HBASE-8702: Make WALEditCodec pluggable

git-svn-id: https://svn.apache.org/repos/asf/hbase/trunk@1492407 13f79535-47bb-0310-9956-ffa450edef68

hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/wal/ProtobufLogReader.java

@@ -175,7 +175,7 @@ public class ProtobufLogReader extends ReaderBase {
 
   @Override
   protected void initAfterCompression() throws IOException {
-    WALCellCodec codec = new WALCellCodec(this.compressionContext);
+    WALCellCodec codec = WALCellCodec.create(this.conf, this.compressionContext);
     this.cellDecoder = codec.getDecoder(this.inputStream);
     if (this.hasCompression) {
       this.byteStringUncompressor = codec.getByteStringUncompressor();

hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/wal/ProtobufLogWriter.java

@@ -80,7 +80,7 @@ public class ProtobufLogWriter implements HLog.Writer {
     output.write(ProtobufLogReader.PB_WAL_MAGIC);
     WALHeader.newBuilder().setHasCompression(doCompress).build().writeDelimitedTo(output);
 
-    WALCellCodec codec = new WALCellCodec(this.compressionContext);
+    WALCellCodec codec = WALCellCodec.create(conf, this.compressionContext);
     this.cellEncoder = codec.getEncoder(this.output);
     if (doCompress) {
       this.compressor = codec.getByteStringCompressor();

hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/wal/WALCellCodec.java

@@ -22,6 +22,7 @@ import java.io.IOException;
 import java.io.InputStream;
 import java.io.OutputStream;
 
+import org.apache.hadoop.conf.Configuration;
 import org.apache.hadoop.hbase.Cell;
 import org.apache.hadoop.hbase.KeyValue;
 import org.apache.hadoop.hbase.codec.BaseDecoder;
@@ -29,6 +30,7 @@ import org.apache.hadoop.hbase.codec.BaseEncoder;
 import org.apache.hadoop.hbase.codec.Codec;
 import org.apache.hadoop.hbase.codec.KeyValueCodec;
 import org.apache.hadoop.hbase.util.Bytes;
+import org.apache.hadoop.hbase.util.ReflectionUtils;
 
 import com.google.common.base.Preconditions;
 import com.google.protobuf.ByteString;
@@ -39,6 +41,9 @@ import com.google.protobuf.ByteString;
  * This is a pure coincidence... they are independent and don't have to be compatible.
  */
 public class WALCellCodec implements Codec {
+  /** Configuration key for the class to use when encoding cells in the WAL */
+  public static final String WAL_CELL_CODEC_CLASS_KEY = "hbase.regionserver.wal.codec";
+
   private final CompressionContext compression;
   private final ByteStringUncompressor statelessUncompressor = new ByteStringUncompressor() {
     @Override
@@ -47,10 +52,33 @@ public class WALCellCodec implements Codec {
     }
   };
 
-  public WALCellCodec(CompressionContext compression) {
+  /**
+   * Default constructor - <b>all subclasses must implement a constructor with this signature </b>
+   * if they are to be dynamically loaded from the {@link Configuration}.
+   * @param conf configuration to configure <tt>this</tt>
+   * @param compression compression the codec should support, can be <tt>null</tt> to indicate no
+   *          compression
+   */
+  public WALCellCodec(Configuration conf, CompressionContext compression) {
     this.compression = compression;
   }
 
+  /**
+   * Create and setup a {@link WALCellCodec} from the {@link Configuration} and CompressionContext,
+   * if they have been specified. Fully prepares the codec for use.
+   * @param conf {@link Configuration} to read for the user-specified codec. If none is specified,
+   *          uses a {@link WALCellCodec}.
+   * @param compression compression the codec should use
+   * @return a {@link WALCellCodec} ready for use.
+   * @throws UnsupportedOperationException if the codec cannot be instantiated
+   */
+  public static WALCellCodec create(Configuration conf, CompressionContext compression)
+      throws UnsupportedOperationException {
+    String className = conf.get(WAL_CELL_CODEC_CLASS_KEY, WALCellCodec.class.getName());
+    return ReflectionUtils.instantiateWithCustomCtor(className, new Class[] { Configuration.class,
+        CompressionContext.class }, new Object[] { conf, compression });
+  }
+
   public interface ByteStringCompressor {
     ByteString compress(byte[] data, Dictionary dict) throws IOException;
   }

hbase-server/src/test/java/org/apache/hadoop/hbase/regionserver/wal/TestCustomWALCellCodec.java

@@ -0,0 +1,62 @@
+/**
+ * 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.regionserver.wal;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+
+import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.hbase.HConstants;
+import org.apache.hadoop.hbase.SmallTests;
+import org.junit.Test;
+import org.junit.experimental.categories.Category;
+
+/**
+ * Test that we can create, load, setup our own custom codec
+ */
+@Category(SmallTests.class)
+public class TestCustomWALCellCodec {
+
+  public static class CustomWALCellCodec extends WALCellCodec {
+    public Configuration conf;
+    public CompressionContext context;
+
+    public CustomWALCellCodec(Configuration conf, CompressionContext compression) {
+      super(conf, compression);
+      this.conf = conf;
+      this.context = compression;
+    }
+  }
+
+  /**
+   * Test that a custom {@link WALCellCodec} will be completely setup when it is instantiated via
+   * {@link WALCellCodec}
+   * @throws Exception on failure
+   */
+  @Test
+  public void testCreatePreparesCodec() throws Exception {
+    Configuration conf = new Configuration(false);
+    conf.setClass(WALCellCodec.WAL_CELL_CODEC_CLASS_KEY, CustomWALCellCodec.class,
+      WALCellCodec.class);
+    CustomWALCellCodec codec = (CustomWALCellCodec) WALCellCodec.create(conf, null);
+    assertEquals("Custom codec didn't get initialized with the right configuration!", conf,
+      codec.conf);
+    assertEquals("Custom codec didn't get initialized with the right compression context!", null,
+      codec.context);
+  }
+}