add handlebars resolve hostname helper

BaragonAgentService/src/main/java/com/hubspot/baragon/agent/BaragonAgentServiceModule.java

@@ -29,6 +29,7 @@
 import com.hubspot.baragon.agent.handlebars.FormatTimestampHelper;
 import com.hubspot.baragon.agent.handlebars.IfEqualHelperSource;
 import com.hubspot.baragon.agent.handlebars.PreferSameRackWeightingHelper;
+import com.hubspot.baragon.agent.handlebars.ResolveHostnameHelper;
 import com.hubspot.baragon.agent.listeners.ResyncListener;
 import com.hubspot.baragon.agent.models.FilePathFormatType;
 import com.hubspot.baragon.agent.models.LbConfigTemplate;
@@ -75,9 +76,10 @@ protected void configure() {
   public Handlebars providesHandlebars(BaragonAgentConfiguration config, BaragonAgentMetadata agentMetadata) {
     final Handlebars handlebars = new Handlebars();
 
-    handlebars.registerHelper("formatTimestamp", new FormatTimestampHelper(config.getDefaultDateFormat()));
-    handlebars.registerHelper("firstOf", new FirstOfHelper(""));
-    handlebars.registerHelper("currentRackIsPresent", new CurrentRackIsPresentHelper(agentMetadata.getEc2().getAvailabilityZone()));
+    handlebars.registerHelper(FormatTimestampHelper.NAME, new FormatTimestampHelper(config.getDefaultDateFormat()));
+    handlebars.registerHelper(FirstOfHelper.NAME, new FirstOfHelper(""));
+    handlebars.registerHelper(CurrentRackIsPresentHelper.NAME, new CurrentRackIsPresentHelper(agentMetadata.getEc2().getAvailabilityZone()));
+    handlebars.registerHelper(ResolveHostnameHelper.NAME, new ResolveHostnameHelper());
     handlebars.registerHelpers(new PreferSameRackWeightingHelper(config, agentMetadata));
     handlebars.registerHelpers(IfEqualHelperSource.class);
 

BaragonAgentService/src/main/java/com/hubspot/baragon/agent/handlebars/CurrentRackIsPresentHelper.java

@@ -9,6 +9,8 @@
 import com.hubspot.baragon.models.UpstreamInfo;
 
 public class CurrentRackIsPresentHelper implements Helper<Collection<UpstreamInfo>> {
+  public static final String NAME = "currentRackIsPresent";
+
   private final Optional<String> currentRackId;
 
   public CurrentRackIsPresentHelper(Optional<String> currentRackId) {

BaragonAgentService/src/main/java/com/hubspot/baragon/agent/handlebars/FirstOfHelper.java

@@ -8,6 +8,8 @@
 import com.google.common.base.Strings;
 
 public class FirstOfHelper implements Helper<Object> {
+  public static final String NAME = "firstOf";
+
   private final Object fallback;
 
   public FirstOfHelper(Object fallback) {

BaragonAgentService/src/main/java/com/hubspot/baragon/agent/handlebars/FormatTimestampHelper.java

@@ -11,6 +11,7 @@
 
 public class FormatTimestampHelper implements Helper<Number> {
   private static final Logger LOG = LoggerFactory.getLogger(FormatTimestampHelper.class);
+  public static final String NAME = "formatTimestamp";
 
   private final String defaultFormatString;
 

BaragonAgentService/src/main/java/com/hubspot/baragon/agent/handlebars/ResolveHostnameHelper.java

@@ -0,0 +1,25 @@
+package com.hubspot.baragon.agent.handlebars;
+
+import java.net.InetAddress;
+import java.net.InetSocketAddress;
+import java.net.UnknownHostException;
+
+import com.github.jknack.handlebars.Helper;
+import com.github.jknack.handlebars.Options;
+import com.google.common.net.HostAndPort;
+
+public class ResolveHostnameHelper implements Helper<String> {
+
+  public static final String NAME = "resolveHostname";
+
+  @Override
+  public CharSequence apply(String address, Options options) throws UnknownHostException {
+    if (address.contains(":")) {
+      HostAndPort hostAndPort = HostAndPort.fromString(address);
+      InetSocketAddress socketAddress = new InetSocketAddress(InetAddress.getByName(hostAndPort.getHostText()), hostAndPort.getPort());
+      return String.format("%s:%d", socketAddress.getAddress().getHostAddress(), socketAddress.getPort());
+    } else {
+      return InetAddress.getByName(address).getHostAddress();
+    }
+  }
+}