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

vendor/gopkg.in/olivere/elastic.v3/search_aggs_bucket_global.go

@@ -0,0 +1,71 @@
+// Copyright 2012-2015 Oliver Eilhard. All rights reserved.
+// Use of this source code is governed by a MIT-license.
+// See http://olivere.mit-license.org/license.txt for details.
+
+package elastic
+
+// GlobalAggregation defines a single bucket of all the documents within
+// the search execution context. This context is defined by the indices
+// and the document types you’re searching on, but is not influenced
+// by the search query itself.
+// See: http://www.elasticsearch.org/guide/en/elasticsearch/reference/current/search-aggregations-bucket-global-aggregation.html
+type GlobalAggregation struct {
+	subAggregations map[string]Aggregation
+	meta            map[string]interface{}
+}
+
+func NewGlobalAggregation() *GlobalAggregation {
+	return &GlobalAggregation{
+		subAggregations: make(map[string]Aggregation),
+	}
+}
+
+func (a *GlobalAggregation) SubAggregation(name string, subAggregation Aggregation) *GlobalAggregation {
+	a.subAggregations[name] = subAggregation
+	return a
+}
+
+// Meta sets the meta data to be included in the aggregation response.
+func (a *GlobalAggregation) Meta(metaData map[string]interface{}) *GlobalAggregation {
+	a.meta = metaData
+	return a
+}
+
+func (a *GlobalAggregation) Source() (interface{}, error) {
+	// Example:
+	//	{
+	//    "aggs" : {
+	//         "all_products" : {
+	//             "global" : {},
+	//             "aggs" : {
+	//                 "avg_price" : { "avg" : { "field" : "price" } }
+	//             }
+	//         }
+	//    }
+	//	}
+	// This method returns only the { "global" : {} } part.
+
+	source := make(map[string]interface{})
+	opts := make(map[string]interface{})
+	source["global"] = opts
+
+	// AggregationBuilder (SubAggregations)
+	if len(a.subAggregations) > 0 {
+		aggsMap := make(map[string]interface{})
+		source["aggregations"] = aggsMap
+		for name, aggregate := range a.subAggregations {
+			src, err := aggregate.Source()
+			if err != nil {
+				return nil, err
+			}
+			aggsMap[name] = src
+		}
+	}
+
+	// Add Meta data if available
+	if len(a.meta) > 0 {
+		source["meta"] = a.meta
+	}
+
+	return source, nil
+}