[GitHub] [lucene] danmuzi commented on a diff in pull request #11796: GITHUB#11795: Add FilterDirectory to track write amplification factor

[GitBox <gi...@apache.org>]

danmuzi commented on code in PR #11796:
URL: https://github.com/apache/lucene/pull/11796#discussion_r983858651


##########
lucene/misc/src/java/org/apache/lucene/misc/store/ByteWritesTrackingDirectoryWrapper.java:
##########
@@ -0,0 +1,102 @@
+/*
+ * 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.lucene.misc.store;
+
+import java.io.IOException;
+import java.util.concurrent.atomic.AtomicLong;
+import org.apache.lucene.store.Directory;
+import org.apache.lucene.store.FilterDirectory;
+import org.apache.lucene.store.IOContext;
+import org.apache.lucene.store.IndexOutput;
+
+/** {@link FilterDirectory} that tracks write amplification factor */
+public final class ByteWritesTrackingDirectoryWrapper extends FilterDirectory {
+
+  private final AtomicLong flushedBytes = new AtomicLong();
+  private final AtomicLong mergedBytes = new AtomicLong();
+  public final boolean trackTempOutput;
+
+  public ByteWritesTrackingDirectoryWrapper(Directory in) {
+    this(in, false);
+  }
+  /**
+   * Constructor with option to track tempOutput
+   *
+   * @param in input Directory
+   * @param trackTempOutput if true, will also track temporary outputs created by this directory
+   */
+  public ByteWritesTrackingDirectoryWrapper(Directory in, boolean trackTempOutput) {
+    super(in);
+    this.trackTempOutput = trackTempOutput;
+  }
+
+  @Override
+  public IndexOutput createOutput(String name, IOContext ioContext) throws IOException {
+    IndexOutput output = in.createOutput(name, ioContext);
+    ByteTrackingIndexOutput byteTrackingIndexOutput;
+    if (ioContext.context.equals(IOContext.Context.FLUSH)) {
+      byteTrackingIndexOutput = new ByteTrackingIndexOutput(output, flushedBytes);
+    } else if (ioContext.context.equals(IOContext.Context.MERGE)) {
+      byteTrackingIndexOutput = new ByteTrackingIndexOutput(output, mergedBytes);
+    } else {
+      return output;
+    }
+    return byteTrackingIndexOutput;
+  }
+
+  @Override
+  public IndexOutput createTempOutput(String prefix, String suffix, IOContext ioContext)
+      throws IOException {
+    IndexOutput output = in.createTempOutput(prefix, suffix, ioContext);
+    if (trackTempOutput) {
+      ByteTrackingIndexOutput byteTrackingIndexOutput;
+      if (ioContext.context.equals(IOContext.Context.FLUSH)) {
+        byteTrackingIndexOutput = new ByteTrackingIndexOutput(output, flushedBytes);
+      } else if (ioContext.context.equals(IOContext.Context.MERGE)) {
+        byteTrackingIndexOutput = new ByteTrackingIndexOutput(output, mergedBytes);
+      } else {
+        return output;
+      }
+      return byteTrackingIndexOutput;

Review Comment:
   There are duplicate codes.
   How about changing it to:
   ```java
     @Override
     public IndexOutput createOutput(String name, IOContext ioContext) throws IOException {
       IndexOutput output = in.createOutput(name, ioContext);
       return createByteTrackingOutput(output, ioContext.context);
     }
   
     @Override
     public IndexOutput createTempOutput(String prefix, String suffix, IOContext ioContext)
         throws IOException {
       IndexOutput output = in.createTempOutput(prefix, suffix, ioContext);
       return trackTempOutput ? createByteTrackingOutput(output, ioContext.context) : output;
     }
   
     private IndexOutput createByteTrackingOutput(IndexOutput output, IOContext.Context context) {
      // If you want to add this feature to Lucene 9, you should modify it to the old switch-case style.
       return switch (context) {
         case FLUSH -> new ByteTrackingIndexOutput(output, flushedBytes);
         case MERGE -> new ByteTrackingIndexOutput(output, mergedBytes);
         default -> output;
       };
     }
   ```



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