kafka BufferSupplier 源码
kafka BufferSupplier 代码
文件路径:/clients/src/main/java/org/apache/kafka/common/utils/BufferSupplier.java
/*
* 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.common.utils;
import java.nio.ByteBuffer;
import java.util.ArrayDeque;
import java.util.Deque;
import java.util.HashMap;
import java.util.Map;
/**
* Simple non-threadsafe interface for caching byte buffers. This is suitable for simple cases like ensuring that
* a given KafkaConsumer reuses the same decompression buffer when iterating over fetched records. For small record
* batches, allocating a potentially large buffer (64 KB for LZ4) will dominate the cost of decompressing and
* iterating over the records in the batch.
*/
public abstract class BufferSupplier implements AutoCloseable {
public static final BufferSupplier NO_CACHING = new BufferSupplier() {
@Override
public ByteBuffer get(int capacity) {
return ByteBuffer.allocate(capacity);
}
@Override
public void release(ByteBuffer buffer) {}
@Override
public void close() {}
};
public static BufferSupplier create() {
return new DefaultSupplier();
}
/**
* Supply a buffer with the required capacity. This may return a cached buffer or allocate a new instance.
*/
public abstract ByteBuffer get(int capacity);
/**
* Return the provided buffer to be reused by a subsequent call to `get`.
*/
public abstract void release(ByteBuffer buffer);
/**
* Release all resources associated with this supplier.
*/
public abstract void close();
private static class DefaultSupplier extends BufferSupplier {
// We currently use a single block size, so optimise for that case
private final Map<Integer, Deque<ByteBuffer>> bufferMap = new HashMap<>(1);
@Override
public ByteBuffer get(int size) {
Deque<ByteBuffer> bufferQueue = bufferMap.get(size);
if (bufferQueue == null || bufferQueue.isEmpty())
return ByteBuffer.allocate(size);
else
return bufferQueue.pollFirst();
}
@Override
public void release(ByteBuffer buffer) {
buffer.clear();
Deque<ByteBuffer> bufferQueue = bufferMap.get(buffer.capacity());
if (bufferQueue == null) {
// We currently keep a single buffer in flight, so optimise for that case
bufferQueue = new ArrayDeque<>(1);
bufferMap.put(buffer.capacity(), bufferQueue);
}
bufferQueue.addLast(buffer);
}
@Override
public void close() {
bufferMap.clear();
}
}
/**
* Simple buffer supplier for single-threaded usage. It caches a single buffer, which grows
* monotonically as needed to fulfill the allocation request.
*/
public static class GrowableBufferSupplier extends BufferSupplier {
private ByteBuffer cachedBuffer;
@Override
public ByteBuffer get(int minCapacity) {
if (cachedBuffer != null && cachedBuffer.capacity() >= minCapacity) {
ByteBuffer res = cachedBuffer;
cachedBuffer = null;
return res;
} else {
cachedBuffer = null;
return ByteBuffer.allocate(minCapacity);
}
}
@Override
public void release(ByteBuffer buffer) {
buffer.clear();
cachedBuffer = buffer;
}
@Override
public void close() {
cachedBuffer = null;
}
}
}
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