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High availability

KubeBlocks integrates the official Redis Sentinel solution to realize high availability and adopts Noop as the switch policy.

Redis Sentinel is the high availability solution for a Redis Replication Cluster, which is recommended by Redis and is also the main-stream solution in the community.

In the RedisReplication Cluster provided by KubeBlocks, Sentinel is deployed as an independent component.

Before you start

  • Install KubeBlocks.

  • Create a Redis Replication Cluster.

  • Check the Switch Policy and the role probe.

    • Check whether the switch policy is Noop.

      kubectl get cluster redis-cluster -o yaml
      >
      spec:
      componentSpecs:
      - name: redis
      componentDefRef: redis
      switchPolicy:
      type: Noop
    • Check whether the following role probe parameters exist to verify the role probe is enabled.

      kubectl get cd redis -o yaml
      >
      probes:
      roleProbe:
      failureThreshold: 3
      periodSeconds: 2
      timeoutSeconds: 1

Steps

  1. View the initial status of the Redis cluster.

    kbcli cluster describe redis-cluster

    Redis cluster original status

    Currently, redis-cluster-redis-0 is the primary pod and redis-cluster-redis-1 is the secondary pod.

  2. Simulate a primary pod exception.

    # Enter the primary pod
    kubectl exec -it redis-cluster-redis-0 -- bash

    # Execute the debug sleep command to simulate a primary pod exception
    root@redis-redis-0:/# redis-cli debug sleep 30
  3. Open the Redis Sentinel log to view the failover.

    kubectl logs redis-cluster-redis-sentinel-0

    In the logs, we can view when a high-availability switch occurs.

    1:X 18 Apr 2023 06:13:17.072 # +switch-master redis-cluster-redis-sentinel redis-cluster-redis-0.redis-cluster-redis-headless.default.svc 6379 redis-cluster-redis-1.redis-cluster-redis-headless.default.svc 6379
    1:X 18 Apr 2023 06:13:17.074 * +slave slave redis-cluster-redis-0.redis-cluster-redis-headless.default.svc:6379 redis-cluster-redis-0.redis-cluster-redis-headless.default.svc 6379 @ redis-cluster-redis-sentinel redis-cluster-redis-1.redis-cluster-redis-headless.default.svc 6379
    1:X 18 Apr 2023 06:13:17.077 * Sentinel new configuration saved on disk
  4. Connect to the Redis cluster to view the primary pod information after the exception simulation.

    kbcli cluster connect redis-cluster
    # View the current primary pod
    127.0.0.1:6379> info replication

    Redis info replication

    From the output, redis-cluster-redis-1 has been assigned as the primary's pod.

  5. Describe the cluster and check the instance role.

    kbcli cluster describe redis-cluster

    Redis cluster status after HA

    After the failover, redis-cluster-redis-0 becomes the secondary pod and redis-cluster-redis-1 becomes the primary pod.