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

bucket-notification-handlers.go

@@ -0,0 +1,211 @@
+/*
+ * 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 main
+
+import (
+	"bytes"
+	"encoding/xml"
+	"io"
+	"net/http"
+	"path"
+
+	"github.com/gorilla/mux"
+)
+
+const (
+	bucketConfigPrefix       = "buckets"
+	bucketNotificationConfig = "notification.xml"
+)
+
+// loads notifcation config if any for a given bucket, returns back structured notification config.
+func (api objectAPIHandlers) loadNotificationConfig(bucket string) (nConfig notificationConfig, err error) {
+	notificationConfigPath := path.Join(bucketConfigPrefix, bucket, bucketNotificationConfig)
+	var objInfo ObjectInfo
+	objInfo, err = api.ObjectAPI.GetObjectInfo(minioMetaBucket, notificationConfigPath)
+	if err != nil {
+		switch err.(type) {
+		case ObjectNotFound:
+			return notificationConfig{}, nil
+		}
+		return notificationConfig{}, err
+	}
+	var buffer bytes.Buffer
+	err = api.ObjectAPI.GetObject(minioMetaBucket, notificationConfigPath, 0, objInfo.Size, &buffer)
+	if err != nil {
+		switch err.(type) {
+		case ObjectNotFound:
+			return notificationConfig{}, nil
+		}
+		return notificationConfig{}, err
+	}
+
+	// Unmarshal notification bytes.
+	notificationConfigBytes := buffer.Bytes()
+	if err = xml.Unmarshal(notificationConfigBytes, &nConfig); err != nil {
+		return notificationConfig{}, err
+	} // Successfully marshalled notification configuration.
+
+	return nConfig, nil
+}
+
+// GetBucketNotificationHandler - This implementation of the GET
+// operation uses the notification subresource to return the
+// notification configuration of a bucket. If notifications are
+// not enabled on the bucket, the operation returns an empty
+// NotificationConfiguration element.
+func (api objectAPIHandlers) GetBucketNotificationHandler(w http.ResponseWriter, r *http.Request) {
+	// Validate request authorization.
+	if s3Error := checkAuth(r); s3Error != ErrNone {
+		writeErrorResponse(w, r, s3Error, r.URL.Path)
+		return
+	}
+	vars := mux.Vars(r)
+	bucket := vars["bucket"]
+	notificationConfigPath := path.Join(bucketConfigPrefix, bucket, bucketNotificationConfig)
+	objInfo, err := api.ObjectAPI.GetObjectInfo(minioMetaBucket, notificationConfigPath)
+	if err != nil {
+		switch err.(type) {
+		case ObjectNotFound:
+			writeSuccessResponse(w, nil)
+			return
+		}
+		errorIf(err, "Unable to read notification configuration.", notificationConfigPath)
+		writeErrorResponse(w, r, toAPIErrorCode(err), r.URL.Path)
+		return
+	}
+
+	// Indicates if any data was written to the http.ResponseWriter
+	dataWritten := false
+
+	// io.Writer type which keeps track if any data was written.
+	writer := funcToWriter(func(p []byte) (int, error) {
+		if !dataWritten {
+			// Set headers on the first write.
+			// Set standard object headers.
+			setObjectHeaders(w, objInfo, nil)
+
+			// Set any additional requested response headers.
+			setGetRespHeaders(w, r.URL.Query())
+
+			dataWritten = true
+		}
+		return w.Write(p)
+	})
+
+	// Reads the object at startOffset and writes to func writer..
+	err = api.ObjectAPI.GetObject(minioMetaBucket, notificationConfigPath, 0, objInfo.Size, writer)
+	if err != nil {
+		if !dataWritten {
+			switch err.(type) {
+			case ObjectNotFound:
+				writeSuccessResponse(w, nil)
+				return
+			}
+			// Error response only if no data has been written to client yet. i.e if
+			// partial data has already been written before an error
+			// occurred then no point in setting StatusCode and
+			// sending error XML.
+			apiErr := toAPIErrorCode(err)
+			writeErrorResponse(w, r, apiErr, r.URL.Path)
+		}
+		errorIf(err, "Unable to write to client.")
+		return
+	}
+	if !dataWritten {
+		// If ObjectAPI.GetObject did not return error and no data has
+		// been written it would mean that it is a 0-byte object.
+		// call wrter.Write(nil) to set appropriate headers.
+		writer.Write(nil)
+	}
+
+}
+
+// PutBucketNotificationHandler - Minio notification feature enables
+// you to receive notifications when certain events happen in your bucket.
+// Using this API, you can replace an existing notification configuration.
+// The configuration is an XML file that defines the event types that you
+// want Minio to publish and the destination where you want Minio to publish
+// an event notification when it detects an event of the specified type.
+// By default, your bucket has no event notifications configured. That is,
+// the notification configuration will be an empty NotificationConfiguration.
+func (api objectAPIHandlers) PutBucketNotificationHandler(w http.ResponseWriter, r *http.Request) {
+	// Validate request authorization.
+	if s3Error := checkAuth(r); s3Error != ErrNone {
+		writeErrorResponse(w, r, s3Error, r.URL.Path)
+		return
+	}
+	vars := mux.Vars(r)
+	bucket := vars["bucket"]
+
+	_, err := api.ObjectAPI.GetBucketInfo(bucket)
+	if err != nil {
+		errorIf(err, "Unable to bucket info.")
+		writeErrorResponse(w, r, toAPIErrorCode(err), r.URL.Path)
+		return
+	}
+
+	// If Content-Length is unknown or zero, deny the request. PutBucketNotification
+	// always needs a Content-Length if incoming request is not chunked.
+	if !contains(r.TransferEncoding, "chunked") {
+		if r.ContentLength == -1 {
+			writeErrorResponse(w, r, ErrMissingContentLength, r.URL.Path)
+			return
+		}
+	}
+
+	// Reads the incoming notification configuration.
+	var buffer bytes.Buffer
+	if r.ContentLength >= 0 {
+		_, err = io.CopyN(&buffer, r.Body, r.ContentLength)
+	} else {
+		_, err = io.Copy(&buffer, r.Body)
+	}
+	if err != nil {
+		errorIf(err, "Unable to read incoming body.")
+		writeErrorResponse(w, r, toAPIErrorCode(err), r.URL.Path)
+		return
+	}
+
+	var notificationCfg notificationConfig
+	// Unmarshal notification bytes.
+	notificationConfigBytes := buffer.Bytes()
+	if err = xml.Unmarshal(notificationConfigBytes, &notificationCfg); err != nil {
+		errorIf(err, "Unable to parse notification configuration XML.")
+		writeErrorResponse(w, r, ErrMalformedXML, r.URL.Path)
+		return
+	} // Successfully marshalled notification configuration.
+
+	// Validate unmarshalled bucket notification configuration.
+	if s3Error := validateNotificationConfig(notificationCfg); s3Error != ErrNone {
+		writeErrorResponse(w, r, s3Error, r.URL.Path)
+		return
+	}
+
+	// Proceed to save notification configuration.
+	size := int64(len(notificationConfigBytes))
+	data := bytes.NewReader(notificationConfigBytes)
+	notificationConfigPath := path.Join(bucketConfigPrefix, bucket, bucketNotificationConfig)
+	_, err = api.ObjectAPI.PutObject(minioMetaBucket, notificationConfigPath, size, data, nil)
+	if err != nil {
+		errorIf(err, "Unable to write bucket notification configuration.", notificationConfigPath)
+		writeErrorResponse(w, r, toAPIErrorCode(err), r.URL.Path)
+		return
+	}
+
+	// Success.
+	writeSuccessResponse(w, nil)
+}