kafka MemoryPool 源码
kafka MemoryPool 代码
文件路径：/clients/src/main/java/org/apache/kafka/common/memory/MemoryPool.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.memory;
import java.nio.ByteBuffer;
/**
* A common memory pool interface for non-blocking pools.
* Every buffer returned from {@link #tryAllocate(int)} must always be {@link #release(ByteBuffer) released}.
*/
public interface MemoryPool {
MemoryPool NONE = new MemoryPool() {
@Override
public ByteBuffer tryAllocate(int sizeBytes) {
return ByteBuffer.allocate(sizeBytes);
}
@Override
public void release(ByteBuffer previouslyAllocated) {
//nop
}
@Override
public long size() {
return Long.MAX_VALUE;
}
@Override
public long availableMemory() {
return Long.MAX_VALUE;
}
@Override
public boolean isOutOfMemory() {
return false;
}
@Override
public String toString() {
return "NONE";
}
};
/**
* Tries to acquire a ByteBuffer of the specified size
* @param sizeBytes size required
* @return a ByteBuffer (which later needs to be release()ed), or null if no memory available.
* the buffer will be of the exact size requested, even if backed by a larger chunk of memory
*/
ByteBuffer tryAllocate(int sizeBytes);
/**
* Returns a previously allocated buffer to the pool.
* @param previouslyAllocated a buffer previously returned from tryAllocate()
*/
void release(ByteBuffer previouslyAllocated);
/**
* Returns the total size of this pool
* @return total size, in bytes
*/
long size();
/**
* Returns the amount of memory available for allocation by this pool.
* NOTE: result may be negative (pools may over allocate to avoid starvation issues)
* @return bytes available
*/
long availableMemory();
/**
* Returns true if the pool cannot currently allocate any more buffers
* - meaning total outstanding buffers meets or exceeds pool size and
* some would need to be released before further allocations are possible.
*
* This is equivalent to availableMemory() <= 0
* @return true if out of memory
*/
boolean isOutOfMemory();
}
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