Implement list, clear locks REST API w/ pkg/madmin support (#3491)

* Filter lock info based on bucket, prefix and time since lock was held
* Implement list and clear locks REST API
* madmin: Add list and clear locks API
* locks: Clear locks matching bucket, prefix, relTime.
* Gather lock information across nodes for both list and clear locks admin REST API.
* docs: Add lock API to management APIs

pkg/madmin/lock-commands_test.go

@@ -0,0 +1,61 @@
+/*
+ * 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 madmin
+
+import (
+	"bytes"
+	"encoding/json"
+	"reflect"
+	"testing"
+)
+
+// Test for getLockInfos helper function.
+func TestGetLockInfos(t *testing.T) {
+	testCases := []struct {
+		// Used to construct a io.Reader holding xml serialized lock information
+		inputLocks []VolumeLockInfo
+	}{
+		// To build a reader with _no_ lock information.
+		{
+			inputLocks: []VolumeLockInfo{},
+		},
+		// To build a reader with _one_ lock information.
+		{
+			inputLocks: []VolumeLockInfo{{Bucket: "bucket", Object: "object"}},
+		},
+	}
+	for i, test := range testCases {
+		jsonBytes, err := json.Marshal(test.inputLocks)
+		if err != nil {
+			t.Fatalf("Test %d - Failed to marshal input lockInfos - %v", i+1, err)
+		}
+		actualLocks, err := getLockInfos(bytes.NewReader(jsonBytes))
+		if err != nil {
+			t.Fatalf("Test %d - Failed to get lock information - %v", i+1, err)
+		}
+		if !reflect.DeepEqual(actualLocks, test.inputLocks) {
+			t.Errorf("Test %d - Expected %v but received %v", i+1, test.inputLocks, actualLocks)
+		}
+	}
+
+	// Invalid json representation of []VolumeLockInfo
+	_, err := getLockInfos(bytes.NewReader([]byte("invalidBytes")))
+	if err == nil {
+		t.Errorf("Test expected to fail, but passed")
+	}
+}