Combine BatchPoints with the same RoutingTag to one message in amqp output

closes #287

CHANGELOG.md

@@ -28,6 +28,7 @@ of metrics collected and from how many plugins.
 - [#280](https://github.com/influxdb/telegraf/issues/280): Use InfluxDB client v2.
 - [#281](https://github.com/influxdb/telegraf/issues/281): Eliminate need to deep copy Batch Points.
 - [#286](https://github.com/influxdb/telegraf/issues/286): bcache plugin, thanks @cornerot!
+- [#287](https://github.com/influxdb/telegraf/issues/287): Batch AMQP output, thanks @ekini!
 
 ### Bugfixes
 - [#228](https://github.com/influxdb/telegraf/pull/228): New version of package will replace old one. Thanks @ekini!

outputs/amqp/README.md

@@ -4,5 +4,6 @@ This plugin writes to a AMQP exchange using tag, defined in configuration file
 as RoutingTag, as a routing key.
 
 If RoutingTag is empty, then empty routing key will be used.
+Metrics are grouped in batches by RoutingTag.
 
 This plugin doesn't bind exchange to a queue, so it should be done by consumer.

outputs/amqp/amqp.go

@@ -1,6 +1,7 @@
 package amqp
 
 import (
+	"bytes"
 	"fmt"
 	"log"
 	"sync"
@@ -88,6 +89,7 @@ func (q *AMQP) Write(points []*client.Point) error {
 	if len(points) == 0 {
 		return nil
 	}
+	var outbuf = make(map[string][][]byte)
 
 	for _, p := range points {
 		// Combine tags from Point and BatchPoints and grab the resulting
@@ -100,7 +102,10 @@ func (q *AMQP) Write(points []*client.Point) error {
 				key = h
 			}
 		}
+		outbuf[key] = append(outbuf[key], []byte(value))
 
+	}
+	for key, buf := range outbuf {
 		err := q.channel.Publish(
 			q.Exchange, // exchange
 			key,        // routing key
@@ -108,7 +113,7 @@ func (q *AMQP) Write(points []*client.Point) error {
 			false,      // immediate
 			amqp.Publishing{
 				ContentType: "text/plain",
-				Body:        []byte(value),
+				Body:        bytes.Join(buf, []byte("\n")),
 			})
 		if err != nil {
 			return fmt.Errorf("FAILED to send amqp message: %s", err)