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/*
 * Druid - a distributed column store.
 * Copyright (C) 2012, 2013  Metamarkets Group Inc.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 */

package io.druid.server.coordination;

import com.fasterxml.jackson.databind.ObjectMapper;
import com.google.common.base.Throwables;
import com.google.common.util.concurrent.ThreadFactoryBuilder;
import com.metamx.common.lifecycle.LifecycleStart;
import com.metamx.common.lifecycle.LifecycleStop;
import com.metamx.emitter.EmittingLogger;
import io.druid.server.initialization.ZkPathsConfig;
import org.apache.curator.framework.CuratorFramework;
import org.apache.curator.framework.recipes.cache.ChildData;
import org.apache.curator.framework.recipes.cache.PathChildrenCache;
import org.apache.curator.framework.recipes.cache.PathChildrenCacheEvent;
import org.apache.curator.framework.recipes.cache.PathChildrenCacheListener;
import org.apache.curator.utils.ZKPaths;

import java.io.IOException;

/**
 */
public abstract class BaseZkCoordinator implements DataSegmentChangeHandler
{
  private static final EmittingLogger log = new EmittingLogger(ZkCoordinator.class);

  private final Object lock = new Object();

  private final ObjectMapper jsonMapper;
  private final ZkPathsConfig zkPaths;
  private final DruidServerMetadata me;
  private final CuratorFramework curator;

  private volatile PathChildrenCache loadQueueCache;
  private volatile boolean started;

  public BaseZkCoordinator(
      ObjectMapper jsonMapper,
      ZkPathsConfig zkPaths,
      DruidServerMetadata me,
      CuratorFramework curator
  )
  {
    this.jsonMapper = jsonMapper;
    this.zkPaths = zkPaths;
    this.me = me;
    this.curator = curator;
  }

  @LifecycleStart
  public void start() throws IOException
  {
    synchronized (lock) {
      if (started) {
        return;
      }

      log.info("Starting zkCoordinator for server[%s]", me);

      final String loadQueueLocation = ZKPaths.makePath(zkPaths.getLoadQueuePath(), me.getName());
      final String servedSegmentsLocation = ZKPaths.makePath(zkPaths.getServedSegmentsPath(), me.getName());
      final String liveSegmentsLocation = ZKPaths.makePath(zkPaths.getLiveSegmentsPath(), me.getName());

      loadQueueCache = new PathChildrenCache(
          curator,
          loadQueueLocation,
          true,
          true,
          new ThreadFactoryBuilder().setDaemon(true).setNameFormat("ZkCoordinator-%s").build()
      );

      try {
        curator.newNamespaceAwareEnsurePath(loadQueueLocation).ensure(curator.getZookeeperClient());
        curator.newNamespaceAwareEnsurePath(servedSegmentsLocation).ensure(curator.getZookeeperClient());
        curator.newNamespaceAwareEnsurePath(liveSegmentsLocation).ensure(curator.getZookeeperClient());

        loadLocalCache();

        loadQueueCache.getListenable().addListener(
            new PathChildrenCacheListener()
            {
              @Override
              public void childEvent(CuratorFramework client, PathChildrenCacheEvent event) throws Exception
              {
                final ChildData child = event.getData();
                switch (event.getType()) {
                  case CHILD_ADDED:
                    final String path = child.getPath();
                    final DataSegmentChangeRequest segment = jsonMapper.readValue(
                        child.getData(), DataSegmentChangeRequest.class
                    );

                    log.info("New node[%s] with segmentClass[%s]", path, segment.getClass());

                    try {
                      segment.go(
                          getDataSegmentChangeHandler(),
                          new DataSegmentChangeCallback()
                          {
                            boolean hasRun = false;

                            @Override
                            public void execute()
                            {
                              try {
                                if (!hasRun) {
                                  curator.delete().guaranteed().forPath(path);
                                  log.info("Completed processing for node[%s]", path);
                                  hasRun = true;
                                }
                              }
                              catch (Exception e) {
                                throw Throwables.propagate(e);
                              }
                            }
                          }
                      );
                    }
                    catch (Exception e) {
                      try {
                        curator.delete().guaranteed().forPath(path);
                      }
                      catch (Exception e1) {
                        log.info(e1, "Failed to delete node[%s], but ignoring exception.", path);
                      }

                      log.makeAlert(e, "Segment load/unload: uncaught exception.")
                         .addData("node", path)
                         .addData("nodeProperties", segment)
                         .emit();
                    }

                    break;
                  case CHILD_REMOVED:
                    log.info("%s was removed", event.getData().getPath());
                    break;
                  default:
                    log.info("Ignoring event[%s]", event);
                }
              }
            }
        );
        loadQueueCache.start();
      }
      catch (Exception e) {
        Throwables.propagateIfPossible(e, IOException.class);
        throw Throwables.propagate(e);
      }

      started = true;
    }
  }

  @LifecycleStop
  public void stop()
  {
    log.info("Stopping ZkCoordinator for [%s]", me);
    synchronized (lock) {
      if (!started) {
        return;
      }

      try {
        loadQueueCache.close();
      }
      catch (Exception e) {
        throw Throwables.propagate(e);
      }
      finally {
        loadQueueCache = null;
        started = false;
      }
    }
  }

  public abstract void loadLocalCache();

  public abstract DataSegmentChangeHandler getDataSegmentChangeHandler();
}