Add DogStatsD metrics output. (#2883)

Fixes #2490

command/server/config.go

@@ -196,6 +196,15 @@ type Telemetry struct {
 	// (e.g. a specific geo location or datacenter, dc:sfo)
 	// Default: none
 	CirconusBrokerSelectTag string `hcl:"circonus_broker_select_tag"`
+
+	// Dogstats:
+	// DogStatsdAddr is the address of a dogstatsd instance. If provided,
+	// metrics will be sent to that instance
+	DogStatsDAddr string `hcl:"dogstatsd_addr"`
+
+	// DogStatsdTags are the global tags that should be sent with each packet to dogstatsd
+	// It is a list of strings, where each string looks like "my_tag_name:my_tag_value"
+	DogStatsDTags []string `hcl:"dogstatsd_tags"`
 }
 
 func (s *Telemetry) GoString() string {
@@ -734,6 +743,8 @@ func parseTelemetry(result *Config, list *ast.ObjectList) error {
 		"circonus_broker_id",
 		"circonus_broker_select_tag",
 		"disable_hostname",
+		"dogstatsd_addr",
+		"dogstatsd_tags",
 		"statsd_address",
 		"statsite_address",
 	}

command/server/config_test.go

@@ -58,6 +58,8 @@ func TestLoadConfigFile(t *testing.T) {
 			StatsdAddr:      "bar",
 			StatsiteAddr:    "foo",
 			DisableHostname: false,
+			DogStatsDAddr:   "127.0.0.1:7254",
+			DogStatsDTags:   []string{"tag_1:val_1", "tag_2:val_2"},
 		},
 
 		DisableCache:    true,

command/server/test-fixtures/config.hcl

@@ -28,6 +28,8 @@ ha_backend "consul" {
 telemetry {
     statsd_address = "bar"
     statsite_address = "foo"
+    dogstatsd_addr = "127.0.0.1:7254"
+    dogstatsd_tags = ["tag_1:val_1", "tag_2:val_2"]
 }
 
 max_lease_ttl = "10h"