From e2743d05e85c48567b4c5b93e2b891243a02e077 Mon Sep 17 00:00:00 2001
From: Krishna Srinivas <krishna@minio.io>
Date: Thu, 16 Jun 2016 08:50:38 +0530
Subject: [PATCH] FS: remove .minio directory if .minio/multipart is empty.
 (#1899)

fixes #1886
---
 fs-v1.go         | 20 ++++++++++++++++++++
 object-common.go | 13 +++++++++++++
 signals.go       | 49 ++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 82 insertions(+)
 create mode 100644 signals.go

diff --git a/fs-v1.go b/fs-v1.go
index eef7f1b54..6841cc6e3 100644
--- a/fs-v1.go
+++ b/fs-v1.go
@@ -49,6 +49,22 @@ func loadFormatFS(storageDisk StorageAPI) ([]byte, error) {
 	return readAll(storageDisk, minioMetaBucket, fsFormatJSONFile)
 }
 
+// Should be called when process shuts down.
+func shutdownFS(storage StorageAPI) {
+	_, err := storage.ListDir(minioMetaBucket, mpartMetaPrefix)
+	if err != errFileNotFound {
+		// Multipart directory is not empty hence do not remove .minio volume.
+		os.Exit(0)
+	}
+	prefix := ""
+	if err := cleanupDir(storage, minioMetaBucket, prefix); err != nil {
+		os.Exit(0)
+		return
+	}
+	storage.DeleteVol(minioMetaBucket)
+	os.Exit(0)
+}
+
 // newFSObjects - initialize new fs object layer.
 func newFSObjects(disk string) (ObjectLayer, error) {
 	storage, err := newStorageAPI(disk)
@@ -72,6 +88,10 @@ func newFSObjects(disk string) (ObjectLayer, error) {
 			return nil, err
 		}
 	}
+	// Register the callback that should be called when the process shuts down.
+	registerShutdown(func() {
+		shutdownFS(storage)
+	})
 	// Return successfully initialized object layer.
 	return fsObjects{
 		storage:            storage,
diff --git a/object-common.go b/object-common.go
index 83b6fa23b..d18e7bb9c 100644
--- a/object-common.go
+++ b/object-common.go
@@ -17,9 +17,11 @@
 package main
 
 import (
+	"os"
 	"path/filepath"
 	"strings"
 	"sync"
+	"syscall"
 )
 
 const (
@@ -27,6 +29,17 @@ const (
 	blockSizeV1 = 10 * 1024 * 1024 // 10MiB.
 )
 
+// Register callback functions that needs to be called when process shutsdown.
+// For now, SIGINT triggers the callbacks, in future controller can trigger
+// shutdown callbacks.
+func registerShutdown(callback func()) {
+	go func() {
+		trapCh := signalTrap(os.Interrupt, syscall.SIGTERM)
+		<-trapCh
+		callback()
+	}()
+}
+
 // House keeping code needed for FS.
 func fsHouseKeeping(storageDisk StorageAPI) error {
 	// Attempt to create `.minio`.
diff --git a/signals.go b/signals.go
new file mode 100644
index 000000000..e7e8b02bf
--- /dev/null
+++ b/signals.go
@@ -0,0 +1,49 @@
+/*
+ * Minio Client, (C) 2015 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 main
+
+import (
+	"os"
+	"os/signal"
+)
+
+// signalTrap traps the registered signals and notifies the caller.
+func signalTrap(sig ...os.Signal) <-chan bool {
+	// channel to notify the caller.
+	trapCh := make(chan bool, 1)
+
+	go func(chan<- bool) {
+		// channel to receive signals.
+		sigCh := make(chan os.Signal, 1)
+		defer close(sigCh)
+
+		// `signal.Notify` registers the given channel to
+		// receive notifications of the specified signals.
+		signal.Notify(sigCh, sig...)
+
+		// Wait for the signal.
+		<-sigCh
+
+		// Once signal has been received stop signal Notify handler.
+		signal.Stop(sigCh)
+
+		// Notify the caller.
+		trapCh <- true
+	}(trapCh)
+
+	return trapCh
+}