add the CompareAndDelete command

store/command_factory.go

@@ -21,6 +21,7 @@ type CommandFactory interface {
 	CreateUpdateCommand(key string, value string, expireTime time.Time) raft.Command
 	CreateDeleteCommand(key string, recursive bool) raft.Command
 	CreateCompareAndSwapCommand(key string, value string, prevValue string, prevIndex uint64, expireTime time.Time) raft.Command
+	CreateCompareAndDeleteCommand(key string, prevValue string, prevIndex uint64) raft.Command
 	CreateSyncCommand(now time.Time) raft.Command
 }
 

store/event.go

@@ -5,14 +5,14 @@ import (
 )
 
 const (
-	Get            = "get"
-	Create         = "create"
-	Set            = "set"
-	Update         = "update"
-	Delete         = "delete"
-	CompareAndSwap = "compareAndSwap"
+	Get              = "get"
+	Create           = "create"
+	Set              = "set"
+	Update           = "update"
+	Delete           = "delete"
+	CompareAndSwap   = "compareAndSwap"
 	CompareAndDelete = "compareAndDelete"
-	Expire         = "expire"
+	Expire           = "expire"
 )
 
 type Event struct {

store/store.go

@@ -50,6 +50,7 @@ type Store interface {
 	CompareAndSwap(nodePath string, prevValue string, prevIndex uint64,
 		value string, expireTime time.Time) (*Event, error)
 	Delete(nodePath string, recursive bool) (*Event, error)
+	CompareAndDelete(nodePath string, prevValue string, prevIndex uint64) (*Event, error)
 	Watch(prefix string, recursive bool, sinceIndex uint64) (<-chan *Event, error)
 	Save() ([]byte, error)
 	Recovery(state []byte) error

store/v2/command_factory.go

@@ -72,6 +72,15 @@ func (f *CommandFactory) CreateCompareAndSwapCommand(key string, value string, p
 	}
 }
 
+// CreateCompareAndDeleteCommand creates a version 2 command to conditionally delete a key from the store.
+func (f *CommandFactory) CreateCompareAndDeleteCommand(key string, prevValue string, prevIndex uint64) raft.Command {
+	return &CompareAndDeleteCommand{
+		Key:       key,
+		PrevValue: prevValue,
+		PrevIndex: prevIndex,
+	}
+}
+
 func (f *CommandFactory) CreateSyncCommand(now time.Time) raft.Command {
 	return &SyncCommand{
 		Time: time.Now(),

store/v2/compare_and_delete_command.go

@@ -0,0 +1,37 @@
+package v2
+
+import (
+	"github.com/coreos/etcd/log"
+	"github.com/coreos/etcd/store"
+	"github.com/coreos/raft"
+)
+
+func init() {
+	raft.RegisterCommand(&CompareAndDeleteCommand{})
+}
+
+// The CompareAndDelete performs a conditional delete on a key in the store.
+type CompareAndDeleteCommand struct {
+	Key       string `json:"key"`
+	PrevValue string `json:"prevValue"`
+	PrevIndex uint64 `json:"prevIndex"`
+}
+
+// The name of the compareAndDelete command in the log
+func (c *CompareAndDeleteCommand) CommandName() string {
+	return "etcd:compareAndDelete"
+}
+
+// Set the key-value pair if the current value of the key equals to the given prevValue
+func (c *CompareAndDeleteCommand) Apply(server raft.Server) (interface{}, error) {
+	s, _ := server.StateMachine().(store.Store)
+
+	e, err := s.CompareAndDelete(c.Key, c.PrevValue, c.PrevIndex)
+
+	if err != nil {
+		log.Debug(err)
+		return nil, err
+	}
+
+	return e, nil
+}