kafka SimpleMemoryPool 源码
kafka SimpleMemoryPool 代码
文件路径:/clients/src/main/java/org/apache/kafka/common/memory/SimpleMemoryPool.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;
import java.util.concurrent.atomic.AtomicLong;
import org.apache.kafka.common.metrics.Sensor;
import org.apache.kafka.common.utils.Utils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* a simple pool implementation. this implementation just provides a limit on the total outstanding memory.
* any buffer allocated must be release()ed always otherwise memory is not marked as reclaimed (and "leak"s)
*/
public class SimpleMemoryPool implements MemoryPool {
protected final Logger log = LoggerFactory.getLogger(getClass()); //subclass-friendly
protected final long sizeBytes;
protected final boolean strict;
protected final AtomicLong availableMemory;
protected final int maxSingleAllocationSize;
protected final AtomicLong startOfNoMemPeriod = new AtomicLong(); //nanoseconds
protected volatile Sensor oomTimeSensor;
public SimpleMemoryPool(long sizeInBytes, int maxSingleAllocationBytes, boolean strict, Sensor oomPeriodSensor) {
if (sizeInBytes <= 0 || maxSingleAllocationBytes <= 0 || maxSingleAllocationBytes > sizeInBytes)
throw new IllegalArgumentException("must provide a positive size and max single allocation size smaller than size."
+ "provided " + sizeInBytes + " and " + maxSingleAllocationBytes + " respectively");
this.sizeBytes = sizeInBytes;
this.strict = strict;
this.availableMemory = new AtomicLong(sizeInBytes);
this.maxSingleAllocationSize = maxSingleAllocationBytes;
this.oomTimeSensor = oomPeriodSensor;
}
@Override
public ByteBuffer tryAllocate(int sizeBytes) {
if (sizeBytes < 1)
throw new IllegalArgumentException("requested size " + sizeBytes + "<=0");
if (sizeBytes > maxSingleAllocationSize)
throw new IllegalArgumentException("requested size " + sizeBytes + " is larger than maxSingleAllocationSize " + maxSingleAllocationSize);
long available;
boolean success = false;
//in strict mode we will only allocate memory if we have at least the size required.
//in non-strict mode we will allocate memory if we have _any_ memory available (so available memory
//can dip into the negative and max allocated memory would be sizeBytes + maxSingleAllocationSize)
long threshold = strict ? sizeBytes : 1;
while ((available = availableMemory.get()) >= threshold) {
success = availableMemory.compareAndSet(available, available - sizeBytes);
if (success)
break;
}
if (success) {
maybeRecordEndOfDrySpell();
} else {
if (oomTimeSensor != null) {
startOfNoMemPeriod.compareAndSet(0, System.nanoTime());
}
log.trace("refused to allocate buffer of size {}", sizeBytes);
return null;
}
ByteBuffer allocated = ByteBuffer.allocate(sizeBytes);
bufferToBeReturned(allocated);
return allocated;
}
@Override
public void release(ByteBuffer previouslyAllocated) {
if (previouslyAllocated == null)
throw new IllegalArgumentException("provided null buffer");
bufferToBeReleased(previouslyAllocated);
availableMemory.addAndGet(previouslyAllocated.capacity());
maybeRecordEndOfDrySpell();
}
@Override
public long size() {
return sizeBytes;
}
@Override
public long availableMemory() {
return availableMemory.get();
}
@Override
public boolean isOutOfMemory() {
return availableMemory.get() <= 0;
}
//allows subclasses to do their own bookkeeping (and validation) _before_ memory is returned to client code.
protected void bufferToBeReturned(ByteBuffer justAllocated) {
log.trace("allocated buffer of size {} ", justAllocated.capacity());
}
//allows subclasses to do their own bookkeeping (and validation) _before_ memory is marked as reclaimed.
protected void bufferToBeReleased(ByteBuffer justReleased) {
log.trace("released buffer of size {}", justReleased.capacity());
}
@Override
public String toString() {
long allocated = sizeBytes - availableMemory.get();
return "SimpleMemoryPool{" + Utils.formatBytes(allocated) + "/" + Utils.formatBytes(sizeBytes) + " used}";
}
protected void maybeRecordEndOfDrySpell() {
if (oomTimeSensor != null) {
long startOfDrySpell = startOfNoMemPeriod.getAndSet(0);
if (startOfDrySpell != 0) {
//how long were we refusing allocation requests for
oomTimeSensor.record((System.nanoTime() - startOfDrySpell) / 1000000.0); //fractional (double) millis
}
}
}
}
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