add module loading logic (untested)

core/src/main/java/org/elasticsearch/client/transport/TransportClient.java

@@ -125,7 +125,7 @@ public class TransportClient extends AbstractClient {
                     .put(CLIENT_TYPE_SETTING, CLIENT_TYPE)
                     .build();
 
-            PluginsService pluginsService = new PluginsService(settings, null, pluginClasses);
+            PluginsService pluginsService = new PluginsService(settings, null, null, pluginClasses);
             this.settings = pluginsService.updatedSettings();
 
             Version version = Version.CURRENT;

core/src/main/java/org/elasticsearch/node/Node.java

@@ -147,7 +147,7 @@ public class Node implements Releasable {
                 tmpEnv.configFile(), Arrays.toString(tmpEnv.dataFiles()), tmpEnv.logsFile(), tmpEnv.pluginsFile());
         }
 
-        this.pluginsService = new PluginsService(tmpSettings, tmpEnv.pluginsFile(), classpathPlugins);
+        this.pluginsService = new PluginsService(tmpSettings, tmpEnv.modulesFile(), tmpEnv.pluginsFile(), classpathPlugins);
         this.settings = pluginsService.updatedSettings();
         // create the environment based on the finalized (processed) view of the settings
         this.environment = new Environment(this.settings());

core/src/main/java/org/elasticsearch/plugins/PluginsService.java

@@ -89,10 +89,11 @@ public class PluginsService extends AbstractComponent {
     /**
      * Constructs a new PluginService
      * @param settings The settings of the system
+     * @param modulesDirectory The directory modules exist in, or null if modules should not be loaded from the filesystem
      * @param pluginsDirectory The directory plugins exist in, or null if plugins should not be loaded from the filesystem
      * @param classpathPlugins Plugins that exist in the classpath which should be loaded
      */
-    public PluginsService(Settings settings, Path pluginsDirectory, Collection<Class<? extends Plugin>> classpathPlugins) {
+    public PluginsService(Settings settings, Path modulesDirectory, Path pluginsDirectory, Collection<Class<? extends Plugin>> classpathPlugins) {
         super(settings);
 
         List<Tuple<PluginInfo, Plugin>> tupleBuilder = new ArrayList<>();
@@ -107,6 +108,16 @@ public class PluginsService extends AbstractComponent {
             tupleBuilder.add(new Tuple<>(pluginInfo, plugin));
         }
 
+        // load modules
+        if (modulesDirectory != null) {
+            try {
+                List<Bundle> bundles = getModuleBundles(modulesDirectory);
+                tupleBuilder.addAll(loadBundles(bundles));
+            } catch (IOException ex) {
+                throw new IllegalStateException("Unable to initialize modules", ex);
+            }
+        }
+
         // now, find all the ones that are in plugins/
         if (pluginsDirectory != null) {
             try {
@@ -262,6 +273,36 @@ public class PluginsService extends AbstractComponent {
         List<URL> urls = new ArrayList<>();
     }
 
+    // similar in impl to getPluginBundles, but DO NOT try to make them share code.
+    // we don't need to inherit all the leniency, and things are different enough.
+    static List<Bundle> getModuleBundles(Path modulesDirectory) throws IOException {
+        List<Bundle> bundles = new ArrayList<>();
+        try (DirectoryStream<Path> stream = Files.newDirectoryStream(modulesDirectory)) {
+            for (Path module : stream) {
+                if (FileSystemUtils.isHidden(module)) {
+                    continue; // skip over .DS_Store etc
+                }
+                PluginInfo info = PluginInfo.readFromProperties(module);
+                if (!info.isJvm()) {
+                    throw new IllegalStateException("modules must be jvm plugins: " + info);
+                }
+                if (!info.isIsolated()) {
+                    throw new IllegalStateException("modules must be isolated: " + info);
+                }
+                Bundle bundle = new Bundle();
+                bundle.plugins.add(info);
+                // gather urls for jar files
+                try (DirectoryStream<Path> jarStream = Files.newDirectoryStream(module, "*.jar")) {
+                    for (Path jar : jarStream) {
+                        bundle.urls.add(jar.toUri().toURL());
+                    }
+                }
+                bundles.add(bundle);
+            }
+        }
+        return bundles;
+    }
+
     static List<Bundle> getPluginBundles(Path pluginsDirectory) throws IOException {
         ESLogger logger = Loggers.getLogger(PluginsService.class);
 

core/src/test/java/org/elasticsearch/plugins/PluginsServiceTests.java

@@ -81,7 +81,7 @@ public class PluginsServiceTests extends ESTestCase {
     }
 
     static PluginsService newPluginsService(Settings settings, Class<? extends Plugin>... classpathPlugins) {
-        return new PluginsService(settings, new Environment(settings).pluginsFile(), Arrays.asList(classpathPlugins));
+        return new PluginsService(settings, null, new Environment(settings).pluginsFile(), Arrays.asList(classpathPlugins));
     }
 
     public void testAdditionalSettings() {