Add some blocking so that we don't generate identical UUIDs for API objects.

pkg/util/uuid.go

@@ -0,0 +1,46 @@
+/*
+Copyright 2014 Google Inc. All rights reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package util
+
+import (
+	"sync"
+	"time"
+
+	"code.google.com/p/go-uuid/uuid"
+)
+
+type UUID interface {
+	String() string
+}
+
+var uuidLock sync.Mutex
+
+/**
+ * The UUID package is naive and can generate identical UUIDs if the time interval is quick enough.
+ * Block subsequent UUIDs for 200 Nanoseconds, the UUID uses 100 ns increments, we block for 200 to be safe
+ * Blocks in a go routine, so that the caller doesn't have to wait.
+ * TODO: save old unused UUIDs so that no one has to block.
+ */
+func NewUUID() UUID {
+	uuidLock.Lock()
+	result := uuid.NewUUID()
+	go func() {
+		time.Sleep(200 * time.Nanosecond)
+		uuidLock.Unlock()
+	}()
+	return result
+}