Enable Leader Election

This guide will show you how to enable leader election for your application.

0. Enable leader election in manifest

.nais/app.yaml

spec:
  leaderElection: true

1. Using leader election in your application

javacURL

// Implementation of getJSONFromUrl is left as an exercise for the reader
class Leader {
    public static boolean isLeader() {
        String electorPath = System.getenv("ELECTOR_PATH");
        JSONObject leaderJson = getJSONFromUrl(electorPath);
        String leader = leaderJson.getString("name");
        String hostname = InetAddress.getLocalHost().getHostname();

        return hostname.equals(leader);
    }
}

$ kubectl exec -it elector-sidecar-755b7c5795-7k2qn -c debug bash
root@elector-sidecar-755b7c5795-7k2qn:/# curl $ELECTOR_PATH
{"name":"elector-sidecar-755b7c5795-2kcm7","last_update":"2022-10-18T10:59:58Z"}