/*
* 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.IOException;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import java.util.NoSuchElementException;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.apache.flink.api.common.typeutils.TypeSerializer;
import org.apache.flink.core.memory.DataInputView;
import org.apache.flink.core.memory.MemorySegment;
import org.apache.flink.runtime.io.disk.SpillingBuffer;
import org.apache.flink.runtime.io.disk.iomanager.IOManager;
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.ResettableIterator;
/**
* Implementation of a resettable iterator. While iterating the first time over the data, the iterator writes the
* records to a spillable buffer. Any subsequent iteration re-reads the data from that buffer.
*
* @param <T> The type of record that the iterator handles.
*/
public class SpillingResettableIterator<T> implements ResettableIterator<T> {
private static final Logger LOG = LoggerFactory.getLogger(SpillingResettableIterator.class);
// ------------------------------------------------------------------------
private T next;
private T instance;
protected DataInputView inView;
protected final TypeSerializer<T> serializer;
private int elementCount;
private int currentElementNum;
protected final SpillingBuffer buffer;
protected final Iterator<T> input;
protected final MemoryManager memoryManager;
private final List<MemorySegment> memorySegments;
private final boolean releaseMemoryOnClose;
// ------------------------------------------------------------------------
public SpillingResettableIterator(Iterator<T> input, TypeSerializer<T> serializer,
MemoryManager memoryManager, IOManager ioManager,
int numPages, AbstractInvokable parentTask)
throws MemoryAllocationException
{
this(input, serializer, memoryManager, ioManager, memoryManager.allocatePages(parentTask, numPages), true);
}
public SpillingResettableIterator(Iterator<T> input, TypeSerializer<T> serializer,
MemoryManager memoryManager, IOManager ioManager, List<MemorySegment> memory)
{
this(input, serializer, memoryManager, ioManager, memory, false);
}
private SpillingResettableIterator(Iterator<T> input, TypeSerializer<T> serializer,
MemoryManager memoryManager, IOManager ioManager,
List<MemorySegment> memory, boolean releaseMemOnClose)
{
this.memoryManager = memoryManager;
this.input = input;
this.instance = serializer.createInstance();
this.serializer = serializer;
this.memorySegments = memory;
this.releaseMemoryOnClose = releaseMemOnClose;
if (LOG.isDebugEnabled()) {
LOG.debug("Creating spilling resettable iterator with " + memory.size() + " pages of memory.");
}
this.buffer = new SpillingBuffer(ioManager, new ListMemorySegmentSource(memory), memoryManager.getPageSize());
}
public void open() {
if (LOG.isDebugEnabled()) {
LOG.debug("Spilling Resettable Iterator opened.");
}
}
public void reset() throws IOException {
this.inView = this.buffer.flip();
this.currentElementNum = 0;
}
@Override
public boolean hasNext() {
if (this.next == null) {
if (this.inView != null) {
if (this.currentElementNum < this.elementCount) {
try {
this.instance = this.serializer.deserialize(this.instance, this.inView);
} catch (IOException e) {
throw new RuntimeException("SpillingIterator: Error reading element from buffer.", e);
}
this.next = this.instance;
this.currentElementNum++;
return true;
} else {
return false;
}
} else {
// writing pass (first)
if (this.input.hasNext()) {
this.next = this.input.next();
try {
this.serializer.serialize(this.next, this.buffer);
} catch (IOException e) {
throw new RuntimeException("SpillingIterator: Error writing element to buffer.", e);
}
this.elementCount++;
return true;
} else {
return false;
}
}
} else {
return true;
}
}
@Override
public T next() {
if (this.next != null || hasNext()) {
final T out = this.next;
this.next = null;
return out;
} else {
throw new NoSuchElementException();
}
}
@Override
public void remove() {
throw new UnsupportedOperationException();
}
public List<MemorySegment> close() throws IOException {
if (LOG.isDebugEnabled()) {
LOG.debug("Spilling Resettable Iterator closing. Stored " + this.elementCount + " records.");
}
this.inView = null;
final List<MemorySegment> memory = this.buffer.close();
memory.addAll(this.memorySegments);
this.memorySegments.clear();
if (this.releaseMemoryOnClose) {
this.memoryManager.release(memory);
return Collections.emptyList();
} else {
return memory;
}
}
}