add an optional hostname override for metrics-about-metrics publication (#261)

Author: BrandonArp

src/main/java/com/arpnetworking/metrics/mad/Main.java

@@ -382,11 +382,16 @@ private Injector launchGuice(final ActorSystem actorSystem) {
             monitoringSinksBuilder.addAll(createSinks(_configuration.getMonitoringSinks()));
         }
 
-        final MetricsFactory metricsFactory = new TsdMetricsFactory.Builder()
+        final TsdMetricsFactory.Builder metricsFactoryBuilder = new TsdMetricsFactory.Builder()
                 .setClusterName(_configuration.getMonitoringCluster())
                 .setServiceName(_configuration.getMonitoringService())
-                .setSinks(monitoringSinksBuilder.build())
-                .build();
+                .setSinks(monitoringSinksBuilder.build());
+
+        if (_configuration.getMonitoringHost().isPresent()) {
+            metricsFactoryBuilder.setHostName(_configuration.getMonitoringHost().get());
+        }
+
+        final MetricsFactory metricsFactory = metricsFactoryBuilder.build();
 
         final AppShutdown shutdown = new AppShutdown();
         _guiceAppShutdown = shutdown;

src/main/java/com/arpnetworking/metrics/mad/configuration/AggregatorConfiguration.java

@@ -52,6 +52,10 @@ public String getMonitoringService() {
         return _monitoringService;
     }
 
+    public Optional<String> getMonitoringHost() {
+        return _monitoringHost;
+    }
+
     public ImmutableList<JsonNode> getMonitoringSinks() {
         return _monitoringSinks;
     }
@@ -132,6 +136,7 @@ public String toString() {
                 .add("id", Integer.toHexString(System.identityHashCode(this)))
                 .add("MonitoringCluster", _monitoringCluster)
                 .add("MonitoringService", _monitoringService)
+                .add("MonitoringHost", _monitoringHost)
                 .add("MonitoringSinks", _monitoringSinks)
                 .add("MetricsClientHost", _metricsClientHost)
                 .add("MetricsClientPort", _metricsClientPort)
@@ -172,6 +177,7 @@ private AggregatorConfiguration(final Builder builder) {
         _supplementalHttpRoutesClass = Optional.ofNullable(builder._supplementalHttpRoutesClass);
         _logDeadLetters = builder._logDeadLetters;
         _akkaConfiguration = builder._akkaConfiguration;
+        _monitoringHost = Optional.ofNullable(builder._monitoringHost);
 
         // Deprecated legacy settings
         _metricsClientHost = Optional.ofNullable(builder._metricsClientHost);
@@ -180,6 +186,7 @@ private AggregatorConfiguration(final Builder builder) {
 
     private final String _monitoringCluster;
     private final String _monitoringService;
+    private final Optional<String> _monitoringHost;
     private final ImmutableList<JsonNode> _monitoringSinks;
     private final Optional<String> _metricsClientHost;
     private final Optional<Integer> _metricsClientPort;
@@ -428,6 +435,17 @@ public Builder setSupplementalHttpRoutesClass(final Class<? extends Supplemental
             return this;
         }
 
+        /**
+         * The host to use as value for the host tag. Optional. Defaults to looking up the hostname.
+         *
+         * @param value The host to use as value for the host tag.
+         * @return This instance of {@link Builder}.
+         */
+        public Builder setMonitoringHost(final String value) {
+            _monitoringHost = value;
+            return this;
+        }
+
         /**
          * Whether to install the {@link com.arpnetworking.metrics.mad.actors.DeadLetterLogger}
          * to log all dead letter senders, recipients and messages. It differs
@@ -465,6 +483,9 @@ public Builder setAkkaConfiguration(final Map<String, ?> value) {
         @NotNull
         @NotEmpty
         private String _monitoringService = "mad";
+        @Nullable
+        @NotEmpty
+        private String _monitoringHost;
         // TODO(ville): Apply the default here once we migrate off JsonNode.
         @NotNull
         private ImmutableList<JsonNode> _monitoringSinks;