[amqp output] Add ability to specify influxdb database

and retention policy, as well as precision as amqp headers

closes #333

outputs/amqp/amqp.go

@@ -19,11 +19,24 @@ type AMQP struct {
 	Exchange string
 	// Routing Key Tag
 	RoutingTag string `toml:"routing_tag"`
+	// InfluxDB database
+	Database string
+	// InfluxDB retention policy
+	RetentionPolicy string
+	// InfluxDB precision
+	Precision string
 
 	channel *amqp.Channel
 	sync.Mutex
+	headers amqp.Table
 }
 
+const (
+	DefaultRetentionPolicy = "default"
+	DefaultDatabase        = "telegraf"
+	DefaultPrecision       = "s"
+)
+
 var sampleConfig = `
   # AMQP url
   url = "amqp://localhost:5672/influxdb"
@@ -32,11 +45,25 @@ var sampleConfig = `
   # Telegraf tag to use as a routing key
   #  ie, if this tag exists, it's value will be used as the routing key
   routing_tag = "host"
+
+  # InfluxDB retention policy
+  #retention_policy = "default"
+  # InfluxDB database
+  #database = "telegraf"
+  # InfluxDB precision
+  #precision = "s"
 `
 
 func (q *AMQP) Connect() error {
 	q.Lock()
 	defer q.Unlock()
+
+	q.headers = amqp.Table{
+		"precision":        q.Precision,
+		"database":         q.Database,
+		"retention_policy": q.RetentionPolicy,
+	}
+
 	connection, err := amqp.Dial(q.URL)
 	if err != nil {
 		return err
@@ -112,6 +139,7 @@ func (q *AMQP) Write(points []*client.Point) error {
 			false,      // mandatory
 			false,      // immediate
 			amqp.Publishing{
+				Headers:     q.headers,
 				ContentType: "text/plain",
 				Body:        bytes.Join(buf, []byte("\n")),
 			})
@@ -124,6 +152,10 @@ func (q *AMQP) Write(points []*client.Point) error {
 
 func init() {
 	outputs.Add("amqp", func() outputs.Output {
-		return &AMQP{}
+		return &AMQP{
+			Database:        DefaultDatabase,
+			Precision:       DefaultPrecision,
+			RetentionPolicy: DefaultRetentionPolicy,
+		}
 	})
 }