fs: Re-implement object layer to remember the fd (#3509)

This patch re-writes FS backend to support shared backend sharing locks for safe concurrent access across multiple servers.

cmd/lock-rpc-client_test.go

@@ -0,0 +1,68 @@
+/*
+ * Minio Cloud Storage, (C) 2017 Minio, Inc.
+ *
+ * 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 cmd
+
+import (
+	"fmt"
+	"testing"
+	"time"
+
+	"github.com/minio/dsync"
+)
+
+// Tests lock rpc client.
+func TestLockRPCClient(t *testing.T) {
+	lkClient := newLockRPCClient(authConfig{
+		accessKey:       "abcd",
+		secretKey:       "abcd123",
+		serverAddr:      fmt.Sprintf("%X", time.Now().UTC().UnixNano()),
+		serviceEndpoint: pathJoin(lockRPCPath, "/test/1"),
+		secureConn:      false,
+		serviceName:     "Dsync",
+	})
+
+	// Attempt all calls.
+	_, err := lkClient.RLock(dsync.LockArgs{})
+	if err == nil {
+		t.Fatal("Expected for Rlock to fail")
+	}
+
+	_, err = lkClient.Lock(dsync.LockArgs{})
+	if err == nil {
+		t.Fatal("Expected for Lock to fail")
+	}
+
+	_, err = lkClient.RUnlock(dsync.LockArgs{})
+	if err == nil {
+		t.Fatal("Expected for RUnlock to fail")
+	}
+
+	_, err = lkClient.Unlock(dsync.LockArgs{})
+	if err == nil {
+		t.Fatal("Expected for Unlock to fail")
+	}
+
+	_, err = lkClient.ForceUnlock(dsync.LockArgs{})
+	if err == nil {
+		t.Fatal("Expected for ForceUnlock to fail")
+	}
+
+	_, err = lkClient.Expired(dsync.LockArgs{})
+	if err == nil {
+		t.Fatal("Expected for Expired to fail")
+	}
+}