| /* |
| * |
| * 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.coprocessor; |
| |
| import java.io.IOException; |
| |
| import org.apache.hadoop.fs.Path; |
| import org.apache.hadoop.hbase.HBaseInterfaceAudience; |
| import org.apache.hadoop.hbase.client.RegionInfo; |
| import org.apache.hadoop.hbase.wal.WALEdit; |
| import org.apache.hadoop.hbase.wal.WALKey; |
| import org.apache.yetus.audience.InterfaceAudience; |
| import org.apache.yetus.audience.InterfaceStability; |
| |
| /** |
| * It's provided to have a way for coprocessors to observe, rewrite, |
| * or skip WALEdits as they are being written to the WAL. |
| * |
| * Note that implementers of WALObserver will not see WALEdits that report themselves |
| * as empty via {@link WALEdit#isEmpty()}. |
| * |
| * {@link org.apache.hadoop.hbase.coprocessor.RegionObserver} provides |
| * hooks for adding logic for WALEdits in the region context during reconstruction. |
| * |
| * Defines coprocessor hooks for interacting with operations on the |
| * {@link org.apache.hadoop.hbase.wal.WAL}. |
| * |
| * Since most implementations will be interested in only a subset of hooks, this class uses |
| * 'default' functions to avoid having to add unnecessary overrides. When the functions are |
| * non-empty, it's simply to satisfy the compiler by returning value of expected (non-void) type. |
| * It is done in a way that these default definitions act as no-op. So our suggestion to |
| * implementation would be to not call these 'default' methods from overrides. |
| * <br><br> |
| * |
| * <h3>Exception Handling</h3> |
| * For all functions, exception handling is done as follows: |
| * <ul> |
| * <li>Exceptions of type {@link IOException} are reported back to client.</li> |
| * <li>For any other kind of exception: |
| * <ul> |
| * <li>If the configuration {@link CoprocessorHost#ABORT_ON_ERROR_KEY} is set to true, then |
| * the server aborts.</li> |
| * <li>Otherwise, coprocessor is removed from the server and |
| * {@link org.apache.hadoop.hbase.DoNotRetryIOException} is returned to the client.</li> |
| * </ul> |
| * </li> |
| * </ul> |
| */ |
| @InterfaceAudience.LimitedPrivate(HBaseInterfaceAudience.COPROC) |
| @InterfaceStability.Evolving |
| public interface WALObserver { |
| /** |
| * Called before a {@link WALEdit} |
| * is writen to WAL. |
| * Do not amend the WALKey. It is InterfaceAudience.Private. Changing the WALKey will cause |
| * damage. |
| * @deprecated Since hbase-2.0.0. To be replaced with an alternative that does not expose |
| * InterfaceAudience classes such as WALKey and WALEdit. Will be removed in hbase-3.0.0. |
| */ |
| @Deprecated |
| default void preWALWrite(ObserverContext<? extends WALCoprocessorEnvironment> ctx, |
| RegionInfo info, WALKey logKey, WALEdit logEdit) throws IOException {} |
| |
| /** |
| * Called after a {@link WALEdit} |
| * is writen to WAL. |
| * Do not amend the WALKey. It is InterfaceAudience.Private. Changing the WALKey will cause |
| * damage. |
| * @deprecated Since hbase-2.0.0. To be replaced with an alternative that does not expose |
| * InterfaceAudience classes such as WALKey and WALEdit. Will be removed in hbase-3.0.0. |
| */ |
| @Deprecated |
| default void postWALWrite(ObserverContext<? extends WALCoprocessorEnvironment> ctx, |
| RegionInfo info, WALKey logKey, WALEdit logEdit) throws IOException {} |
| |
| /** |
| * Called before rolling the current WAL |
| * @param oldPath the path of the current wal that we are replacing |
| * @param newPath the path of the wal we are going to create |
| */ |
| default void preWALRoll(ObserverContext<? extends WALCoprocessorEnvironment> ctx, |
| Path oldPath, Path newPath) throws IOException {} |
| |
| /** |
| * Called after rolling the current WAL |
| * @param oldPath the path of the wal that we replaced |
| * @param newPath the path of the wal we have created and now is the current |
| */ |
| default void postWALRoll(ObserverContext<? extends WALCoprocessorEnvironment> ctx, |
| Path oldPath, Path newPath) throws IOException {} |
| } |
| |