Allow users to tell telegraf Agent not to include host tag

closes #848

agent/agent.go

@@ -27,17 +27,19 @@ func NewAgent(config *config.Config) (*Agent, error) {
 		Config: config,
 	}
 
-	if a.Config.Agent.Hostname == "" {
-		hostname, err := os.Hostname()
-		if err != nil {
-			return nil, err
+	if !a.Config.Agent.OmitHostname {
+		if a.Config.Agent.Hostname == "" {
+			hostname, err := os.Hostname()
+			if err != nil {
+				return nil, err
+			}
+
+			a.Config.Agent.Hostname = hostname
 		}
 
-		a.Config.Agent.Hostname = hostname
+		config.Tags["host"] = a.Config.Agent.Hostname
 	}
 
-	config.Tags["host"] = a.Config.Agent.Hostname
-
 	return a, nil
 }
 

agent/agent_test.go

@@ -1,7 +1,6 @@
 package agent
 
 import (
-	"github.com/stretchr/testify/assert"
 	"testing"
 	"time"
 
@@ -11,8 +10,18 @@ import (
 	_ "github.com/influxdata/telegraf/plugins/inputs/all"
 	// needing to load the outputs
 	_ "github.com/influxdata/telegraf/plugins/outputs/all"
+
+	"github.com/stretchr/testify/assert"
 )
 
+func TestAgent_OmitHostname(t *testing.T) {
+	c := config.NewConfig()
+	c.Agent.OmitHostname = true
+	_, err := NewAgent(c)
+	assert.NoError(t, err)
+	assert.NotContains(t, c.Tags, "host")
+}
+
 func TestAgent_LoadPlugin(t *testing.T) {
 	c := config.NewConfig()
 	c.InputFilters = []string{"mysql"}