fix update PUT handler

store/compare_and_swap_command.go

@@ -0,0 +1,41 @@
+package store
+
+import (
+	"time"
+
+	"github.com/coreos/etcd/log"
+	"github.com/coreos/go-raft"
+)
+
+func init() {
+	raft.RegisterCommand(&CompareAndSwapCommand{})
+}
+
+// The CompareAndSwap performs a conditional update on a key in the store.
+type CompareAndSwapCommand struct {
+	Key        string    `json:"key"`
+	Value      string    `json:"value"`
+	ExpireTime time.Time `json:"expireTime"`
+	PrevValue  string    `json: prevValue`
+	PrevIndex  uint64    `json: prevIndex`
+}
+
+// The name of the testAndSet command in the log
+func (c *CompareAndSwapCommand) CommandName() string {
+	return "etcd:compareAndSwap"
+}
+
+// Set the key-value pair if the current value of the key equals to the given prevValue
+func (c *CompareAndSwapCommand) Apply(server raft.Server) (interface{}, error) {
+	s, _ := server.StateMachine().(Store)
+
+	e, err := s.CompareAndSwap(c.Key, c.PrevValue, c.PrevIndex,
+		c.Value, c.ExpireTime, server.CommitIndex(), server.Term())
+
+	if err != nil {
+		log.Debug(err)
+		return nil, err
+	}
+
+	return e, nil
+}