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This is an archived version of the documentation. View the latest version here.

RethinkDB Cluster on Kubernetes

Setting up a rethinkdb cluster on kubernetes

Features

  • Auto configuration cluster by querying info from k8s
  • Simple

Quick start

Step 1

Rethinkdb will discover peer using endpoints provided by kubernetes service, so first create a service so the following pod can query its endpoint

$kubectl create -f examples/rethinkdb/driver-service.yaml

check out:

$kubectl get services
NAME               LABELS        SELECTOR       IP(S)         PORT(S)
[...]
rethinkdb-driver   db=influxdb   db=rethinkdb   10.0.27.114   28015/TCP

Step 2

start fist server in cluster

$kubectl create -f examples/rethinkdb/rc.yaml

Actually, you can start servers as many as you want at one time, just modify the replicas in rc.ymal

check out again:

$kubectl get pods
NAME                                                  READY     REASON    RESTARTS   AGE
[...]
rethinkdb-rc-r4tb0                                    1/1       Running   0          1m

Done!

Scale

You can scale up you cluster using kubectl scale, and new pod will join to exsits cluster automatically, for example

$kubectl scale rc rethinkdb-rc --replicas=3
scaled

$kubectl get pods
NAME                                                  READY     REASON    RESTARTS   AGE
[...]
rethinkdb-rc-f32c5                                    1/1       Running   0          1m
rethinkdb-rc-m4d50                                    1/1       Running   0          1m
rethinkdb-rc-r4tb0                                    1/1       Running   0          3m

Admin

You need a separate pod (labeled as role:admin) to access Web Admin UI

kubectl create -f examples/rethinkdb/admin-pod.yaml
kubectl create -f examples/rethinkdb/admin-service.yaml

find the service

$kubectl get se
NAME               LABELS        SELECTOR                  IP(S)            PORT(S)
[...]
rethinkdb-admin    db=influxdb   db=rethinkdb,role=admin   10.0.131.19      8080/TCP
                                                           104.197.19.120
rethinkdb-driver   db=influxdb   db=rethinkdb              10.0.27.114      28015/TCP

We request for an external load balancer in the admin-service.yaml file:

type: LoadBalancer

The external load balancer allows us to access the service from outside via an external IP, which is 104.197.19.120 in this case.

Note that you may need to create a firewall rule to allow the traffic, assuming you are using Google Compute Engine:

$ gcloud compute firewall-rules create rethinkdb --allow=tcp:8080

Now you can open a web browser and access to http://104.197.19.120:8080 to manage your cluster.

Why not just using pods in replicas?

This is because kube-proxy will act as a load balancer and send your traffic to different server, since the ui is not stateless when playing with Web Admin UI will cause Connection not open on server error.

BTW

  • gen_pod.sh is using to generate pod templates for my local cluster, the generated pods which is using nodeSelector to force k8s to schedule containers to my designate nodes, for I need to access persistent data on my host dirs. Note that one needs to label the node before 'nodeSelector' can work, see this tutorial

  • see antmanler/rethinkdb-k8s for detail

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