Include a host tag with metrics.

service/src/main/java/org/whispersystems/textsecuregcm/WhisperServerService.java

@@ -40,6 +40,8 @@ import io.micrometer.datadog.DatadogConfig;
 import io.micrometer.datadog.DatadogMeterRegistry;
 import io.micrometer.wavefront.WavefrontConfig;
 import io.micrometer.wavefront.WavefrontMeterRegistry;
+import java.net.InetAddress;
+import java.net.UnknownHostException;
 import java.net.http.HttpClient;
 import java.time.Duration;
 import java.util.ArrayList;
@@ -272,6 +274,19 @@ public class WhisperServerService extends Application<WhisperServerConfiguration
     });
 
     {
+      final String host;
+
+      {
+        String localHostName = "unknown";
+
+        try {
+          localHostName = InetAddress.getLocalHost().getHostName();
+        } catch (final UnknownHostException ignored) {
+        }
+
+        host = localHostName;
+      }
+
       final DatadogMeterRegistry datadogMeterRegistry = new DatadogMeterRegistry(new DatadogConfig() {
         @Override
         public String get(final String key) {
@@ -287,6 +302,11 @@ public class WhisperServerService extends Application<WhisperServerConfiguration
         public Duration step() {
           return config.getDatadogConfiguration().getStep();
         }
+
+        @Override
+        public String hostTag() {
+          return host;
+        }
       }, Clock.SYSTEM);
 
       datadogMeterRegistry.config().meterFilter(new MeterFilter() {