : {"10.16.0.4"="nginx-78d9578975-f4qn4.default:10.16.0.2", "10.16.0.6"="nginx-78d9578975-t8tm5.default:10.16.0.2"}
name                : cluster-tcp-session-loadbalancer
options             : {affinity_timeout="10800"}
protocol            : tcp
selection_fields    : [ip_src]
vips                : {"1.1.1.1:8888"="10.16.0.4:80,10.16.0.6:80"}

root@server:~# kubectl ko nbctl list Load_Balancer_Health_Check
_uuid               : 5bee3f12-6b54-411c-9cc8-c9def8f67356
external_ids        : {switch_lb_subnet=vulpecula-subnet}
options             : {failure_count="3", interval="5", success_count="3", timeout="20"}
vip                 : "1.1.1.1:8888"

root@server:~# kubectl ko sbctl list Service_Monitor
_uuid               : 1bddc541-cc49-44ea-9935-a4208f627a91
external_ids        : {}
ip                  : "10.16.0.4"
logical_port        : nginx-78d9578975-f4qn4.default
options             : {failure_count="3", interval="5", success_count="3", timeout="20"}
port                : 80
protocol            : tcp
src_ip              : "10.16.0.2"
src_mac             : "c6:d4:b8:08:54:e7"
status              : online

_uuid               : 84dd24c5-e1b4-4e97-9daa-13687ed59785
external_ids        : {}
ip                  : "10.16.0.6"
logical_port        : nginx-78d9578975-t8tm5.default
options             : {failure_count="3", interval="5", success_count="3", timeout="20"}
port                : 80
protocol            : tcp
src_ip              : "10.16.0.2"
src_mac             : "c6:d4:b8:08:54:e7"
status              : online

At this point, the service response can be successfully obtained through load balancer vip.

root@server:~# kubectl exec -it -n vulpecula nginx-78d9578975-t8tm5 -- curl 1.1.1.1:8888
<!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>
<p><em>Thank you for using nginx.</em></p>
</body>
</html>

Update load balance service endpoints

Update the service endpoints of the load balancer by deleting the pod.

kubectl delete po nginx-78d9578975-f4qn4
kubectl get po -o wide -n vulpecula
NAME                     READY   STATUS    RESTARTS   AGE     IP          NODE     NOMINATED NODE   READINESS GATES
nginx-78d9578975-lxmvh   1/1     Running   0          31s     10.16.0.8   worker   <none>           <none>
nginx-78d9578975-t8tm5   1/1     Running   3          4d16h   10.16.0.6   worker   <none>           <none>

Query the Load_Balancer_Health_Check and Service_Monitor by commands, the results have undergone corresponding changes.

root@server:~# kubectl ko nbctl list Load_Balancer
_uuid               : 3cbb6d43-44aa-4028-962f-30d2dba9f0b8
external_ids        : {}
health_check        : [5bee3f12-6b54-411c-9cc8-c9def8f67356]
ip_port_mappings    : {"10.16.0.4"="nginx-78d9578975-f4qn4.default:10.16.0.2", "10.16.0.6"="nginx-78d9578975-t8tm5.default:10.16.0.2", "10.16.0.8"="nginx-78d9578975-lxmvh.default:10.16.0.2"}
name                : cluster-tcp-session-loadbalancer
options             : {affinity_timeout="10800"}
protocol            : tcp
selection_fields    : [ip_src]
vips                : {"1.1.1.1:8888"="10.16.0.6:80,10.16.0.8:80"}

root@server:~# kubectl ko nbctl list Load_Balancer_Health_Check
_uuid               : 5bee3f12-6b54-411c-9cc8-c9def8f67356
external_ids        : {switch_lb_subnet=vulpecula-subnet}
options             : {failure_count="3", interval="5", success_count="3", timeout="20"}
vip                 : "1.1.1.1:8888"

root@server:~# kubectl ko sbctl list Service_Monitor
_uuid               : 84dd24c5-e1b4-4e97-9daa-13687ed59785
external_ids        : {}
ip                  : "10.16.0.6"
logical_port        : nginx-78d9578975-t8tm5.default
options             : {failure_count="3", interval="5", success_count="3", timeout="20"}
port                : 80
protocol            : tcp
src_ip              : "10.16.0.2"
src_mac             : "c6:d4:b8:08:54:e7"
status              : online

_uuid               : 5917b7b7-a999-49f2-a42d-da81f1eeb28f
external_ids        : {}
ip                  : "10.16.0.8"
logical_port        : nginx-78d9578975-lxmvh.default
options             : {failure_count="3", interval="5", success_count="3", timeout="20"}
port                : 80
protocol            : tcp
src_ip              : "10.16.0.2"
src_mac             : "c6:d4:b8:08:54:e7"
status              : online

Delete SwitchLBRule and confirm the resource status, Load_Balancer_Health_Check adn Service_Monitor has been deleted, and the corresponding vip has also been deleted.

root@server:~# kubectl delete -f slr.yaml 
switchlbrule.kubeovn.io "vulpecula-nginx" deleted
root@server:~# kubectl get vip
No resources found
root@server:~# kubectl ko sbctl list Service_Monitor
root@server:~# 
root@server:~# kubectl ko nbctl list Load_Balancer_Health_Check
root@server:~#

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