2.9 KiB
Running rqlite on Kubernetes
This document provides an example of how to run rqlite as a Kubernetes StatefulSet. The source for the configuration below is available in the Kubernetes Configuration repo.
Creating a cluster
Create Services
The first thing to do is to create two Kubernetes Services. The first service, rqlite-svc-internal, is Headless and allows the nodes to find each other and cluster automatically. It shouldn't be used by rqlite clients. It is the second service, rqlite-svc, that is for clients to talk to the cluster -- this service will get a Cluster IP address which those clients can connect to.
A key difference between rqlite-svc-internal and rqlite-svc is that the second will only contain Pods that are ready to serve traffic. This makes it most suitable for use by end-users of rqlite.
curl -s https://raw.githubusercontent.com/rqlite/kubernetes-configuration/master/service.yaml -o rqlite-service.yaml
kubectl apply -f rqlite-service.yaml
Create a StatefulSet
For a rqlite cluster to function properly in a production environment, the rqlite nodes require a persistent network identifier and storage. This is what a StatefulSet can provide. Retrieve the Stateful set configuration, apply it, and a 3-node rqlite cluster will be created.
curl -s https://raw.githubusercontent.com/rqlite/kubernetes-configuration/master/statefulset-3-node.yaml -o rqlite-3-nodes.yaml
kubectl apply -f rqlite-3-nodes.yaml
Note the args passed to rqlite in the YAML file. The arguments tell rqlite to use dns discovery mode, and to resolve the DNS name rqlite-svc-internal to find the IP addresses of other nodes in the cluster. Furthermore it tells rqlite to wait until three nodes are available (counting itself as one of those nodes) before attempting to form a cluster.
Scaling the cluster
You can grow the cluster at anytime, simply by setting the replica count to the desired cluster size. Shrinking the cluster, however, will require some manual intervention. As well reducing replicas, you will also need to explicitly remove the deprovisioned nodes, or the Leader will continually attempt to contact those nodes.
⚠️ Be careful that you don't reduce the replica count such that there is no longer a quorum of nodes available. If you do this you will render your cluster unusable, and need to perform a manual recovery. The manual recovery process is fully documented.