Do not load extensions on each call

server/src/main/java/io/druid/initialization/Initialization.java

@@ -101,6 +101,16 @@ public class Initialization
       "io.druid",
       "com.metamx.druid"
   );
+  private static List loadedDruidModules = Lists.newArrayList();
+
+  /**
+  * @return List of {@link DruidModule}, once loaded.
+  */
+  public static List getLoadedDruidModules()
+  {
+    return loadedDruidModules;
+  }
+  
 
   public synchronized static <T> List<T> getFromExtensions(ExtensionsConfig config, Class<T> clazz)
   {
@@ -131,6 +141,10 @@ public class Initialization
       }
     }
 
+    if (clazz.equals(DruidModule.class)){
+      loadedDruidModules.addAll(retVal);
+    }
+
     return retVal;
   }
 

server/src/main/java/io/druid/server/StatusResource.java

@@ -19,12 +19,16 @@
 
 package io.druid.server;
 
+import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.annotation.JsonProperty;
+import io.druid.initialization.DruidModule;
 import io.druid.initialization.Initialization;
 
 import javax.ws.rs.GET;
 import javax.ws.rs.Path;
 import javax.ws.rs.Produces;
+import java.util.ArrayList;
+import java.util.List;
 
 /**
  */
@@ -42,20 +46,42 @@ public class StatusResource
   {
     return new Status(
         Initialization.class.getPackage().getImplementationVersion(),
+        getExtensionVersions(),
         new Memory(Runtime.getRuntime())
     );
   }
 
+  /**
+   * Load the unique extensions and return their implementation-versions
+   *
+   * @return map of extensions loaded with their respective implementation versions.
+   */
+  private static List<ModuleVersion> getExtensionVersions()
+  {
+    final List<DruidModule> druidModules = Initialization.getLoadedDruidModules();
+
+    List<ModuleVersion> moduleVersions = new ArrayList<>();
+    for (DruidModule module : druidModules) {
+      String artifact = module.getClass().getPackage().getImplementationTitle();
+      String version = module.getClass().getPackage().getImplementationVersion();
+
+      moduleVersions.add(new ModuleVersion(module.getClass().getCanonicalName(), artifact, version));
+    }
+    return moduleVersions;
+  }
+
   public static class Status
   {
     final String version;
+    final List<ModuleVersion> modules;
     final Memory memory;
 
     public Status(
-        String version, Memory memory
+        String version, List<ModuleVersion> modules, Memory memory
     )
     {
       this.version = version;
+      this.modules = modules;
       this.memory = memory;
     }
 
@@ -65,6 +91,12 @@ public class StatusResource
       return version;
     }
 
+    @JsonProperty
+    public List<ModuleVersion> getModules()
+    {
+      return modules;
+    }
+
     @JsonProperty
     public Memory getMemory()
     {
@@ -75,21 +107,29 @@ public class StatusResource
     public String toString()
     {
       final String NL = System.getProperty("line.separator");
-      return String.format("Druid version - %s", version) + NL;
+      StringBuilder output = new StringBuilder();
+      output.append(String.format("Druid version - %s", version)).append(NL).append(NL);
+
+      if (modules.size() > 0) {
+        output.append("Registered Druid Modules").append(NL);
+      } else {
+        output.append("No Druid Modules loaded !");
+      }
+
+      for (ModuleVersion moduleVersion : modules) {
+        output.append(moduleVersion).append(NL);
+      }
+      return output.toString();
     }
   }
 
+  @JsonInclude(JsonInclude.Include.NON_NULL)
   public static class ModuleVersion
   {
     final String name;
     final String artifact;
     final String version;
 
-    public ModuleVersion(String name)
-    {
-      this(name, "", "");
-    }
-
     public ModuleVersion(String name, String artifact, String version)
     {
       this.name = name;