added simple kv store

pkg/cluster/kv.go

@@ -0,0 +1,55 @@
+package cluster
+
+import (
+	"errors"
+	"sync"
+
+	"github.com/hashicorp/raft"
+)
+
+var ErrNotLeader = errors.New("not leader")
+
+type kv map[string][]byte
+
+type KV struct {
+	mu sync.Mutex
+	m  kv
+	r  *raft.Raft
+}
+
+func (kv *KV) Get(k string) []byte {
+	kv.mu.Lock()
+	defer kv.mu.Unlock()
+	return kv.m[k]
+}
+
+func (kv *KV) Set(k string, v []byte) error {
+	if kv.r.State() != raft.Leader {
+		return ErrNotLeader
+	}
+
+	c := &raftCmd{SET, k, v}
+	b, err := gob.Marshal(c)
+	if err != nil {
+		return err
+	}
+
+	f := kv.r.Apply(b, raftTimeout)
+	return f.Error()
+}
+
+// Delete deletes the given key.
+func (kv *KV) Delete(k string) error {
+	if kv.r.State() != raft.Leader {
+		return ErrNotLeader
+	}
+
+	c := &raftCmd{Op: DELETE, K: k}
+	b, err := gob.Marshal(c)
+	if err != nil {
+		return err
+	}
+
+	f := kv.r.Apply(b, raftTimeout)
+	return f.Error()
+}