hachikuji commented on a change in pull request #9418: URL: https://github.com/apache/kafka/pull/9418#discussion_r509723127
########## File path: raft/src/main/java/org/apache/kafka/raft/internals/BatchAccumulator.java ########## @@ -0,0 +1,296 @@ +/* + * 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.kafka.raft.internals; + +import org.apache.kafka.common.memory.MemoryPool; +import org.apache.kafka.common.record.CompressionType; +import org.apache.kafka.common.record.MemoryRecords; +import org.apache.kafka.common.record.RecordBatch; +import org.apache.kafka.common.utils.Time; +import org.apache.kafka.common.utils.Timer; +import org.apache.kafka.raft.RecordSerde; + +import java.io.Closeable; +import java.nio.ByteBuffer; +import java.util.ArrayList; +import java.util.List; +import java.util.concurrent.locks.ReentrantLock; + +/** + * TODO: Also flush after minimum size limit is reached? + */ +public class BatchAccumulator<T> implements Closeable { + private final int epoch; + private final Time time; + private final Timer lingerTimer; + private final int lingerMs; + private final int maxBatchSize; + private final CompressionType compressionType; + private final MemoryPool memoryPool; + private final ReentrantLock lock; + private final RecordSerde<T> serde; + + private long nextOffset; + private BatchBuilder<T> currentBatch; + private List<CompletedBatch<T>> completed; + + public BatchAccumulator( + int epoch, + long baseOffset, + int lingerMs, + int maxBatchSize, + MemoryPool memoryPool, + Time time, + CompressionType compressionType, + RecordSerde<T> serde + ) { + this.epoch = epoch; + this.lingerMs = lingerMs; + this.maxBatchSize = maxBatchSize; + this.memoryPool = memoryPool; + this.time = time; + this.lingerTimer = time.timer(lingerMs); + this.compressionType = compressionType; + this.serde = serde; + this.nextOffset = baseOffset; + this.completed = new ArrayList<>(); + this.lock = new ReentrantLock(); + } + + /** + * Append a list of records into an atomic batch. We guarantee all records + * are included in the same underlying record batch so that either all of + * the records become committed or none of them do. + * + * @param epoch the expected leader epoch + * @param records the list of records to include in a batch + * @return the offset of the last message or {@link Long#MAX_VALUE} if the epoch + * does not match + */ + public Long append(int epoch, List<T> records) { + if (epoch != this.epoch) { + // If the epoch does not match, then the state machine probably + // has not gotten the notification about the latest epoch change. + // In this case, ignore the append and return a large offset value + // which will never be committed. + return Long.MAX_VALUE; + } + + Object serdeContext = serde.newWriteContext(); + int batchSize = 0; + for (T record : records) { + batchSize += serde.recordSize(record, serdeContext); + } + + if (batchSize > maxBatchSize) { + throw new IllegalArgumentException("The total size of " + records + " is " + batchSize + + ", which exceeds the maximum allowed batch size of " + maxBatchSize); + } + + lock.lock(); + try { + BatchBuilder<T> batch = maybeAllocateBatch(batchSize); + if (batch == null) { + return null; + } + + if (isEmpty()) { + lingerTimer.update(); + lingerTimer.reset(lingerMs); + } + + for (T record : records) { + batch.appendRecord(record, serdeContext); + nextOffset += 1; + } + + return nextOffset - 1; + } finally { + lock.unlock(); + } + } + + private BatchBuilder<T> maybeAllocateBatch(int batchSize) { + if (currentBatch == null) { + startNewBatch(); + } else if (!currentBatch.hasRoomFor(batchSize)) { + completeCurrentBatch(); + } + return currentBatch; + } + + private void completeCurrentBatch() { + MemoryRecords data = currentBatch.build(); + completed.add(new CompletedBatch<>( + currentBatch.baseOffset(), + currentBatch.records(), + data, + memoryPool, + currentBatch.initialBuffer() + )); + currentBatch = null; + startNewBatch(); + } + + private void startNewBatch() { + ByteBuffer buffer = memoryPool.tryAllocate(maxBatchSize); + if (buffer != null) { + currentBatch = new BatchBuilder<>( + buffer, + serde, + compressionType, + nextOffset, + time.milliseconds(), + false, + RecordBatch.NO_PARTITION_LEADER_EPOCH, + maxBatchSize + ); + } + } + + /** + * Check whether there are any batches which need flushing now. + * + * @param currentTimeMs current time in milliseconds + * @return true if there are batches ready to flush, false otherwise + */ + public boolean needsFlush(long currentTimeMs) { + return timeUntilFlush(currentTimeMs) <= 0; + } + + /** + * Check the time remaining until the next needed flush. If the accumulator + * is empty, then {@link Long#MAX_VALUE} will be returned. + * + * @param currentTimeMs current time in milliseconds + * @return the delay in milliseconds before the next expected flush + */ + public long timeUntilFlush(long currentTimeMs) { + lock.lock(); + try { + lingerTimer.update(currentTimeMs); + if (isEmpty()) { + return Long.MAX_VALUE; + } else { + return lingerTimer.remainingMs(); + } + } finally { + lock.unlock(); + } + } + + private boolean isEmpty() { + lock.lock(); + try { + if (currentBatch != null && currentBatch.nonEmpty()) { + return false; + } else { + return completed.isEmpty(); + } + } finally { + lock.unlock(); + } + } + + /** + * Get the leader epoch, which is constant for each instance. + * + * @return the leader epoch + */ + public int epoch() { + return epoch; + } + + /** + * Flush completed batches. The caller is expected to first check whether + * a flush is expected using {@link #needsFlush(long)} in order to avoid + * unnecessary flushing. + * + * @return the list of completed batches + */ + public List<CompletedBatch<T>> flush() { + lock.lock(); + try { + if (currentBatch != null && currentBatch.nonEmpty()) { + completeCurrentBatch(); + } + + List<CompletedBatch<T>> res = completed; + this.completed = new ArrayList<>(); + return res; + } finally { + lock.unlock(); + } + } + + /** + * Get the number of batches including the one that is currently being + * written to (if it exists). + * + * @return + */ + public int count() { Review comment: I am not sure. We don't have a metric yet, so I thought we might as well start with a thread-safe implementation. If we add a metric in the future, we can probably use an `AtomicInteger` or something and eliminate the locking. ---------------------------------------------------------------- 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. For queries about this service, please contact Infrastructure at: us...@infra.apache.org
