small refactor in index settings, allowing for future dynamic changes to it

modules/elasticsearch/src/main/java/org/elasticsearch/index/settings/IndexSettingsModule.java

@@ -34,6 +34,8 @@ public class IndexSettingsModule extends AbstractModule {
     }
 
     @Override protected void configure() {
-        bind(Settings.class).annotatedWith(IndexSettings.class).toInstance(settings);
+        IndexSettingsService indexSettingsService = new IndexSettingsService(settings);
+        bind(IndexSettingsService.class).toInstance(indexSettingsService);
+        bind(Settings.class).annotatedWith(IndexSettings.class).toProvider(new IndexSettingsProvider(indexSettingsService));
     }
 }

modules/elasticsearch/src/main/java/org/elasticsearch/index/settings/IndexSettingsProvider.java

@@ -0,0 +1,42 @@
+/*
+ * Licensed to Elastic Search and Shay Banon under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. Elastic Search licenses this
+ * file to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package org.elasticsearch.index.settings;
+
+import org.elasticsearch.common.inject.Inject;
+import org.elasticsearch.common.inject.Provider;
+import org.elasticsearch.common.settings.Settings;
+
+/**
+ * A wrapper around the {@link IndexSettingsService} allowing to get the current
+ * settings associated with an index (thus, allowing to change those settings and
+ * new shards will use the new settings).
+ */
+public class IndexSettingsProvider implements Provider<Settings> {
+
+    private final IndexSettingsService indexSettingsService;
+
+    @Inject public IndexSettingsProvider(IndexSettingsService indexSettingsService) {
+        this.indexSettingsService = indexSettingsService;
+    }
+
+    @Override public Settings get() {
+        return indexSettingsService.getSettings();
+    }
+}

modules/elasticsearch/src/main/java/org/elasticsearch/index/settings/IndexSettingsService.java

@@ -0,0 +1,38 @@
+/*
+ * Licensed to Elastic Search and Shay Banon under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. Elastic Search licenses this
+ * file to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package org.elasticsearch.index.settings;
+
+import org.elasticsearch.common.settings.Settings;
+
+/**
+ * A holds to the latest, updated settings for an index.
+ */
+public class IndexSettingsService {
+
+    private volatile Settings settings;
+
+    public IndexSettingsService(Settings settings) {
+        this.settings = settings;
+    }
+
+    public Settings getSettings() {
+        return this.settings;
+    }
+}