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.

pkg/lock/lock_test.go

@@ -0,0 +1,192 @@
+/*
+ * Minio Cloud Storage, (C) 2016 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 lock
+
+import (
+	"io/ioutil"
+	"os"
+	"testing"
+	"time"
+)
+
+// Test lock fails.
+func TestLockFail(t *testing.T) {
+	f, err := ioutil.TempFile("", "lock")
+	if err != nil {
+		t.Fatal(err)
+	}
+	f.Close()
+	defer func() {
+		err = os.Remove(f.Name())
+		if err != nil {
+			t.Fatal(err)
+		}
+	}()
+
+	_, err = LockedOpenFile(f.Name(), os.O_APPEND, 0600)
+	if err == nil {
+		t.Fatal("Should fail here")
+	}
+}
+
+// Tests lock directory fail.
+func TestLockDirFail(t *testing.T) {
+	d, err := ioutil.TempDir("", "lockDir")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer func() {
+		err = os.Remove(d)
+		if err != nil {
+			t.Fatal(err)
+		}
+	}()
+
+	_, err = LockedOpenFile(d, os.O_APPEND, 0600)
+	if err == nil {
+		t.Fatal("Should fail here")
+	}
+}
+
+// Tests rwlock methods.
+func TestRWLockedFile(t *testing.T) {
+	f, err := ioutil.TempFile("", "lock")
+	if err != nil {
+		t.Fatal(err)
+	}
+	f.Close()
+	defer func() {
+		err = os.Remove(f.Name())
+		if err != nil {
+			t.Fatal(err)
+		}
+	}()
+
+	rlk, err := RLockedOpenFile(f.Name())
+	if err != nil {
+		t.Fatal(err)
+	}
+	if rlk.Size() != 0 {
+		t.Fatal("File size should be zero", rlk.Size())
+	}
+	isClosed := rlk.IsClosed()
+	if isClosed {
+		t.Fatal("File ref count shouldn't be zero")
+	}
+
+	// Increase reference count to 2.
+	rlk.IncLockRef()
+
+	isClosed = rlk.IsClosed()
+	if isClosed {
+		t.Fatal("File ref count shouldn't be zero")
+	}
+
+	// Decrease reference count by 1.
+	if err = rlk.Close(); err != nil {
+		t.Fatal(err)
+	}
+
+	isClosed = rlk.IsClosed()
+	if isClosed {
+		t.Fatal("File ref count shouldn't be zero")
+	}
+
+	// Decrease reference count by 1.
+	if err = rlk.Close(); err != nil {
+		t.Fatal(err)
+	}
+
+	// Now file should be closed.
+	isClosed = rlk.IsClosed()
+	if !isClosed {
+		t.Fatal("File ref count should be zero")
+	}
+
+	// Closing a file again should result in invalid argument.
+	if err = rlk.Close(); err != os.ErrInvalid {
+		t.Fatal(err)
+	}
+
+	_, err = newRLockedFile(nil)
+	if err != os.ErrInvalid {
+		t.Fatal("Unexpected error", err)
+	}
+}
+
+// Tests lock and unlock semantics.
+func TestLockAndUnlock(t *testing.T) {
+	f, err := ioutil.TempFile("", "lock")
+	if err != nil {
+		t.Fatal(err)
+	}
+	f.Close()
+	defer func() {
+		err = os.Remove(f.Name())
+		if err != nil {
+			t.Fatal(err)
+		}
+	}()
+
+	// lock the file
+	l, err := LockedOpenFile(f.Name(), os.O_WRONLY, 0600)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// unlock the file
+	if err = l.Close(); err != nil {
+		t.Fatal(err)
+	}
+
+	// try lock the unlocked file
+	dupl, err := LockedOpenFile(f.Name(), os.O_WRONLY|os.O_CREATE, 0600)
+	if err != nil {
+		t.Errorf("err = %v, want %v", err, nil)
+	}
+
+	// blocking on locked file
+	locked := make(chan struct{}, 1)
+	go func() {
+		bl, blerr := LockedOpenFile(f.Name(), os.O_WRONLY, 0600)
+		if blerr != nil {
+			t.Fatal(blerr)
+		}
+		locked <- struct{}{}
+		if blerr = bl.Close(); blerr != nil {
+			t.Fatal(blerr)
+		}
+	}()
+
+	select {
+	case <-locked:
+		t.Error("unexpected unblocking")
+	case <-time.After(100 * time.Millisecond):
+	}
+
+	// unlock
+	if err = dupl.Close(); err != nil {
+		t.Fatal(err)
+	}
+
+	// the previously blocked routine should be unblocked
+	select {
+	case <-locked:
+	case <-time.After(1 * time.Second):
+		t.Error("unexpected blocking")
+	}
+}