api: Implement bucket notification. (#2271)

* Implement basic S3 notifications through queues

Supports multiple queues and three basic queue types:

1. NilQueue -- messages don't get sent anywhere
2. LogQueue -- messages get logged
3. AmqpQueue -- messages are sent to an AMQP queue

* api: Implement bucket notification.

Supports two different queue types

- AMQP
- ElasticSearch.

* Add support for redis

fs-v1.go

@@ -64,17 +64,29 @@ func loadFormatFS(storageDisk StorageAPI) (format formatConfigV1, err error) {
 
 // Should be called when process shuts down.
 func shutdownFS(storage StorageAPI) {
+	// List if there are any multipart entries.
 	_, err := storage.ListDir(minioMetaBucket, mpartMetaPrefix)
 	if err != errFileNotFound {
-		// Multipart directory is not empty hence do not remove .minio volume.
+		// Multipart directory is not empty hence do not remove '.minio.sys' volume.
 		os.Exit(0)
 	}
+	// List if there are any bucket configuration entries.
+	_, err = storage.ListDir(minioMetaBucket, bucketConfigPrefix)
+	if err != errFileNotFound {
+		// Bucket config directory is not empty hence do not remove '.minio.sys' volume.
+		os.Exit(0)
+	}
+	// Cleanup everything else.
 	prefix := ""
-	if err := cleanupDir(storage, minioMetaBucket, prefix); err != nil {
-		os.Exit(0)
-		return
+	if err = cleanupDir(storage, minioMetaBucket, prefix); err != nil {
+		errorIf(err, "Unable to cleanup minio meta bucket")
+		os.Exit(1)
 	}
-	storage.DeleteVol(minioMetaBucket)
+	if err = storage.DeleteVol(minioMetaBucket); err != nil {
+		errorIf(err, "Unable to delete minio meta bucket", minioMetaBucket)
+		os.Exit(1)
+	}
+	// Successful exit.
 	os.Exit(0)
 }
 
@@ -184,6 +196,10 @@ func (fs fsObjects) ListBuckets() ([]BucketInfo, error) {
 		if !IsValidBucketName(vol.Name) {
 			continue
 		}
+		// Ignore the volume special bucket.
+		if vol.Name == minioMetaBucket {
+			continue
+		}
 		bucketInfos = append(bucketInfos, BucketInfo{
 			Name:    vol.Name,
 			Created: vol.Created,