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_queries_prefix.go

@@ -0,0 +1,67 @@
+// 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
+
+// PrefixQuery matches documents that have fields containing terms
+// with a specified prefix (not analyzed).
+//
+// For more details, see
+// https://www.elastic.co/guide/en/elasticsearch/reference/current/query-dsl-prefix-query.html
+type PrefixQuery struct {
+	name      string
+	prefix    string
+	boost     *float64
+	rewrite   string
+	queryName string
+}
+
+// NewPrefixQuery creates and initializes a new PrefixQuery.
+func NewPrefixQuery(name string, prefix string) *PrefixQuery {
+	return &PrefixQuery{name: name, prefix: prefix}
+}
+
+// Boost sets the boost for this query.
+func (q *PrefixQuery) Boost(boost float64) *PrefixQuery {
+	q.boost = &boost
+	return q
+}
+
+func (q *PrefixQuery) Rewrite(rewrite string) *PrefixQuery {
+	q.rewrite = rewrite
+	return q
+}
+
+// QueryName sets the query name for the filter that can be used when
+// searching for matched_filters per hit.
+func (q *PrefixQuery) QueryName(queryName string) *PrefixQuery {
+	q.queryName = queryName
+	return q
+}
+
+// Source returns JSON for the query.
+func (q *PrefixQuery) Source() (interface{}, error) {
+	source := make(map[string]interface{})
+	query := make(map[string]interface{})
+	source["prefix"] = query
+
+	if q.boost == nil && q.rewrite == "" && q.queryName == "" {
+		query[q.name] = q.prefix
+	} else {
+		subQuery := make(map[string]interface{})
+		subQuery["prefix"] = q.prefix
+		if q.boost != nil {
+			subQuery["boost"] = *q.boost
+		}
+		if q.rewrite != "" {
+			subQuery["rewrite"] = q.rewrite
+		}
+		if q.queryName != "" {
+			subQuery["_name"] = q.queryName
+		}
+		query[q.name] = subQuery
+	}
+
+	return source, nil
+}