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redis-operator.md

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Redis-pmem operator

This readme describes a complete example to deploy a Redis cluster through the redis-operator using QEMU-emulated persistent memory devices.

Prerequisites

PMEM-CSI installation

Install PMEM-CSI using one of the supported install methods. The next steps assume that there is a pmem-csi-sc-ext4 storage class.

Redis operator installation and Redis cluster deployment

The steps to install the Redis operator by Spotahome are listed below:

  1. Install the Redis operator and validate that the CRD was properly defined: 
    $ kubectl create -f https://raw.githubusercontent.com/spotahome/redis-operator/master/example/operator/all-redis-operator-resources.yaml

$ kubectl get po
NAME                             READY   STATUS    RESTARTS   AGE
pmem-csi-controller-0            3/3     Running   0          134m
pmem-csi-node-c82p5              2/2     Running   0          133m
pmem-csi-node-dwws2              2/2     Running   0          134m
pmem-csi-node-kj7gs              2/2     Running   0          134m
redisoperator-688f6f4fcc-lv5h5   1/1     Running   0          7m29s

$ kubectl get crd
NAME                                     CREATED AT
csidrivers.csi.storage.k8s.io            2019-06-21T16:55:46Z
csinodeinfos.csi.storage.k8s.io          2019-06-21T16:55:47Z
redisfailovers.databases.spotahome.com   2019-06-21T19:03:36Z
  2. Deploy a Redis cluster that uses PMEM-CSI: 
    $ kubectl create -f https://raw.githubusercontent.com/spotahome/redis-operator/master/example/redisfailover/pmem.yaml

$ kubectl get po
NAME                                      READY   STATUS    RESTARTS   AGE
pmem-csi-controller-0                     3/3     Running   0          145m
pmem-csi-node-c82p5                       2/2     Running   0          144m
pmem-csi-node-dwws2                       2/2     Running   0          145m
pmem-csi-node-kj7gs                       2/2     Running   0          145m
redisoperator-688f6f4fcc-lv5h5            1/1     Running   0          18m
rfr-redisfailover-pmem-0                  1/1     Running   0          9m37s
rfr-redisfailover-pmem-1                  1/1     Running   0          6m28s
rfr-redisfailover-pmem-2                  1/1     Running   0          3m15s
rfs-redisfailover-pmem-7595857d4c-56mmz   1/1     Running   0          9m37s
rfs-redisfailover-pmem-7595857d4c-c69xg   1/1     Running   0          9m37s
rfs-redisfailover-pmem-7595857d4c-cqx4p   1/1     Running   0          9m37s
    Note: These steps deploy a Redis cluster with three Redis and three sentinel instances as it is shown when executing kubectl get po command. The provided persistent volumes use the specifications in the persistentVolumeClaim section of example/redisfailover/pmem.yaml, i.e.: 100Mi of storage. Feel free to play around with the numbers of instances to be deployed at example/redisfailover/pmem.yaml.

Verify that the Redis instances are using the volumes provided

First, match the volumes claim name used by each Redis instance to the current pvc which is provisioned by pmem-csi-sc-ext4. Both items must be properly bound. Next, check the block devices in the worker nodes of your Kubernetes cluster and match the ones under the pmem block device, as shown below.

$ kubectl get pvc
NAME                                               STATUS   VOLUME                                     CAPACITY   ACCESS MODES   STORAGECLASS       AGE
redisfailover-pmem-data-rfr-redisfailover-pmem-0   Bound    pvc-82ee55fc-9458-11e9-bec2-0242ac110004   100Mi      RWO            pmem-csi-sc-ext4   19m
redisfailover-pmem-data-rfr-redisfailover-pmem-1   Bound    pvc-f3a04c91-9458-11e9-bec2-0242ac110004   100Mi      RWO            pmem-csi-sc-ext4   16m
redisfailover-pmem-data-rfr-redisfailover-pmem-2   Bound    pvc-668ec3c6-9459-11e9-bec2-0242ac110004   100Mi      RWO            pmem-csi-sc-ext4   13m

$ kubectl exec rfr-redisfailover-pmem-0 -- df /data
Filesystem                                                   1K-blocks  Used Available Use% Mounted on
/dev/ndbus0region0fsdax/8999c281-9458-11e9-8866-a611eaeb0cd9     95088    72     87848   1% /data

$ kubectl exec rfr-redisfailover-pmem-0 -- mount | grep /data
/dev/ndbus0region0fsdax/8999c281-9458-11e9-8866-a611eaeb0cd9 on /data type ext4 (rw,relatime,dax,stripe=256)

Playing around with Redis operator

The steps to start playing around with Redis cluster through sentinel instances managed by the operator, are listed below:

  1. Get the network information of the Redis node working as a master. You can use any sentinel instance, i.e.: 
    $ kubectl exec -it rfs-redisfailover-pmem-7595857d4c-56mmz -- redis-cli -p 26379 SENTINEL get-master-addr-by-name mymaster
1) "10.244.3.4"
2) "6379"
  2. Set a key:value pair into Redis master: 
    $ kubectl exec -it rfs-redisfailover-pmem-7595857d4c-c69xg -- redis-cli -h 10.244.3.4 -p 6379 SET hello world!
OK
  3. Get value from key: 
    $ kubectl exec -it rfs-redisfailover-pmem-7595857d4c-c69xg -- redis-cli -h 10.244.3.4 -p 6379 GET hello
"world!"
  4. Feel free to play around with the Redis cluster.

High availability for Redis instances

In order to ensure high availability for Redis instances, it's required to use hardAntiAffinity: True and storageClassName: pmem-csi-sc-late-binding under Redis deployment specification, i.e.:

apiVersion: databases.spotahome.com/v1
kind: RedisFailover
metadata:
  name: redisfailover-pmem-lb
spec:
  sentinel:
    replicas: 3
    ...
  redis:
    hardAntiAffinity: True
    replicas: 3
    ...
    storage:
      persistentVolumeClaim:
        metadata:
          name: redisfailover-pmem-data
        spec:
          accessModes:
            - ReadWriteOnce
          resources:
            requests:
              storage: 100Mi
          storageClassName: pmem-csi-sc-late-binding

The deployment can be done in the same way as mentioned before, i.e.:

$ kubectl create -f /path/to/pmem-lb.yaml
redisfailover.databases.spotahome.com/redisfailover-pmem-lb created

$ kubectl get po -o custom-columns=NAME:.metadata.name,STATUS:.status.phase,NODE:.spec.nodeName,IP:.status.podIP
NAME                                         STATUS    NODE                          IP
pmem-csi-controller-0                        Running   pmem-csi-clear-govm-worker3   10.244.3.2
pmem-csi-node-l8d58                          Running   pmem-csi-clear-govm-worker3   172.17.0.5
pmem-csi-node-v8cb4                          Running   pmem-csi-clear-govm-worker2   172.17.0.4
pmem-csi-node-xwk2l                          Running   pmem-csi-clear-govm-worker1   172.17.0.3
redisoperator-688f6f4fcc-l6p4f               Running   pmem-csi-clear-govm-worker1   10.244.2.2
rfr-redisfailover-pmem-lb-0                  Running   pmem-csi-clear-govm-worker2   10.244.1.3
rfr-redisfailover-pmem-lb-1                  Running   pmem-csi-clear-govm-worker1   10.244.2.4
rfr-redisfailover-pmem-lb-2                  Running   pmem-csi-clear-govm-worker3   10.244.3.4
rfs-redisfailover-pmem-lb-5c455d7974-9twjz   Running   pmem-csi-clear-govm-worker1   10.244.2.3
rfs-redisfailover-pmem-lb-5c455d7974-dscmx   Running   pmem-csi-clear-govm-worker2   10.244.1.2
rfs-redisfailover-pmem-lb-5c455d7974-jtznn   Running   pmem-csi-clear-govm-worker3   10.244.3.3

As it is shown, each rfr-redisfailover-pmem-lb-X gets assigned to a different Kubernetes cluster node pmem-csi-clear-govm-workerX, where X ∈ {1,2,3}.