CockroachDB Helm Chart

Prerequisites Details

• Kubernetes 1.5 (for StatefulSet support)
• PV support on the underlying infrastructure

StatefulSet Details

• http://kubernetes.io/docs/concepts/abstractions/controllers/statefulsets/

StatefulSet Caveats

• http://kubernetes.io/docs/concepts/abstractions/controllers/statefulsets/#limitations

Todo

• Support setting up clusters with certificate-based authentication

Chart Details

This chart will do the following:

• Set up a dynamically scalable CockroachDB cluster using a Kubernetes StatefulSet

Installing the Chart

To install the chart with the release name my-release:

helm repo add incubator http://storage.googleapis.com/kubernetes-charts-incubator
helm install --name my-release incubator/cockroachdb

Configuration

The following tables lists the configurable parameters of the CockroachDB chart and their default values.

Parameter	Description	Default
Name	Chart name	cockroachdb
Image	Container image name	cockroachdb/cockroach
ImageTag	Container image tag	latest
ImagePullPolicy	Container pull policy	Always
Replicas	k8s statefulset replicas	3
MinAvailable	k8s PodDisruptionBudget parameter	67%
Component	k8s selector key	cockroachdb
GrpcPort	CockroachDB primary serving port	26257
HttpPort	CockroachDB HTTP port	8080
Cpu	Container requested cpu	100m
Memory	Container requested memory	512Mi
Storage	Persistent volume size	1Gi
StorageClass	Persistent volume class	anything

Specify each parameter using the --set key=value[,key=value] argument to helm install.

Alternatively, a YAML file that specifies the values for the parameters can be provided while installing the chart. For example,

helm install --name my-release -f values.yaml incubator/cockroachdb

Tip: You can use the default values.yaml

Deep dive

Connecting to the CockroachDB cluster

Once you've created the cluster, you can start talking to it it by connecting to its "public" service. CockroachDB is PostgreSQL wire protocol compatible so there's a wide variety of supported clients. For the sake of example, we'll open up a SQL shell using CockroachDB's built-in shell and play around with it a bit, like this (likely needing to replace "my-release-cockroachdb-public" with the name of the "-public" service that was created with your installed chart):

$ kubectl run -it --rm cockroach-client \
    --image=cockroachdb/cockroach \
    --restart=Never \
    --command -- ./cockroach sql --host my-release-cockroachdb-public
Waiting for pod default/cockroach-client to be running, status is Pending,
pod ready: false
If you don't see a command prompt, try pressing enter.
root@my-release-cockroachdb-public:26257> SHOW DATABASES;
+--------------------+
|      Database      |
+--------------------+
| information_schema |
| pg_catalog         |
| system             |
+--------------------+
(3 rows)
root@my-release-cockroachdb-public:26257> CREATE DATABASE bank;
CREATE DATABASE
root@my-release-cockroachdb-public:26257> CREATE TABLE bank.accounts (id INT
PRIMARY KEY, balance DECIMAL);
CREATE TABLE
root@my-release-cockroachdb-public:26257> INSERT INTO bank.accounts VALUES
(1234, 10000.50);
INSERT 1
root@my-release-cockroachdb-public:26257> SELECT * FROM bank.accounts;
+------+---------+
|  id  | balance |
+------+---------+
| 1234 | 10000.5 |
+------+---------+
(1 row)
root@my-release-cockroachdb-public:26257> \q
Waiting for pod default/cockroach-client to terminate, status is Running
pod "cockroach-client" deleted

Cluster health

Because our pod spec includes regular health checks of the CockroachDB processes, simply running kubectl get pods and looking at the STATUS column is sufficient to determine the health of each instance in the cluster.

If you want more detailed information about the cluster, the best place to look is the admin UI.

Accessing the admin UI

If you want to see information about how the cluster is doing, you can try pulling up the CockroachDB admin UI by port-forwarding from your local machine to one of the pods (replacing "release-cockroachdb-0" with one of your pods' names):

kubectl port-forward release-cockroachdb-0 8080

Once you’ve done that, you should be able to access the admin UI by visiting http://localhost:8080/ in your web browser.

Failover

If any CockroachDB member fails it gets restarted or recreated automatically by the Kubernetes infrastructure, and will rejoin the cluster automatically when it comes back up. You can test this scenario by killing any of the pods:

kubectl delete pod my-release-cockroachdb-1

$ kubectl get pods -l "component=my-release-cockroachdb"
NAME                      READY     STATUS        RESTARTS   AGE
my-release-cockroachdb-0  1/1       Running       0          5m
my-release-cockroachdb-2  1/1       Running       0          5m

After a while:

$ kubectl get pods -l "component=my-release-cockroachdb"
NAME                      READY     STATUS        RESTARTS   AGE
my-release-cockroachdb-0  1/1       Running       0          5m
my-release-cockroachdb-1  1/1       Running       0          20s
my-release-cockroachdb-2  1/1       Running       0          5m

You can check state of re-joining from the new pod's logs:

$ kubectl logs my-release-cockroachdb-1
[...]
I161028 19:32:09.754026 1 server/node.go:586  [n1] node connected via gossip and
verified as part of cluster {"35ecbc27-3f67-4e7d-9b8f-27c31aae17d6"}
[...]
cockroachdb-0.my-release-cockroachdb.default.svc.cluster.local:26257
build:      beta-20161027-55-gd2d3c7f @ 2016/10/28 19:27:25 (go1.7.3)
admin:      http://0.0.0.0:8080
sql:
postgresql://root@my-release-cockroachdb-1.my-release-cockroachdb.default.svc.cluster.local:26257?sslmode=disable
logs:       cockroach-data/logs
store[0]:   path=cockroach-data
status:     restarted pre-existing node
clusterID:  {35ecbc27-3f67-4e7d-9b8f-27c31aae17d6}
nodeID:     2
[...]

Scaling

Scaling should typically be managed via the helm upgrade command, but StatefulSets don't yet work with helm upgrade. In the meantime until helm upgrade works, if you want to change the number of replicas, you can use the kubectl scale as shown below:

kubectl scale statefulset my-release-cockroachdb --replicas=4