cluster: add etcd based leader elector and factory

cluster/etcd_elector_factory.go

@@ -0,0 +1,46 @@
+// +build kvdb_etcd
+
+package cluster
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/lightningnetwork/lnd/channeldb/kvdb/etcd"
+)
+
+// makeEtcdElector will construct a new etcdLeaderElector. It expects a cancel
+// context a unique (in the cluster) LND id and a *etcd.Config as arguments.
+func makeEtcdElector(ctx context.Context, args ...interface{}) (LeaderElector,
+	error) {
+
+	if len(args) != 3 {
+		return nil, fmt.Errorf("invalid number of arguments to "+
+			"cluster.makeEtcdElector(): expected 3, got %v",
+			len(args))
+	}
+
+	id, ok := args[0].(string)
+	if !ok {
+		return nil, fmt.Errorf("invalid argument (0) to " +
+			"cluster.makeEtcdElector(), expected: string")
+	}
+
+	electionPrefix, ok := args[1].(string)
+	if !ok {
+		return nil, fmt.Errorf("invalid argument (1) to " +
+			"cluster.makeEtcdElector(), expected: string")
+	}
+
+	etcdCfg, ok := args[2].(*etcd.Config)
+	if !ok {
+		return nil, fmt.Errorf("invalid argument (2) to " +
+			"cluster.makeEtcdElector(), expected: *etcd.Config")
+	}
+
+	return newEtcdLeaderElector(ctx, id, electionPrefix, etcdCfg)
+}
+
+func init() {
+	RegisterLeaderElectorFactory(EtcdLeaderElector, makeEtcdElector)
+}