/*
 * 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.hadoop.hbase.replication;

import org.apache.hadoop.hbase.HBaseInterfaceAudience;
import org.apache.hadoop.hbase.wal.WAL.Entry;
import org.apache.yetus.audience.InterfaceAudience;

/**
 * A Filter for WAL entries before being sent over to replication. Multiple filters might be chained
 * together using {@link ChainWALEntryFilter}. Applied on the replication source side.
 * <p>
 * There is also a filter that can be installed on the sink end of a replication stream. See
 * {@link org.apache.hadoop.hbase.replication.regionserver.WALEntrySinkFilter}. Certain use-cases
 * may need such a facility but better to filter here on the source side rather than later, after
 * the edit arrives at the sink.
 * </p>
 * @see org.apache.hadoop.hbase.replication.regionserver.WALEntrySinkFilter for filtering
 *      replication on the sink-side.
 */
@InterfaceAudience.LimitedPrivate(HBaseInterfaceAudience.REPLICATION)
public interface WALEntryFilter {
  /**
   * <p>
   * Applies the filter, possibly returning a different Entry instance. If null is returned, the
   * entry will be skipped.
   * </p>
   * <p>
   * Notice that you are free to modify the cell list of the give entry, but do not change the
   * content of the cell, it may be used by others at the same time(and usually you can not modify a
   * cell unless you cast it to the implementation class, which is not a good idea).
   * </p>
   * @param entry Entry to filter
   * @return a (possibly modified) Entry to use. Returning null or an entry with no cells will cause
   *         the entry to be skipped for replication.
   */
  Entry filter(Entry entry);

  /**
   * Tell the filter whether the peer is a serial replication peer.
   * <p>
   * For serial replication, usually you should not filter out an entire entry, unless the peer
   * config does not contain the table, because we need the region name and sequence id of the entry
   * to advance the pushed sequence id, otherwise the replication may be blocked. You can just
   * filter out all the cells of the entry to stop it being replicated to peer cluster,or just rely
   * on the {@link WALCellFilter#filterCell(Entry, org.apache.hadoop.hbase.Cell)} method to filter
   * all the cells out.
   * @param serial {@code true} if the peer is a serial replication peer, otherwise {@code false}
   */
  default void setSerial(boolean serial) {
  }
}
