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https://issues.apache.org/jira/browse/HADOOP-19613?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18009146#comment-18009146
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ASF GitHub Bot commented on HADOOP-19613:
-----------------------------------------
manika137 commented on code in PR #7801:
URL: https://github.com/apache/hadoop/pull/7801#discussion_r2224553438
##########
hadoop-tools/hadoop-azure/src/main/java/org/apache/hadoop/fs/azurebfs/services/ReadBufferManagerV1.java:
##########
@@ -0,0 +1,612 @@
+/**
+ * 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
+ * <p>
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * <p>
+ * 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.hadoop.fs.azurebfs.services;
+
+import org.apache.hadoop.fs.azurebfs.contracts.services.ReadBufferStatus;
+
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.Iterator;
+import java.util.LinkedList;
+import java.util.concurrent.CountDownLatch;
+
+import org.apache.hadoop.fs.azurebfs.utils.TracingContext;
+import org.apache.hadoop.classification.VisibleForTesting;
+
+/**
+ * The Read Buffer Manager for Rest AbfsClient.
+ * V1 implementation of ReadBufferManager.
+ */
+final class ReadBufferManagerV1 extends ReadBufferManager {
+
+ private static final int NUM_BUFFERS = 16;
+ private static final int NUM_THREADS = 8;
+ private static final int DEFAULT_THRESHOLD_AGE_MILLISECONDS = 3000;
+
+ private Thread[] threads = new Thread[NUM_THREADS];
+ private byte[][] buffers;
+ private static ReadBufferManagerV1 bufferManager;
+
+ // hide instance constructor
+ private ReadBufferManagerV1() {
+ LOGGER.trace("Creating readbuffer manager with HADOOP-18546 patch");
+ }
+
+ /**
+ * Sets the read buffer manager configurations.
+ * @param readAheadBlockSize the size of the read-ahead block in bytes
+ */
+ static void setReadBufferManagerConfigs(int readAheadBlockSize) {
+ if (bufferManager == null) {
+ LOGGER.debug(
+ "ReadBufferManagerV1 not initialized yet. Overriding
readAheadBlockSize as {}",
+ readAheadBlockSize);
+ setReadAheadBlockSize(readAheadBlockSize);
+ setThresholdAgeMilliseconds(DEFAULT_THRESHOLD_AGE_MILLISECONDS);
+ }
+ }
+
+ /**
+ * Returns the singleton instance of ReadBufferManagerV1.
+ * @return the singleton instance of ReadBufferManagerV1
+ */
+ static ReadBufferManagerV1 getBufferManager() {
+ if (bufferManager == null) {
+ LOCK.lock();
+ try {
+ if (bufferManager == null) {
+ bufferManager = new ReadBufferManagerV1();
+ bufferManager.init();
+ }
+ } finally {
+ LOCK.unlock();
+ }
+ }
+ return bufferManager;
+ }
+
+ /**
+ * {@inheritDoc}
+ */
+ @Override
+ void init() {
+ buffers = new byte[NUM_BUFFERS][];
+ for (int i = 0; i < NUM_BUFFERS; i++) {
+ buffers[i] = new byte[getReadAheadBlockSize()]; // same buffers are
reused. The byte array never goes back to GC
+ getFreeList().add(i);
+ }
+ for (int i = 0; i < NUM_THREADS; i++) {
+ Thread t = new Thread(new ReadBufferWorker(i, this));
+ t.setDaemon(true);
+ threads[i] = t;
+ t.setName("ABFS-prefetch-" + i);
+ t.start();
+ }
+ ReadBufferWorker.UNLEASH_WORKERS.countDown();
+ }
+
+ /**
+ * {@inheritDoc}
+ */
+ @Override
+ public void queueReadAhead(final AbfsInputStream stream, final long
requestedOffset, final int requestedLength,
+ TracingContext tracingContext) {
+ if (LOGGER.isTraceEnabled()) {
Review Comment:
does anything happen if we skip the if condition and use LOG.trace()
directly?
> ABFS: [ReadAheadV2] Refactor ReadBufferManager to isolate new code with the
> current working code
> ------------------------------------------------------------------------------------------------
>
> Key: HADOOP-19613
> URL: https://issues.apache.org/jira/browse/HADOOP-19613
> Project: Hadoop Common
> Issue Type: Sub-task
> Components: fs/azure
> Affects Versions: 3.5.0, 3.4.1
> Reporter: Anuj Modi
> Assignee: Anuj Modi
> Priority: Major
> Labels: pull-request-available
>
> Read Buffer Manager used today was introduced way back and has been stable
> for quite a while.
> Read Buffer Manager to be introduced as part of
> https://issues.apache.org/jira/browse/HADOOP-19596 will introduce many
> changes incrementally over time. While the development goes on and we are
> able to fully stabilise the optimized version we need the current flow to be
> functional and undisturbed.
> This work item is to isolate that from new code by refactoring
> ReadBufferManager class to have 2 different implementations with same public
> interfaces: ReadBufferManagerV1 and ReadBufferManagerV2.
> This will also introduce new configs that can be used to toggle between new
> and old code.
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