[
https://issues.apache.org/jira/browse/PARQUET-2149?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17539119#comment-17539119
]
ASF GitHub Bot commented on PARQUET-2149:
-----------------------------------------
parthchandra commented on code in PR #968:
URL: https://github.com/apache/parquet-mr/pull/968#discussion_r876197602
##########
parquet-column/src/main/java/org/apache/parquet/column/page/PageReader.java:
##########
@@ -37,4 +39,9 @@ public interface PageReader {
* @return the next page in that chunk or null if after the last page
*/
DataPage readPage();
+
+ /**
+ * Close the page reader. By default it is no-op.
+ */
+ default void close() throws IOException {}
Review Comment:
Sure.
##########
parquet-common/src/main/java/org/apache/parquet/bytes/AsyncMultiBufferInputStream.java:
##########
@@ -0,0 +1,173 @@
+/*
+ * 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.parquet.bytes;
+
+import java.io.IOException;
+import java.nio.ByteBuffer;
+import java.util.List;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Future;
+import java.util.concurrent.LinkedBlockingQueue;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.LongAccumulator;
+import java.util.concurrent.atomic.LongAdder;
+import org.apache.parquet.io.SeekableInputStream;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+class AsyncMultiBufferInputStream extends MultiBufferInputStream {
+
+ private static final Logger LOG =
LoggerFactory.getLogger(AsyncMultiBufferInputStream.class);
+
+ final SeekableInputStream fileInputStream;
+ int fetchIndex = 0;
+ int readIndex = 0;
+ ExecutorService threadPool;
+ LinkedBlockingQueue<Future<Void>> readFutures;
+ boolean closed = false;
+ Exception ioException;
+
+ LongAdder totalTimeBlocked = new LongAdder();
+ LongAdder totalCountBlocked = new LongAdder();
+ LongAccumulator maxTimeBlocked = new LongAccumulator(Long::max, 0L);
+
+ AsyncMultiBufferInputStream(ExecutorService threadPool, SeekableInputStream
fileInputStream,
+ List<ByteBuffer> buffers) {
+ super(buffers);
+ this.fileInputStream = fileInputStream;
+ this.threadPool = threadPool;
+ readFutures = new LinkedBlockingQueue<>(buffers.size());
+ if (LOG.isDebugEnabled()) {
+ LOG.debug("ASYNC: Begin read into buffers ");
+ for (ByteBuffer buf : buffers) {
+ LOG.debug("ASYNC: buffer {} ", buf);
+ }
+ }
+ fetchAll();
+ }
+
+ private void checkState() {
+ if (closed) {
+ throw new RuntimeException("Stream is closed");
+ }
+ synchronized (this) {
+ if (ioException != null) {
+ throw new RuntimeException(ioException);
+ }
+ }
+ }
+
+ private void fetchAll() {
+ checkState();
+ submitReadTask(0);
+ }
+
+ private void submitReadTask(int bufferNo) {
+ ByteBuffer buffer = buffers.get(bufferNo);
+ try {
+ readFutures.put(threadPool.submit(() -> {
+ readOneBuffer(buffer);
+ if (bufferNo < buffers.size() - 1) {
+ submitReadTask(bufferNo + 1);
+ }
+ return null;
+ })
+ );
+ } catch (InterruptedException e) {
+ Thread.currentThread().interrupt();
+ throw new RuntimeException(e);
+ }
+ }
+
+ private void readOneBuffer(ByteBuffer buffer) {
+ long startTime = System.nanoTime();
+ try {
+ fileInputStream.readFully(buffer);
+ buffer.flip();
+ long readCompleted = System.nanoTime();
+ long timeSpent = readCompleted - startTime;
+ LOG.debug("ASYNC Stream: READ - {}", timeSpent / 1000.0);
+ long putStart = System.nanoTime();
+ long putCompleted = System.nanoTime();
+ LOG.debug("ASYNC Stream: FS READ (output) BLOCKED - {}",
+ (putCompleted - putStart) / 1000.0);
+ fetchIndex++;
+ } catch (IOException e) {
+ // Save the exception so that the calling thread can check if something
went wrong.
+ // checkState will throw an exception if the read task has failed.
+ synchronized(this) {
+ ioException = e;
+ }
+ throw new RuntimeException(e);
+ }
+ }
+
+ @Override
+ public boolean nextBuffer() {
+ checkState();
+ // hack: parent constructor can call this method before this class is
fully initialized.
+ // Just return without doing anything.
+ if (readFutures == null) {
+ return false;
+ }
Review Comment:
Glad you made me look. The synchronization was needed because I was saving
any exception that might have occurred in the reader thread. However, that
exception will be captured by the Future object and thrown as an
ExecutionException when `Future,get` is called in line 135.
So we don't really need to save the exception and the synchronization around
it can also be removed.
> Implement async IO for Parquet file reader
> ------------------------------------------
>
> Key: PARQUET-2149
> URL: https://issues.apache.org/jira/browse/PARQUET-2149
> Project: Parquet
> Issue Type: Improvement
> Components: parquet-mr
> Reporter: Parth Chandra
> Priority: Major
>
> ParquetFileReader's implementation has the following flow (simplified) -
> - For every column -> Read from storage in 8MB blocks -> Read all
> uncompressed pages into output queue
> - From output queues -> (downstream ) decompression + decoding
> This flow is serialized, which means that downstream threads are blocked
> until the data has been read. Because a large part of the time spent is
> waiting for data from storage, threads are idle and CPU utilization is really
> low.
> There is no reason why this cannot be made asynchronous _and_ parallel. So
> For Column _i_ -> reading one chunk until end, from storage -> intermediate
> output queue -> read one uncompressed page until end -> output queue ->
> (downstream ) decompression + decoding
> Note that this can be made completely self contained in ParquetFileReader and
> downstream implementations like Iceberg and Spark will automatically be able
> to take advantage without code change as long as the ParquetFileReader apis
> are not changed.
> In past work with async io [Drill - async page reader
> |https://github.com/apache/drill/blob/master/exec/java-exec/src/main/java/org/apache/drill/exec/store/parquet/columnreaders/AsyncPageReader.java]
> , I have seen 2x-3x improvement in reading speed for Parquet files.
--
This message was sent by Atlassian Jira
(v8.20.7#820007)
