content: /*
   * Licensed to the Apache Software Foundation (ASF) under one
   * or more contributor license agreements.  See the NOTICE file
   * distributed with this work for additional information
   * regarding copyright ownership.  The ASF 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.apache.distributedlog.feature;
  
  import static com.google.common.base.Preconditions.checkNotNull;
  
  import com.google.common.collect.Lists;
  import com.google.common.util.concurrent.ThreadFactoryBuilder;
  import java.io.File;
  import java.io.IOException;
  import java.util.List;
  import java.util.Map;
  import java.util.concurrent.ConcurrentHashMap;
  import java.util.concurrent.ConcurrentMap;
  import java.util.concurrent.Executors;
  import java.util.concurrent.ScheduledExecutorService;
  import java.util.concurrent.TimeUnit;
  import org.apache.bookkeeper.feature.Feature;
  import org.apache.bookkeeper.feature.FeatureProvider;
  import org.apache.bookkeeper.feature.SettableFeature;
  import org.apache.bookkeeper.stats.StatsLogger;
  import org.apache.commons.configuration2.ex.ConfigurationException;
  import org.apache.distributedlog.DistributedLogConfiguration;
  import org.apache.distributedlog.common.config.ConcurrentBaseConfiguration;
  import org.apache.distributedlog.common.config.ConfigurationListener;
  import org.apache.distributedlog.common.config.ConfigurationSubscription;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  
  /**
   * Feature Provider based dynamic configuration.
   */
  public class DynamicConfigurationFeatureProvider extends AbstractFeatureProvider
          implements ConfigurationListener {
      private static final Logger logger = LoggerFactory.getLogger(DynamicConfigurationFeatureProvider.class);
  
  
      private final ConcurrentBaseConfiguration featuresConf;
      private ConfigurationSubscription featuresConfSubscription;
      private final ConcurrentMap<String, SettableFeature> features;
      private final ScheduledExecutorService executorService;
  
      public DynamicConfigurationFeatureProvider(String rootScope,
                                                 DistributedLogConfiguration conf,
                                                 StatsLogger statsLogger) {
          super(rootScope, conf, statsLogger);
          this.features = new ConcurrentHashMap<String, SettableFeature>();
          this.featuresConf = new ConcurrentBaseConfiguration();
          this.executorService = Executors.newSingleThreadScheduledExecutor(
                  new ThreadFactoryBuilder().setNameFormat("DynamicConfigurationFeatureProvider-%d").build());
      }
  
      ConcurrentBaseConfiguration getFeatureConf() {
          return featuresConf;
      }
  
      ConfigurationSubscription getFeatureConfSubscription() {
          return featuresConfSubscription;
      }
  
      @Override
      public void start() throws IOException {
          List<File> configFiles =
                  Lists.newArrayListWithExpectedSize(2);
          String baseConfigPath = conf.getFileFeatureProviderBaseConfigPath();
          checkNotNull(baseConfigPath);
          File baseConfigFile = new File(baseConfigPath);
          configFiles.add(baseConfigFile);
          String overlayConfigPath = conf.getFileFeatureProviderOverlayConfigPath();
          if (null != overlayConfigPath) {
              File overlayConfigFile = new File(overlayConfigPath);
              configFiles.add(overlayConfigFile);
          }
          try {
              this.featuresConfSubscription = new ConfigurationSubscription(
                      this.featuresConf,
                      configFiles,
                      executorService,
                      conf.getDynamicConfigReloadIntervalSec(),
                      TimeUnit.SECONDS);
          } catch (ConfigurationException e) {
              throw new IOException("Failed to register subscription on features configuration");
          }
          this.featuresConfSubscription.registerListener(this);
      }
  
      @Override
      public void stop() {
          this.executorService.shutdown();
      }
  
      @Override
      public void onReload(ConcurrentBaseConfiguration conf) {
          for (Map.Entry<String, SettableFeature> feature : features.entrySet()) {
              String featureName = feature.getKey();
              int availability = conf.getInt(featureName, 0);
              if (availability != feature.getValue().availability()) {
                  feature.getValue().set(availability);
                  logger.info("Reload feature {}={}", featureName, availability);
              }
          }
      }
  
      @Override
      protected Feature makeFeature(String featureName) {
          return ConfigurationFeatureProvider.makeFeature(
                  featuresConf, features, featureName);
      }
  
      @Override
      protected FeatureProvider makeProvider(String fullScopeName) {
          return new ConfigurationFeatureProvider(
                  fullScopeName, featuresConf, features);
      }
  }
  