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package org.apache.impala.catalog.events;

import java.util.Collections;
import java.util.List;
import org.apache.hadoop.hive.metastore.api.CurrentNotificationEventId;
import org.apache.hadoop.hive.metastore.api.NotificationEvent;
import org.apache.hadoop.hive.metastore.api.NotificationEventResponse;
import org.apache.impala.catalog.CatalogException;
import org.apache.impala.catalog.CatalogServiceCatalog;
import org.apache.impala.catalog.MetaStoreClientPool.MetaStoreClient;
import org.apache.thrift.TException;

/**
 * A test MetastoreEventProcessor which executes in the same thread. Useful for testing
 * functionality of MetastoreEventsProcessor
 */
public class SynchronousHMSEventProcessorForTests extends MetastoreEventsProcessor {
  SynchronousHMSEventProcessorForTests(
      CatalogServiceCatalog catalog, long startSyncFromId, long pollingFrequencyInSec)
          throws CatalogException {
    super(catalog, startSyncFromId, pollingFrequencyInSec);
  }

  @Override
  public void startScheduler() {
    // nothing to do here; there is no background thread for this processor
  }

  public List<NotificationEvent> getNextNotificationEvents(long eventId)
      throws MetastoreNotificationFetchException {
    try (MetaStoreClient msClient = catalog_.getMetaStoreClient()) {
      // fetch the current notification event id. We assume that the polling interval
      // is small enough that most of these polling operations result in zero new
      // events. In such a case, fetching current notification event id is much faster
      // (and cheaper on HMS side) instead of polling for events directly
      CurrentNotificationEventId currentNotificationEventId =
          msClient.getHiveClient().getCurrentNotificationEventId();
      long currentEventId = currentNotificationEventId.getEventId();

      // no new events since we last polled
      if (currentEventId <= eventId) {
        return Collections.emptyList();
      }

      NotificationEventResponse response = msClient.getHiveClient()
          .getNextNotification(eventId, 1000, null);
      return response.getEvents();
    } catch (TException e) {
      throw new MetastoreNotificationFetchException(
          "Unable to fetch notifications from metastore", e);
    }
  }
}