ktsakalozos / k8s-dqlite

Dqlite for Kubernetes

Dqlite for Kubernetes

This project is a drop in replacement for etcd on Kubernetes.

If you are looking for an in-memory database to replace etcd in your K8s cluster dqlite might be just right for you. Here is what you are getting:

• distributed sqlite
• in-memory
• high availability
• almost zero ops

Building

To build the project you need to build:

• raft: follow the instructions in https://github.com/canonical/raft
• sqlite: libsqlite-dev should be enough or you could build sqlite from https://github.com/sqlite/sqlite
• dqlite: follow the instructions at https://github.com/canonical/dqlite

Finally, you can build this project with:

export CGO_LDFLAGS_ALLOW="-Wl,-z,now"
go build -o k8s-dqlite -tags libsqlite3,dqlite k8s-dqlite.go

As getting the above dependencies right may be a challenge we have packaged everything in a snap. You can look into snap/snapcraft.yaml on how each dependency is build or just build the snap with:

snapcraft

Installing

Prepare a directory containing:

• init.yaml with Address: <host_IP>:<port_used_by_dqlite>
• cluster.crt and cluster.key pair.

Here is a script to build you can use:

mkdir -p /var/data/
IP="127.0.0.1"
PORT="29001"
DNS=$(/bin/hostname)

echo "Address: $IP:$PORT" > /var/data/init.yaml
mkdir -p /var/tmp/

# Find the csr-dqlite.conf.template in the project
cp /config/csr-dqlite.conf.template /var/tmp/csr-dqlite.conf
sed -i 's/HOSTNAME/'"${DNS}"'/g' /var/tmp/csr-dqlite.conf
sed -i 's/HOSTIP/'"${IP}"'/g' /var/tmp/csr-dqlite.conf
openssl req -x509 -newkey rsa:4096 -sha256 -days 3650 -nodes -keyout /var/data/cluster.key -out ${SNAP_DATA}/var/data/cluster.crt -subj "/CN=k8s" -config /var/tmp/csr-dqlite.conf -extensions v3_ext
chmod -R o-rwX /var/data

You are now ready to start k8s-dqlite with:

k8s-dqlite --storage-dir=/var/data/

The --listen option allows you to set the endpoint where dqlite should listen to for connections from kubernetes API server. By default k8s-dqlite will be listening for connections at tcp://127.0.0.1:12379.

The snap package takes care of this installation step so you may want to use the snap you build above:

sudo snap install ./k8s-dqlite_latest_amd64.snap --classic --dangerous

Configuring the API server

To point the API server to k8s-dqlite use the following arguments:

# Endpoint k8s-dqlite listens at
--etcd-servers="http://<IP>:<PORT>"
# By default --etcd-servers="http://127.0.0.1:12379"

# Point to the cluster key pair
--etcd-certfile=/data/cluster.crt
--etcd-keyfile=/var/data/cluster.key

# If you are using the snap comment in these lines
#--etcd-certfile=/var/snap/k8s-dqlite/current/var/data/cluster.crt
#--etcd-keyfile=/var/snap/k8s-dqlite/current/var/data/cluster.key

Highly Available Dqlite

The following steps allows one to setup a highly available dqlite backend.

In the example below, we will setup a 3 node HA dqlite.

Steps:

1. On the main node, make sure that this node is listening to the default network interface.
2. On the joining node and after installing k8s-dqlite, you need to backup the dqlite data directory for example (/var/data).
3. Delete the dqlite data directory.
4. Copy the cluster.crt and cluster.key from the main node and place it into the joining node's /var/data.
5. Create the init.yaml file with the following content

Cluster:
- <the ip of the main node>:29001
Address: <ip of the joining node>:29001

6. Start k8s-dqlite process

k8s-dqlite --storage-dir=/var/data/

7. Go to the main node and verify that the joining node is visible from the dqlite cluster.

dqlite -s file:///var/data/cluster.yaml -c /var/data/cluster.crt -k /var/data/cluster.key -f json k8s .cluster

8. Repeat from step #2 to join another node.