How to Run HA Cassandra on IBM Cloud Kubernetes Service

IBM Cloud Kubernetes Service is a managed Kubernetes offering running in IBM Cloud. It is designed to deliver powerful tools, intuitive user experience, and built-in security for rapid delivery of applications that can be bound to cloud services related to IBM Watson, IoT, DevOps and data analytics. As a CNCF certified Kubernetes provider, IBM Cloud Kubernetes Service provides intelligent scheduling, self-healing, horizontal scaling, service discovery and load balancing, automated rollouts and rollbacks, and secret and configuration management. The service also has advanced capabilities around simplified cluster management, container security, and isolation policies, the ability to design a cluster with a custom configuration and integrated operational tools for consistency in deployment.
 
Portworx is a cloud native storage platform to run persistent workloads deployed on a variety of orchestration engines including Kubernetes. With Portworx, customers can manage the database of their choice on any infrastructure using any container scheduler. It provides a single data management layer for all stateful services, no matter where they run.
 
This tutorial is a walk-through of the steps involved in deploying and managing a highly available Cassandra cluster on IBM Cloud Kubernetes Service (IKS).
 
In summary, to run HA Cassandra cluster on IKS you need to:

  • Launch an IKS cluster running on bare metal servers with software-defined storage (SDS)
  • Install cloud native storage solution like Portworx as a daemon set on IKS
  • Create a storage class defining your storage requirements like replication factor, snapshot policy, and performance profile
  • Deploy Cassandra as a StatefulSet on Kubernetes
  • Test failover by killing or cordoning nodes in your cluster
  • Optional – Take an app consistent snapshot of Cassandra
  • Optional – Bootstrap a new Cassandra cluster from snapshot backup

 

Launching an IKS Cluster

For running stateful workloads in a production environment backed by Portworx, it is highly recommended to launch an IKS cluster based on bare metal servers and software-defined storage. The minimum requirements of a worker node to successfully run Portworx include:

  • 4 CPU cores
  • 4GB memory
  • 128GB of raw unformatted storage
  • 10Gbps network speed

 
For details on launching a Kubernetes cluster with bare metal worker nodes, please refer to the documentation of IBM Cloud Kubernetes Service.
 
We are using an IKS cluster with 4 nodes out of which 3 nodes are running bare metal servers with SDS based on the instance type ms2c.4x32.1.9tb.ssd.encrypted. Only these machines that meet the prerequisite would be used by Portworx.
 
$ kubectl get nodes
 
When we filter the nodes based on the label, we see the below nodes:

$ kubectl get nodes -l beta.kubernetes.io/instance-type=ms2c.4x32.1.9tb.ssd.encrypted
NAME           STATUS   ROLES    AGE    VERSION
10.177.26.18   Ready    <none>   4d7h   v1.13.2+IKS
10.185.22.28   Ready    <none>   4d7h   v1.13.2+IKS
10.73.90.131   Ready    <none>   4d3h   v1.13.2+IKS

To exclude nodes that don’t meet Portworx prerequisites, you can apply a label to skip the installation of Portworx. For example, the below command applies a label on the node with name 10.185.22.14 which doesn’t run on a bare metal server.

$ kubectl label nodes 10.185.22.14  px/enabled=false --overwrite

 

Installing Portworx in IKS

Installing Portworx on IKS is not very different from installing it on any other Kubernetes cluster. It is recommended that you create an etcd instance through Compose for etcd. You can use the Helm Chart to install Portworx cluster in IKS. Portworx documentation for IKS has the prerequisites and instructions to install and configure Portworx, STORK, and other components.
 
At the end of the installation, we will have Portworx Daemonset running on the nodes excluding those that are filtered out in the previous step.
 
$ kubectl get pods
 
Once the IKS cluster is up and running, and Portworx is installed and configured, we will deploy a highly available Cassandra database cluster.
 

Creating a storage class for Cassandra

Once the IKS cluster is up and running, and Portworx is installed and configured, we will deploy a highly available Cassandra database.
 
Through storage class objects, an admin can define different classes of Portworx volumes that are offered in a cluster. These classes will be used during the dynamic provisioning of volumes. The storage class defines the replication factor, I/O profile (e.g., for a database or a CMS), and priority (e.g., SSD or HDD). These parameters impact the availability and throughput of workloads and can be specified for each volume. This is important because a production database will have different requirements than a development Jenkins cluster.
 
In this example, the storage class that we deploy has a replication factor of 3 with I/O profile set to “db,” and priority set to “high.” This means that the storage will be optimized for low latency database workloads like Cassandra and automatically placed on the highest performance storage available in the cluster.
 

$ cat > px-cassandra-sc.yaml << EOF
kind: StorageClass
apiVersion: storage.k8s.io/v1
metadata:
  name: px-storageclass
provisioner: kubernetes.io/portworx-volume
parameters:
  repl: "3"
  io_profile: "db"
  priority_io: "high"
  fg: "true"
EOF

Create the storage class and verify its available in the default namespace.

$ kubectl create -f px-cassandra-sc.yaml
storageclass.storage.k8s.io/px-storageclass created

$ kubectl get sc
NAME                         PROVISIONER                     AGE
default                      ibm.io/ibmc-file                8d
ibmc-file-bronze (default)   ibm.io/ibmc-file                8d
ibmc-file-custom             ibm.io/ibmc-file                8d
ibmc-file-gold               ibm.io/ibmc-file                8d
ibmc-file-retain-bronze      ibm.io/ibmc-file                8d
ibmc-file-retain-custom      ibm.io/ibmc-file                8d
ibmc-file-retain-gold        ibm.io/ibmc-file                8d
ibmc-file-retain-silver      ibm.io/ibmc-file                8d
ibmc-file-silver             ibm.io/ibmc-file                8d
portworx-db-sc               kubernetes.io/portworx-volume   19h
portworx-db2-sc              kubernetes.io/portworx-volume   19h
portworx-null-sc             kubernetes.io/portworx-volume   19h
portworx-shared-sc           kubernetes.io/portworx-volume   19h
px-repl3-sc                  kubernetes.io/portworx-volume   41h
px-storageclass              kubernetes.io/portworx-volume   11s
stork-snapshot-sc            stork-snapshot                  19h

 

Deploying Cassandra StatefulSet on IKS

Finally, let’s create a Cassandra cluster as a Kubernetes StatefulSet object. Like a Kubernetes deployment, a StatefulSet manages pods that are based on an identical container spec. Unlike a deployment, a StatefulSet maintains a sticky identity for each of their Pods. For more details on StatefulSets, refer to Kubernetes documentation.
 
A StatefulSet in Kubernetes requires a headless service to provide network identity to the pods it creates. The following command and the spec will help you create a headless service for your Cassandra installation.
 

$ cat > px-cassandra-svc.yaml << EOF
apiVersion: v1
kind: Service
metadata:
  labels:
    app: cassandra
  name: cassandra
spec:
  clusterIP: None
  ports:
    - port: 9042
  selector:
    app: cassandra
EOF
$ kubectl create -f px-cassandra-svc.yaml
service/cassandra created

Now, let’s go ahead and create a StatefulSet running Cassandra cluster based on the below spec.

cat > px-cassandra-app.yaml << EOF
apiVersion: "apps/v1beta1"
kind: StatefulSet
metadata:
  name: cassandra
spec:
  serviceName: cassandra
  replicas: 3
  template:
    metadata:
      labels:
        app: cassandra
    spec:
      schedulerName: stork
      containers:
      - name: cassandra
        image: cassandra:3
        ports:
          - containerPort: 7000
            name: intra-node
          - containerPort: 7001
            name: tls-intra-node
          - containerPort: 7199
            name: jmx
          - containerPort: 9042
            name: cql
        env:
          - name: CASSANDRA_SEEDS
            value: cassandra-0.cassandra.default.svc.cluster.local
          - name: MAX_HEAP_SIZE 
            value: 512M
          - name: HEAP_NEWSIZE
            value: 512M
          - name: CASSANDRA_CLUSTER_NAME
            value: "Cassandra"
          - name: CASSANDRA_DC
            value: "DC1"
          - name: CASSANDRA_RACK
            value: "Rack1"
          - name: CASSANDRA_AUTO_BOOTSTRAP
            value: "false"            
          - name: CASSANDRA_ENDPOINT_SNITCH
            value: GossipingPropertyFileSnitch
        volumeMounts:
        - name: cassandra-data
          mountPath: /var/lib/cassandra
  volumeClaimTemplates:
  - metadata:
      name: cassandra-data
      annotations:
        volume.beta.kubernetes.io/storage-class: px-storageclass
      labels:
         app: cassandra
    spec:
      accessModes: [ "ReadWriteOnce" ]
      resources:
        requests:
          storage: 1Gi
EOF
$ kubectl apply -f px-cassandra-app.yaml
statefulset.apps/cassandra created

Verify that all the pods are in the Running state before proceeding further.

$ kubectl get statefulset
NAME        DESIRED   CURRENT   AGE
cassandra   3         2         45s
$ kubectl get pods
NAME          READY   STATUS    RESTARTS   AGE
cassandra-0   1/1     Running   0          30s
cassandra-1   1/1     Running   0          21s
cassandra-2   1/1     Running   0          11s

 
$ kubectl get pods
 
Let’s also check if persistent volume claims are bound to the volumes.

$ kubectl get pvc
NAME                         STATUS   VOLUME                                     CAPACITY   ACCESS MODES   STORAGECLASS      AGE
cassandra-data-cassandra-0   Bound    pvc-78e2ad08-31e3-11e9-930d-4e511e6b17c9   5Gi        RWO            px-storageclass   2m29s
cassandra-data-cassandra-1   Bound    pvc-7e41a4c6-31e3-11e9-930d-4e511e6b17c9   5Gi        RWO            px-storageclass   2m20s
cassandra-data-cassandra-2   Bound    pvc-840e19eb-31e3-11e9-930d-4e511e6b17c9   5Gi        RWO            px-storageclass   2m10s

Notice the naming convention followed by Kubernetes for the pods and volume claims. The arbitrary number attached to each object indicates the association of pods and volumes.
 
We can now inspect the Portworx volume associated with one of the Cassandra pod by accessing the pxctl tool.

$  VOL=`kubectl get pvc | grep cassandra-0 | awk '{print $3}'`
$ PX_POD=$(kubectl get pods -l name=portworx -n kube-system -o jsonpath='{.items[0].metadata.name}')
$ kubectl exec -it $PX_POD -n kube-system -- /opt/pwx/bin/pxctl volume inspect ${VOL}
Volume	:  113404360113301454
	Name            	 :  pvc-78e2ad08-31e3-11e9-930d-4e511e6b17c9
	Size            	 :  5.0 GiB
	Format          	 :  ext4
	HA              	 :  2
	IO Priority     	 :  LOW
	Creation time   	 :  Feb 16 12:07:47 UTC 2019
	Shared          	 :  no
	Status          	 :  up
	State           	 :  Attached: d7f53ebb-0d02-4ba4-b689-2f335e8f9379 (10.177.26.18)
	Device Path     	 :  /dev/pxd/pxd113404360113301454
	Labels          	 :  namespace=default,pvc=cassandra-data-cassandra-0
	Reads           	 :  13
	Reads MS        	 :  36
	Bytes Read      	 :  53248
	Writes          	 :  1184
	Writes MS       	 :  7612
	Bytes Written   	 :  97746944
	IOs in progress 	 :  0
	Bytes used      	 :  13 MiB
	Replica sets on nodes:
		Set 0
		  Node 		 : 10.73.90.131 (Pool 0)
		  Node 		 : 10.177.26.18 (Pool 0)
	Replication Status	 :  Up
	Volume consumers	 :
		- Name           : cassandra-0 (78e5102c-31e3-11e9-930d-4e511e6b17c9) (Pod)
		  Namespace      : default
		  Running on     : 10.177.26.18
		  Controlled by  : cassandra (StatefulSet)

 
$ kubectl exec -it $PX_POD -n kube-system -- /opt/pwx/bin/pxctl volume inspect ${VOL}
 
The output from the above command confirms the creation of volumes that are backing Cassandra nodes.
 
We can also use Cassandra’s nodetool to check the status of the cluster.

$ kubectl exec cassandra-0 -- nodetool status
Datacenter: DC1
===============
Status=Up/Down
|/ State=Normal/Leaving/Joining/Moving
--  Address         Load       Tokens       Owns (effective)  Host ID                               Rack
UN  172.30.122.147  93.96 KiB  256          62.0%             e271976b-ebc7-47a2-a715-e3c969c132f3  Rack1
UN  172.30.59.96    108.61 KiB  256          69.2%             52d484b9-50a2-401a-b481-b98e66388f86  Rack1
UN  172.30.59.97    177.35 KiB  256          68.7%             58190bc9-f5dc-49c9-abfb-49dacc83df96  Rack1

 
$ kubectl exec cassandra-0 -- nodetool status
 
To get the pods and hosts associated with the Cassandra cluster, run the below command:

$ kubectl get pods -l app=cassandra -o json | jq '.items[] | {"name": .metadata.name,"hostname": .spec.nodeName, "hostIP": .status.hostIP, "PodIP": .status.podIP}'
{
  "name": "cassandra-0",
  "hostname": "10.177.26.18",
  "hostIP": "10.177.26.18",
  "PodIP": "172.30.59.96"
}
{
  "name": "cassandra-1",
  "hostname": "10.73.90.131",
  "hostIP": "10.73.90.131",
  "PodIP": "172.30.122.147"
}
{
  "name": "cassandra-2",
  "hostname": "10.177.26.18",
  "hostIP": "10.177.26.18",
  "PodIP": "172.30.59.97"
}

 

Failing over Cassandra pod on Kubernetes

Populating sample data

Let’s populate the database with some sample data by accessing the first node of the Cassandra cluster. We will do this by invoking Cassandra shell, cqlsh in one of the pods.

$ kubectl exec -it cassandra-0 -- cqlsh
Connected to Cassandra at 127.0.0.1:9042.
[cqlsh 5.0.1 | Cassandra 3.11.3 | CQL spec 3.4.4 | Native protocol v4]
Use HELP for help.
cqlsh>

Now that we are inside the shell, we can create a keyspace and populate it.

CREATE KEYSPACE classicmodels WITH REPLICATION = { 'class' : 'SimpleStrategy', 'replication_factor' : 3 };
	
CONSISTENCY QUORUM;
Consistency level set to QUORUM.

use classicmodels;

CREATE TABLE offices (officeCode text PRIMARY KEY, city text, phone text, addressLine1 text, addressLine2 text, state text, country text, postalCode text, territory text);

INSERT into offices(officeCode, city, phone, addressLine1, addressLine2, state, country ,postalCode, territory) values 
	('1','San Francisco','+1 650 219 4782','100 Market Street','Suite 300','CA','USA','94080','NA');

INSERT into offices(officeCode, city, phone, addressLine1, addressLine2, state, country ,postalCode, territory) values 
	('2','Boston','+1 215 837 0825','1550 Court Place','Suite 102','MA','USA','02107','NA');

INSERT into offices(officeCode, city, phone, addressLine1, addressLine2, state, country ,postalCode, territory) values 	
	('3','NYC','+1 212 555 3000','523 East 53rd Street','apt. 5A','NY','USA','10022','NA');

INSERT into offices(officeCode, city, phone, addressLine1, addressLine2, state, country ,postalCode, territory) values 
	('4','Paris','+33 14 723 4404','43 Rue Jouffroy abbans', NULL ,NULL,'France','75017','EMEA');

INSERT into offices(officeCode, city, phone, addressLine1, addressLine2, state, country ,postalCode, territory) values 		
	('5','Tokyo','+81 33 224 5000','4-1 Kioicho',NULL,'Chiyoda-Ku','Japan','102-8578','Japan');

INSERT into offices(officeCode, city, phone, addressLine1, addressLine2, state, country ,postalCode, territory) values 
	('6','Sydney','+61 2 9264 2451','5-11 Wentworth Avenue','Floor #2',NULL,'Australia','NSW 2010','APAC');

INSERT into offices(officeCode, city, phone, addressLine1, addressLine2, state, country ,postalCode, territory) values 
	('7','London','+44 20 7877 2041','25 Old Broad Street','Level 7',NULL,'UK','EC2N 1HN','EMEA');

INSERT into offices(officeCode, city, phone, addressLine1, addressLine2, state, country ,postalCode, territory) values 
	('8','Mumbai','+91 22 8765434','BKC','Building 2',NULL,'MH','400051','APAC');

Let’s verify that the data is populated.

SELECT * FROM classicmodels.offices;

 officecode | addressline1           | addressline2 | city          | country   | phone            | postalcode | state      | territory
------------+------------------------+--------------+---------------+-----------+------------------+------------+------------+-----------
          6 |  5-11 Wentworth Avenue |     Floor #2 |        Sydney | Australia |  +61 2 9264 2451 |   NSW 2010 |       null |      APAC
          7 |    25 Old Broad Street |      Level 7 |        London |        UK | +44 20 7877 2041 |   EC2N 1HN |       null |      EMEA
          4 | 43 Rue Jouffroy abbans |         null |         Paris |    France |  +33 14 723 4404 |      75017 |       null |      EMEA
          3 |   523 East 53rd Street |      apt. 5A |           NYC |       USA |  +1 212 555 3000 |      10022 |         NY |        NA
          5 |            4-1 Kioicho |         null |         Tokyo |     Japan |  +81 33 224 5000 |   102-8578 | Chiyoda-Ku |     Japan
          8 |                    BKC |   Building 2 |        Mumbai |        MH |   +91 22 8765434 |     400051 |       null |      APAC
          2 |       1550 Court Place |    Suite 102 |        Boston |       USA |  +1 215 837 0825 |      02107 |         MA |        NA
          1 |      100 Market Street |    Suite 300 | San Francisco |       USA |  +1 650 219 4782 |      94080 |         CA |        NA

(8 rows)
cqlsh:classicmodels>

 
cqlsh:classicmodels> SELECT * FROM classic models.offices;
 
Exit from the client shell to return to the host.

You can run the select query by accessing cqlsh from any of the pods of the StatefulSet.

Run nodetool again to check the replication of the data. The below command shows that the hosts on which the row with officecode=6 is available.

$ kubectl exec -it cassandra-0 -- nodetool getendpoints classicmodels offices 6
172.30.122.147
172.30.59.97
172.30.59.96

 

Simulating node failure

Let’s get the node name where the first pod of Cassandra StatefulSet is running.

$ NODE=`kubectl get pods cassandra-0 -o json | jq -r .spec.nodeName`

Now, let’s simulate the node failure by cordoning off the Kubernetes node.

$ kubectl cordon ${NODE}
node/10.177.26.18 cordoned

The above command disabled scheduling on one of the nodes.

$ kubectl get nodes
NAME                                    STATUS                     ROLES    AGE   VERSION
NAME           STATUS                     ROLES    AGE   VERSION
10.177.26.18   Ready,SchedulingDisabled      8d    v1.13.2+IKS
10.185.22.14   Ready                         8d    v1.13.2+IKS
10.185.22.29   Ready                         14h   v1.13.2+IKS
10.73.90.131   Ready                         8d    v1.13.2+IKS

Let’s go ahead and delete the pod cassandra-0 running on the node that is cordoned off.

$ kubectl delete pod cassandra-0
pod "cassandra-0" deleted

Kubernetes controller now tries to create the pod on a different node.

$ kubectl get pods -o wide
NAME          READY   STATUS    RESTARTS   AGE   IP               NODE           NOMINATED NODE   READINESS GATES
cassandra-0   1/1     Running   0          29s   172.30.122.149   10.73.90.131              
cassandra-1   1/1     Running   0          10m   172.30.122.147   10.73.90.131              
cassandra-2   1/1     Running   2          10m   172.30.59.97     10.177.26.18              

Finally, let’s verify that the data is still available.
 

Verifying that the data is intact

Let’s access the data in the first pod of the StatefulSet – cassandra-0.

$ kubectl exec cassandra-0 -- cqlsh -e 'select * from classicmodels.offices'

 officecode | addressline1           | addressline2 | city          | country   | phone            | postalcode | state      | territory
------------+------------------------+--------------+---------------+-----------+------------------+------------+------------+-----------
          6 |  5-11 Wentworth Avenue |     Floor #2 |        Sydney | Australia |  +61 2 9264 2451 |   NSW 2010 |       null |      APAC
          7 |    25 Old Broad Street |      Level 7 |        London |        UK | +44 20 7877 2041 |   EC2N 1HN |       null |      EMEA
          4 | 43 Rue Jouffroy abbans |         null |         Paris |    France |  +33 14 723 4404 |      75017 |       null |      EMEA
          3 |   523 East 53rd Street |      apt. 5A |           NYC |       USA |  +1 212 555 3000 |      10022 |         NY |        NA
          5 |            4-1 Kioicho |         null |         Tokyo |     Japan |  +81 33 224 5000 |   102-8578 | Chiyoda-Ku |     Japan
          8 |                    BKC |   Building 2 |        Mumbai |        MH |   +91 22 8765434 |     400051 |       null |      APAC
          2 |       1550 Court Place |    Suite 102 |        Boston |       USA |  +1 215 837 0825 |      02107 |         MA |        NA
          1 |      100 Market Street |    Suite 300 | San Francisco |       USA |  +1 650 219 4782 |      94080 |         CA |        NA

(8 rows)

Observe that the data is still there and all the content is intact! We can also run the nodetool again to see that the new node is indeed a part of the StatefulSet.

$ kubectl exec cassandra-1 -- nodetool status
Datacenter: DC1
===============
Status=Up/Down
|/ State=Normal/Leaving/Joining/Moving
--  Address         Load       Tokens       Owns (effective)  Host ID                               Rack
UN  172.30.122.149  173.85 KiB  256          100.0%            52d484b9-50a2-401a-b481-b98e66388f86  Rack1
UN  172.30.122.147  111.06 KiB  256          100.0%            e271976b-ebc7-47a2-a715-e3c969c132f3  Rack1
UN  172.30.59.97    197.18 KiB  256          100.0%            58190bc9-f5dc-49c9-abfb-49dacc83df96  Rack1

 

Capturing Application Consistent Snapshots to Restore Data

Portworx enables storage admins to perform backup and restore operations through the snapshots. 3DSnap is a feature to capture application consistent snapshots from multiple nodes of a database cluster. This is highly recommended when running a multi-node Cassandra cluster as a Kubernetes StatefulSet. 3DSnap will create the snapshot from each of the node in the cluster, which ensures that the state is accurately captured from the distributed cluster.
 
3DSnap allows administrators to execute commands just before taking the snapshot and right after completing the task of taking a snapshot. These triggers will ensure that the data is fully committed to the disk before the snapshot. Similarly, it is possible to run a workload-specific command to refresh or force sync immediately after restoring the snapshot.
 
This section will walk you through the steps involved in creating and restoring a 3DSnap for the Cassandra StatefulSet.
 

Creating a 3DSnap

It’s a good idea to flush the data to the disk before initiating the snapshot creation. This is defined through a rule, which is a Custom Resource Definition created by Stork, a Kubernetes scheduler extender and Operator created by Portworx.

$ cat > px-cassandra-rule.yaml << EOF
apiVersion: stork.libopenstorage.org/v1alpha1
kind: Rule
metadata:
  name: px-cassandra-rule
spec:
  - podSelector:
      app: cassandra
    actions:
    - type: command
      value: nodetool flush
EOF

Create the rule from the above YAML file.

$ kubectl create -f px-cassandra-rule.yaml
rule.stork.libopenstorage.org/px-cassandra-rule created

We will now initiate a 3DSnap task to backup all the PVCs associated with the Cassandra pods belonging to the StatefulSet.

$ cat > px-cassandra-snap.yaml << EOF
apiVersion: volumesnapshot.external-storage.k8s.io/v1
kind: VolumeSnapshot
metadata:
  name: cassandra-3d-snapshot
  annotations:
    portworx.selector/app: cassandra
    stork.rule/pre-snapshot: px-cassandra-rule
spec:
  persistentVolumeClaimName: cassandra-data-cassandra-0
EOF
$ kubectl create -f px-cassandra-snap.yaml
volumesnapshot.volumesnapshot.external-storage.k8s.io/cassandra-3d-snapshot created

Let’s now verify that the snapshot creation is successful.

$ kubectl get volumesnapshot
NAME                                                                                    AGE
cassandra-3d-snapshot                                                                   12s
cassandra-3d-snapshot-cassandra-data-cassandra-0-4e98bb3d-31e5-11e9-930d-4e511e6b17c9   2s
cassandra-3d-snapshot-cassandra-data-cassandra-1-4e98bb3d-31e5-11e9-930d-4e511e6b17c9   3s
cassandra-3d-snapshot-cassandra-data-cassandra-2-4e98bb3d-31e5-11e9-930d-4e511e6b17c9   4s
$ kubectl get volumesnapshotdatas
NAME                                                                                    AGE
cassandra-3d-snapshot-cassandra-data-cassandra-0-4e98bb3d-31e5-11e9-930d-4e511e6b17c9   20s
cassandra-3d-snapshot-cassandra-data-cassandra-1-4e98bb3d-31e5-11e9-930d-4e511e6b17c9   21s
cassandra-3d-snapshot-cassandra-data-cassandra-2-4e98bb3d-31e5-11e9-930d-4e511e6b17c9   22s
k8s-volume-snapshot-54976020-31e5-11e9-993d-eaa7125cd4d9                                20s

 
$ kubectl get volumesnapshot
 

Restoring from a 3DSnap

Let’s now restore from the 3DSnap. Before that, we will simulate the database crash by deleting the StatefulSet and associated PVCs.

$ kubectl delete sts cassandra
statefulset.apps "cassandra" deleted
$ kubectl delete pvc -l app=cassandra
persistentvolumeclaim "cassandra-data-cassandra-0" deleted
persistentvolumeclaim "cassandra-data-cassandra-1" deleted
persistentvolumeclaim "cassandra-data-cassandra-2" deleted

Now our Kubernetes cluster has no database running. Let’s go ahead and restore the data from the snapshot before relaunching Cassandra StatefulSet.
 
We will now create three Persistent Volume Claims (PVCs) from existing 3DSnap with exactly the same volume name that the StatefulSet expects. When the pods are created as a part of the StatefulSet, they point to the existing PVCs which are already populated with the data restored from the snapshots.
 
Let’s create three PVCs from the 3DSnap snapshots. Notice how the annotation points to the snapshot in each PVC manifest.

$ cat > px-cassandra-pvc-0.yaml << EOF
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: cassandra-data-cassandra-0
  annotations:
    snapshot.alpha.kubernetes.io/snapshot: "cassandra-3d-snapshot-cassandra-data-cassandra-0-f7ffa638-cdda-11e8-a2f0-061f808edbd0"
spec:
  accessModes:
     - ReadWriteOnce
  storageClassName: stork-snapshot-sc
  resources:
    requests:
      storage: 5Gi
EOF
$ cat > px-cassandra-pvc-1.yaml << EOF
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: cassandra-data-cassandra-1
  annotations:
    snapshot.alpha.kubernetes.io/snapshot: "cassandra-3d-snapshot-cassandra-data-cassandra-0-f7ffa638-cdda-11e8-a2f0-061f808edbd0"
spec:
  accessModes:
     - ReadWriteOnce
  storageClassName: stork-snapshot-sc
  resources:
    requests:
      storage: 5Gi
EOF
$ cat > px-cassandra-pvc-2.yaml << EOF
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: cassandra-data-cassandra-0
  annotations:
    snapshot.alpha.kubernetes.io/snapshot: "cassandra-3d-snapshot-cassandra-data-cassandra-2-f7ffa638-cdda-11e8-a2f0-061f808edbd0"
spec:
  accessModes:
     - ReadWriteOnce
  storageClassName: stork-snapshot-sc
  resources:
    requests:
      storage: 5Gi
EOF

Create the PVCs from the above definitions.

$ kubectl create -f px-cassandra-snap-pvc-0.yaml
persistentvolumeclaim/cassandra-data-cassandra-0 created

$ kubectl create -f px-cassandra-snap-pvc-1.yaml
persistentvolumeclaim/cassandra-data-cassandra-1 created

$ kubectl create -f px-cassandra-snap-pvc-2.yaml
persistentvolumeclaim/cassandra-data-cassandra-2 created

$ kubectl create -f px-cassandra-app.yaml
statefulset.apps/cassandra created

Verify that the new PVCs are ready and bound.

$ kubectl get pvc
NAME                         STATUS   VOLUME                                     CAPACITY   ACCESS MODES   STORAGECLASS        AGE
cassandra-data-cassandra-0   Bound    pvc-23f7a5fa-31e6-11e9-b299-a6db67e221f9   5Gi        RWO            stork-snapshot-sc   47s
cassandra-data-cassandra-1   Bound    pvc-2fd121f8-31e6-11e9-b299-a6db67e221f9   5Gi        RWO            stork-snapshot-sc   27s
cassandra-data-cassandra-2   Bound    pvc-32730d3d-31e6-11e9-aa17-32e4785d9ba0   5Gi        RWO            stork-snapshot-sc   22s

 
$ kubectl get pvc
 
With the PVCs in place, we are ready to launch the StatefulSet with no changes to the YAML file. Everything remains exactly the same while the data is already restored from the snapshots.

$ kubectl create -f px-cassandra-app.yaml
statefulset.apps "cassandra" created

Check the data through the cqlsh from one the Cassandra pods.

$ kubectl exec cassandra-0 -- cqlsh -e 'select * from classicmodels.offices'

 officecode | addressline1           | addressline2 | city          | country   | phone            | postalcode | state      | territory
------------+------------------------+--------------+---------------+-----------+------------------+------------+------------+-----------
          6 |  5-11 Wentworth Avenue |     Floor #2 |        Sydney | Australia |  +61 2 9264 2451 |   NSW 2010 |       null |      APAC
          7 |    25 Old Broad Street |      Level 7 |        London |        UK | +44 20 7877 2041 |   EC2N 1HN |       null |      EMEA
          4 | 43 Rue Jouffroy abbans |         null |         Paris |    France |  +33 14 723 4404 |      75017 |       null |      EMEA
          3 |   523 East 53rd Street |      apt. 5A |           NYC |       USA |  +1 212 555 3000 |      10022 |         NY |        NA
          5 |            4-1 Kioicho |         null |         Tokyo |     Japan |  +81 33 224 5000 |   102-8578 | Chiyoda-Ku |     Japan
          8 |                    BKC |   Building 2 |        Mumbai |        MH |   +91 22 8765434 |     400051 |       null |      APAC
          2 |       1550 Court Place |    Suite 102 |        Boston |       USA |  +1 215 837 0825 |      02107 |         MA |        NA
          1 |      100 Market Street |    Suite 300 | San Francisco |       USA |  +1 650 219 4782 |      94080 |         CA |        NA

(8 rows)

Congratulations! You have successfully restored an application consistent snapshot for Cassandra.
 

Summary

Portworx can be easily deployed on IBM Cloud Kubernetes Service to run stateful workloads in production. Through the integration of STORK, DevOps and StorageOps teams can seamlessly run highly available database clusters in IKS. They can perform traditional operations such as volume expansion, backup, and recovery for the cloud native applications in an automated and efficient manner.

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Contributor | Certified Kubernetes Administrator (CKA) and Developer (CKAD)

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