Orchestration

Other tutorials in this section feature the ways that CockroachDB automates operations for you. On top of this built-in automation, you can use a third-party orchestration system to simplify and automate even more of your operations, from deployment to scaling to overall cluster management.

This page walks you through a simple demonstration, using the open-source Kubernetes orchestration system. Starting with a few configuration files, you'll quickly create an insecure 3-node local cluster. You'll run a load generator against the cluster and then simulate node failure, watching how Kubernetes auto-restarts without the need for any manual intervention. You'll then scale the cluster with a single command before shutting the cluster down, again with a single command.

Before You Begin

Before getting started, it's helpful to review some Kubernetes-specific terminology:

Feature	Description
minikube	This is the tool you'll use to run a Kubernetes cluster inside a VM on your local workstation.
pod	A pod is a group of one of more Docker containers. In this tutorial, all pods will run on your local workstation, each containing one Docker container running a single CockroachDB node. You'll start with 3 pods and grow to 4.
StatefulSet	A StatefulSet is a group of pods treated as stateful units, where each pod has distinguishable network identity and always binds back to the same persistent storage on restart. StatefulSets are considered stable as of Kubernetes version 1.9 after reaching beta in version 1.5.
persistent volume	A persistent volume is a piece of local storage mounted into a pod. The lifetime of a persistent volume is decoupled from the lifetime of the pod that's using it, ensuring that each CockroachDB node binds back to the same storage on restart. When using minikube, persistent volumes are external temporary directories that endure until they are manually deleted or until the entire Kubernetes cluster is deleted.
persistent volume claim	When pods are created (one per CockroachDB node), each pod will request a persistent volume claim to “claim” durable storage for its node.

Step 1. Start Kubernetes

1. Follow Kubernetes' documentation to install minikube, the tool used to run Kubernetes locally, for your OS. This includes installing a hypervisor and kubectl, the command-line tool used to managed Kubernetes from your local workstation.

   Note:

   Make sure you install minikube version 0.21.0 or later. Earlier versions do not include a Kubernetes server that supports the maxUnavailability field and PodDisruptionBudget resource type used in the CockroachDB StatefulSet configuration.

2. Start a local Kubernetes cluster:

   $ minikube start
   

Step 2. Start CockroachDB nodes

When starting a cluster manually, you run the cockroach start command multiple times, once per node. In this step, you use a Kubernetes StatefulSet configuration instead, reducing the effort of starting 3 nodes to a single command.

1. From your local workstation, use our cockroachdb-statefulset.yaml file to create the StatefulSet that automatically creates 3 pods, each with a CockroachDB node running inside it:

   $ kubectl create -f https://raw.githubusercontent.com/cockroachdb/cockroach/master/cloud/kubernetes/cockroachdb-statefulset.yaml
   

   service "cockroachdb-public" created
   service "cockroachdb" created
   poddisruptionbudget "cockroachdb-budget" created
   statefulset "cockroachdb" created
   

   Alternatively, if you'd rather start with a configuration file that has been customized for performance:

   1. Download our performance version of cockroachdb-statefulset-insecure.yaml:

      $ curl -O https://raw.githubusercontent.com/cockroachdb/cockroach/master/cloud/kubernetes/performance/cockroachdb-statefulset-insecure.yaml
      

   2. Modify the file wherever there is a TODO comment.

   3. Use the file to create the StatefulSet and start the cluster:

      $ kubectl create -f cockroachdb-statefulset-insecure.yaml
      

2. Confirm that three pods are Running successfully. Note that they will not be considered Ready until after the cluster has been initialized:

   $ kubectl get pods
   

   NAME            READY     STATUS    RESTARTS   AGE
   cockroachdb-0   0/1       Running   0          2m
   cockroachdb-1   0/1       Running   0          2m
   cockroachdb-2   0/1       Running   0          2m
   

3. Confirm that the persistent volumes and corresponding claims were created successfully for all three pods:

   $ kubectl get persistentvolumes
   

   NAME                                       CAPACITY   ACCESSMODES   RECLAIMPOLICY   STATUS    CLAIM                           REASON    AGE
   pvc-52f51ecf-8bd5-11e6-a4f4-42010a800002   1Gi        RWO           Delete          Bound     default/datadir-cockroachdb-0             26s
   pvc-52fd3a39-8bd5-11e6-a4f4-42010a800002   1Gi        RWO           Delete          Bound     default/datadir-cockroachdb-1             27s
   pvc-5315efda-8bd5-11e6-a4f4-42010a800002   1Gi        RWO           Delete          Bound     default/datadir-cockroachdb-2             27s
   

Step 3. Initialize the cluster

1. Use our cluster-init.yaml file to perform a one-time initialization that joins the nodes into a single cluster:

   $ kubectl create -f https://raw.githubusercontent.com/cockroachdb/cockroach/master/cloud/kubernetes/cluster-init.yaml
   

   job "cluster-init" created
   

2. Confirm that cluster initialization has completed successfully. The job should be considered successful and the CockroachDB pods should soon be considered Ready:

   $ kubectl get job cluster-init
   

   NAME           DESIRED   SUCCESSFUL   AGE
   cluster-init   1         1            2m
   

   $ kubectl get pods
   

   NAME            READY     STATUS    RESTARTS   AGE
   cockroachdb-0   1/1       Running   0          3m
   cockroachdb-1   1/1       Running   0          3m
   cockroachdb-2   1/1       Running   0          3m
   

Step 4. Test the cluster

To test the cluster, launch a temporary pod for using the built-in SQL client, and then use a deployment configuration file to run a high-traffic load generator against the cluster from another pod.

1. Launch a temporary interactive pod and start the built-in SQL client inside it:

   $ kubectl run cockroachdb -it --image=cockroachdb/cockroach --rm --restart=Never \
   -- sql --insecure --host=cockroachdb-public
   

2. Run some basic CockroachDB SQL statements:

   > CREATE DATABASE bank;
   

   > CREATE TABLE bank.accounts (id INT PRIMARY KEY, balance DECIMAL);
   

   > INSERT INTO bank.accounts VALUES (1, 1000.50);
   

   > SELECT * FROM bank.accounts;
   

   +----+---------+
   | id | balance |
   +----+---------+
   |  1 |  1000.5 |
   +----+---------+
   (1 row)
   

3. Exit the SQL shell and delete the temporary pod:

   > \q
   

4. Use our example-app.yaml file to launch a pod and run a load generator against the cluster from the pod:

   $ kubectl create -f https://raw.githubusercontent.com/cockroachdb/cockroach/master/cloud/kubernetes/example-app.yaml
   

   deployment "example" created
   

5. Verify that the pod for the load generator was added successfully:

   $ kubectl get pods
   

   NAME                      READY     STATUS    RESTARTS   AGE
   cockroachdb-0             1/1       Running   0          28m
   cockroachdb-1             1/1       Running   0          27m
   cockroachdb-2             1/1       Running   0          10m
   example-545f866f5-2gsrs   1/1       Running   0          25m
   

Step 5. Monitor the cluster

To access the Admin UI and monitor the cluster's state and the load generator's activity:

1. Port-forward from your local machine to one of the pods:

   $ kubectl port-forward cockroachdb-0 8080
   

   Forwarding from 127.0.0.1:8080 -> 8080
   

2. Go to http://localhost:8080 and click Metrics on the left-hand navigation bar.

3. On the Overview dashboard, note that there are 3 healthy nodes with many SQL inserts executing per second across them.

   

4. Click the Databases tab on the left to verify that the bank database you created manually, as well as the kv database created by the load generated, are listed.

Step 6. Simulate node failure

Based on the replicas: 3 line in the StatefulSet configuration, Kubernetes ensures that three pods/nodes are running at all times. When a pod/node fails, Kubernetes automatically creates another pod/node with the same network identity and persistent storage.

To see this in action:

1. Terminate one of the CockroachDB nodes:

   $ kubectl delete pod cockroachdb-2
   

   pod "cockroachdb-2" deleted
   

2. In the Admin UI, the Summary panel will soon show one node as Suspect. As Kubernetes auto-restarts the node, watch how the node once again becomes healthy.

3. Back in the terminal, verify that the pod was automatically restarted:

   $ kubectl get pod cockroachdb-2
   

   NAME            READY     STATUS    RESTARTS   AGE
   cockroachdb-2   1/1       Running   0          12s
   

Step 7. Scale the cluster

1. Use the kubectl scale command to add a pod for another CockroachDB node:

   $ kubectl scale statefulset cockroachdb --replicas=4
   

   statefulset "cockroachdb" scaled
   

2. Verify that the pod for a fourth node, cockroachdb-3, was added successfully:

   $ kubectl get pods
   

   NAME                      READY     STATUS    RESTARTS   AGE
   cockroachdb-0             1/1       Running   0          28m
   cockroachdb-1             1/1       Running   0          27m
   cockroachdb-2             1/1       Running   0          10m
   cockroachdb-3             1/1       Running   0          5s
   example-545f866f5-2gsrs   1/1       Running   0          25m
   

Step 8. Stop the cluster

• If you plan to restart the cluster, use the minikube stop command. This shuts down the minikube virtual machine but preserves all the resources you created:

  $ minikube stop
  

  Stopping local Kubernetes cluster...
  Machine stopped.
  

  You can restore the cluster to its previous state with minikube start.

• If you do not plan to restart the cluster, use the minikube delete command. This shuts down and deletes the minikube virtual machine and all the resources you created, including persistent volumes:

  $ minikube delete
  

  Deleting local Kubernetes cluster...
  Machine deleted.
  

  Tip:

  To retain logs, copy them from each pod's stderr before deleting the cluster and all its resources. To access a pod's standard error stream, run kubectl logs <podname>.

See Also

Use a local cluster to explore these other core CockroachDB features:

• Data Replication
• Fault Tolerance & Recovery
• Automatic Rebalancing
• Cross-Cloud Migration
• Follow-the-Workload
• JSON Support

You might also want to learn how to orchestrate a production deployment of CockroachDB with Kubernetes.