Implementing High Availability for Applications in CCE
Basic Principles
To achieve high availability for your CCE containers, you can do as follows:
- Deploy three master nodes for the cluster.
- Create nodes in different AZs. When nodes are deployed across AZs, you can customize scheduling policies based on your requirements to maximize resource utilization.
- Create multiple node pools in different AZs and use them for node scaling.
- Set the number of pods to be greater than 2 when creating a workload.
- Set pod affinity rules to distribute pods to different AZs and nodes.
Procedure
Assume that there are four nodes in a cluster distributed in different AZs.
$ kubectl get node -L topology.kubernetes.io/zone,kubernetes.io/hostname NAME STATUS ROLES AGE VERSION ZONE HOSTNAME 192.168.5.112 Ready <none> 42m v1.21.7-r0-CCE21.11.1.B007 zone01 192.168.5.112 192.168.5.179 Ready <none> 42m v1.21.7-r0-CCE21.11.1.B007 zone01 192.168.5.179 192.168.5.252 Ready <none> 37m v1.21.7-r0-CCE21.11.1.B007 zone02 192.168.5.252 192.168.5.8 Ready <none> 33h v1.21.7-r0-CCE21.11.1.B007 zone03 192.168.5.8
Create workloads according to the following podAntiAffinity rules:
- Pod anti-affinity in an AZ. Configure the parameters as follows:
- weight: A larger weight value indicates a higher priority of scheduling. In this example, set it to 50.
- topologyKey: includes a default or custom key for the node label that the system uses to denote a topology domain. A topology key determines the scope where the pod should be scheduled to. In this example, set this parameter to topology.kubernetes.io/zone, which is the label for identifying the AZ where the node is located.
- labelSelector: Select the label of the workload to realize the anti-affinity between this container and the workload.
- The second one is the pod anti-affinity in the node hostname. Configure the parameters as follows:
- weight: Set it to 50.
- topologyKey: Set it to kubernetes.io/hostname.
- labelSelector: Select the label of the pod, which is anti-affinity with the pod.
kind: Deployment
apiVersion: apps/v1
metadata:
name: nginx
namespace: default
spec:
replicas: 2
selector:
matchLabels:
app: nginx
template:
metadata:
labels:
app: nginx
spec:
containers:
- name: container-0
image: nginx:alpine
resources:
limits:
cpu: 250m
memory: 512Mi
requests:
cpu: 250m
memory: 512Mi
affinity:
podAntiAffinity:
preferredDuringSchedulingIgnoredDuringExecution:
- weight: 50
podAffinityTerm:
labelSelector: # Select the label of the workload to realize the anti-affinity between this container and the workload.
matchExpressions:
- key: app
operator: In
values:
- nginx
namespaces:
- default
topologyKey: topology.kubernetes.io/zone # It takes effect in the same AZ.
- weight: 50
podAffinityTerm:
labelSelector: # Select the label of the workload to realize the anti-affinity between this container and the workload.
matchExpressions:
- key: app
operator: In
values:
- nginx
namespaces:
- default
topologyKey: kubernetes.io/hostname # It takes effect on the node.
imagePullSecrets:
- name: default-secret
Create a workload and view the node where the pod is located.
$ kubectl get pod -owide NAME READY STATUS RESTARTS AGE IP NODE nginx-6fffd8d664-dpwbk 1/1 Running 0 17s 10.0.0.132 192.168.5.112 nginx-6fffd8d664-qhclc 1/1 Running 0 17s 10.0.1.133 192.168.5.252
Increase the number of pods to 3. The pod is scheduled to another node, and the three nodes are in three different AZs.
$ kubectl scale --replicas=3 deploy/nginx
deployment.apps/nginx scaled
$ kubectl get pod -owide
NAME READY STATUS RESTARTS AGE IP NODE
nginx-6fffd8d664-8t7rv 1/1 Running 0 3s 10.0.0.9 192.168.5.8
nginx-6fffd8d664-dpwbk 1/1 Running 0 2m45s 10.0.0.132 192.168.5.112
nginx-6fffd8d664-qhclc 1/1 Running 0 2m45s 10.0.1.133 192.168.5.252
Increase the number of pods to 4. The pod is scheduled to the last node. With podAntiAffinity rules, pods can be evenly distributed to AZs and nodes.
$ kubectl scale --replicas=4 deploy/nginx
deployment.apps/nginx scaled
$ kubectl get pod -owide
NAME READY STATUS RESTARTS AGE IP NODE
nginx-6fffd8d664-8t7rv 1/1 Running 0 2m30s 10.0.0.9 192.168.5.8
nginx-6fffd8d664-dpwbk 1/1 Running 0 5m12s 10.0.0.132 192.168.5.112
nginx-6fffd8d664-h796b 1/1 Running 0 78s 10.0.1.5 192.168.5.179
nginx-6fffd8d664-qhclc 1/1 Running 0 5m12s 10.0.1.133 192.168.5.252
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