etcd-rover

etcd-rover is a 2 node etcd cluster helper base drbd and keepalived, which makes etcd becomes available in edge scenarios where hardware resources are scarce.

Architect

How etcd-rover work

1. etcd2 and etcd2's should be run by etcd-rover. etcd-rover will start keepalived and drbd once you start etcd-rover container in each node
2. drbd immediately establishes the connection between disk2 and disk3
3. keepalived starts preempting for master, if node1 becomes master, etcd-rover will set drbd with disk2 primary and then start etcd2 process.
4. if node1 down, node2 become master, etcd-rover will set disk3 primary and then start etcd2's in node 2

notes: drbd synchronous replication protocol. Local write operations on the primary node are considered completed only after both the local and the remote disk write(s) have been confirmed.

Components Operation

Container Image

• alaudapublic/etcd-rover
• alaudapublic/etcd-rover-config
• alaudapublic/drbd-load

build image

docker build -t etcd-rover-config:latest -f ./load-config.Dockerfile
docker build -t etcd-rover:latest -f ./Dockerfile

kubernetes static pod yaml

file exists in manifest/rover.yaml
User should provide two node's disk,ip,gateway,host name, and vip of keepalived.

Dependencies

• drbd9 kernel module

There are 2 ways install drbd

1. manifest/rover.yaml has an init container which can auto build drbd kernel module and load.
2. User manual installation

Limitations

if node1 and node2 rolling restart in a short period of time. drbd replicate data operation not be completed in such period of time. etcd will lose data in such scenario.