/*
* 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.flink.runtime.operators.resettable;
import java.io.EOFException;
import java.io.IOException;
import java.util.ArrayList;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.apache.flink.api.common.typeutils.TypeSerializer;
import org.apache.flink.core.memory.MemorySegment;
import org.apache.flink.runtime.io.disk.RandomAccessInputView;
import org.apache.flink.runtime.io.disk.SimpleCollectingOutputView;
import org.apache.flink.runtime.jobgraph.tasks.AbstractInvokable;
import org.apache.flink.runtime.memorymanager.ListMemorySegmentSource;
import org.apache.flink.runtime.memorymanager.MemoryAllocationException;
import org.apache.flink.runtime.memorymanager.MemoryManager;
import org.apache.flink.runtime.util.MemoryBlockIterator;
/**
* Base class for iterators that fetch a block of data into main memory and offer resettable
* access to the data in that block.
*/
abstract class AbstractBlockResettableIterator<T> implements MemoryBlockIterator {
protected static final Logger LOG = LoggerFactory.getLogger(AbstractBlockResettableIterator.class);
// ------------------------------------------------------------------------
protected final RandomAccessInputView readView;
protected final SimpleCollectingOutputView collectingView;
protected final TypeSerializer<T> serializer;
protected int numRecordsInBuffer;
protected int numRecordsReturned;
protected final ArrayList<MemorySegment> emptySegments;
protected final ArrayList<MemorySegment> fullSegments;
private final MemoryManager memoryManager;
protected volatile boolean closed; // volatile since it may be asynchronously set to abort after current block
// ------------------------------------------------------------------------
protected AbstractBlockResettableIterator(TypeSerializer<T> serializer, MemoryManager memoryManager,
int numPages, AbstractInvokable ownerTask)
throws MemoryAllocationException
{
if (numPages < 1) {
throw new IllegalArgumentException("Block Resettable iterator requires at leat one page of memory");
}
this.memoryManager = memoryManager;
this.serializer = serializer;
this.emptySegments = new ArrayList<MemorySegment>(numPages);
this.fullSegments = new ArrayList<MemorySegment>(numPages);
memoryManager.allocatePages(ownerTask, emptySegments, numPages);
this.collectingView = new SimpleCollectingOutputView(this.fullSegments,
new ListMemorySegmentSource(this.emptySegments), memoryManager.getPageSize());
this.readView = new RandomAccessInputView(this.fullSegments, memoryManager.getPageSize());
if (LOG.isDebugEnabled()) {
LOG.debug("Iterator initialized using " + numPages + " memory buffers.");
}
}
// --------------------------------------------------------------------------------------------
public void open() {
if (LOG.isDebugEnabled()) {
LOG.debug("Block Resettable Iterator opened.");
}
}
public void reset() {
if (this.closed) {
throw new IllegalStateException("Iterator was closed.");
}
this.readView.setReadPosition(0);
this.numRecordsReturned = 0;
}
@Override
public boolean nextBlock() throws IOException {
this.numRecordsInBuffer = 0;
// add the full segments to the empty ones
for (int i = this.fullSegments.size() - 1; i >= 0; i--) {
this.emptySegments.add(this.fullSegments.remove(i));
}
// reset the views
this.collectingView.reset();
this.readView.setReadPosition(0);
return true;
}
/**
* This method closes the iterator and releases all resources. This method works both as a regular
* shutdown and as a canceling method. The method may be called multiple times and will not produce
* an error.
*/
public void close() {
synchronized (this) {
if (this.closed) {
return;
}
this.closed = true;
}
this.numRecordsInBuffer = 0;
this.numRecordsReturned = 0;
// add the full segments to the empty ones
for (int i = this.fullSegments.size() - 1; i >= 0; i--) {
this.emptySegments.add(this.fullSegments.remove(i));
}
// release the memory segment
this.memoryManager.release(this.emptySegments);
this.emptySegments.clear();
if (LOG.isDebugEnabled()) {
LOG.debug("Block Resettable Iterator closed.");
}
}
// --------------------------------------------------------------------------------------------
protected boolean writeNextRecord(T record) throws IOException {
try {
this.serializer.serialize(record, this.collectingView);
this.numRecordsInBuffer++;
return true;
} catch (EOFException eofex) {
return false;
}
}
protected T getNextRecord(T reuse) throws IOException {
if (this.numRecordsReturned < this.numRecordsInBuffer) {
this.numRecordsReturned++;
return this.serializer.deserialize(reuse, this.readView);
} else {
return null;
}
}
}