fhan688 commented on code in PR #19728: URL: https://github.com/apache/hudi/pull/19728#discussion_r3862915721
########## hudi-flink-datasource/hudi-flink/src/main/java/org/apache/hudi/sink/buffer/PreemptiveMemorySegmentPool.java: ########## @@ -0,0 +1,126 @@ +/* + * 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.hudi.sink.buffer; + +import org.apache.hudi.common.util.ValidationUtils; + +import org.apache.flink.core.memory.MemorySegment; +import org.apache.flink.table.runtime.util.MemorySegmentPool; + +import javax.annotation.Nullable; + +import java.io.Closeable; +import java.io.IOException; +import java.util.List; + +/** + * A {@link MemorySegmentPool} wrapper that can reclaim pages from an inactive owner when the + * delegate pool is exhausted. + * + * <p>The owner represents the bucket whose buffer is currently requesting pages. The reclaimer + * must never reclaim that owner because the request may occur in the middle of serializing a row. + * If no other owner can release pages, this pool returns {@code null} and lets the caller handle + * the allocation failure. + */ +public class PreemptiveMemorySegmentPool implements MemorySegmentPool, Closeable { + + /** Callback that reclaims memory from an owner other than the excluded in-flight owner. */ + @FunctionalInterface + public interface MemoryReclaimer { + /** + * Reclaims memory from an inactive owner. + * + * @param excludedOwnerId the owner currently requesting a page + * @return {@code true} if memory was reclaimed and allocation should be retried + */ + boolean reclaim(String excludedOwnerId); + } + + private final MemorySegmentPool delegate; + private final MemoryReclaimer memoryReclaimer; + + @Nullable + private String currentOwnerId; + private boolean preempting; Review Comment: > Is `preempting` flag necessary, Could you clarify the purpose of the flag or add some comments. Yes, the flag is needed as a re-entrancy guard. The reclamation callback flushes and disposes a victim while that victim may still be registered. If the callback path transitively requests another page, re-entering the reclaimer could select and flush the same victim recursively. I kept the flag and added comments to clarify both its purpose and the guarded branch in `nextSegment()`. This behavior is also covered by `testRetriesAllocationOnceWithoutNestedPreemption`. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
