HADOOP-17774. S3A bytesRead FS statistic showing twice the correct value (#3144)

Contributed by: Mehakmeet Singh

hadoop-tools/hadoop-aws/src/main/java/org/apache/hadoop/fs/s3a/S3AFileSystem.java

@@ -712,6 +712,16 @@ public class S3AFileSystem extends FileSystem implements StreamCapabilities,
     return instrumentation;
   }
 
+  /**
+   * Get FS Statistic for this S3AFS instance.
+   *
+   * @return FS statistic instance.
+   */
+  @VisibleForTesting
+  public FileSystem.Statistics getFsStatistics() {
+    return statistics;
+  }
+
   /**
    * Get current listing instance.
    * @return this instance's listing.

hadoop-tools/hadoop-aws/src/main/java/org/apache/hadoop/fs/s3a/S3AInstrumentation.java

@@ -988,6 +988,7 @@ public class S3AInstrumentation implements Closeable, MetricsSource,
         closed.incrementAndGet();
         bytesDiscardedInClose.addAndGet(remainingInCurrentRequest);
         totalBytesRead.addAndGet(remainingInCurrentRequest);
+        filesystemStatistics.incrementBytesRead(remainingInCurrentRequest);
       }
     }
 
@@ -1144,7 +1145,6 @@ public class S3AInstrumentation implements Closeable, MetricsSource,
         // increment the filesystem statistics for this thread.
         if (filesystemStatistics != null) {
           long t = getTotalBytesRead();
-          filesystemStatistics.incrementBytesRead(t);
           filesystemStatistics.incrementBytesReadByDistance(DISTANCE, t);
         }
       }

hadoop-tools/hadoop-aws/src/test/java/org/apache/hadoop/fs/s3a/statistics/ITestS3AFileSystemStatistic.java

@@ -0,0 +1,75 @@
+/*
+ * 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.hadoop.fs.s3a.statistics;
+
+import java.io.IOException;
+
+import org.junit.Test;
+
+import org.apache.hadoop.fs.FSDataInputStream;
+import org.apache.hadoop.fs.FSDataOutputStream;
+import org.apache.hadoop.fs.FileSystem;
+import org.apache.hadoop.fs.Path;
+import org.apache.hadoop.fs.s3a.AbstractS3ATestBase;
+import org.apache.hadoop.fs.s3a.S3AFileSystem;
+import org.apache.hadoop.fs.statistics.IOStatisticAssertions;
+import org.apache.hadoop.fs.statistics.StreamStatisticNames;
+
+public class ITestS3AFileSystemStatistic extends AbstractS3ATestBase {
+
+  private static final int ONE_KB = 1024;
+  private static final int TWO_KB = 2 * ONE_KB;
+
+  /**
+   * Verify the fs statistic bytesRead after reading from 2 different
+   * InputStreams for the same filesystem instance.
+   */
+  @Test
+  public void testBytesReadWithStream() throws IOException {
+    S3AFileSystem fs = getFileSystem();
+    Path filePath = path(getMethodName());
+    byte[] oneKbBuf = new byte[ONE_KB];
+
+    // Writing 1KB in a file.
+    try (FSDataOutputStream out = fs.create(filePath)) {
+      out.write(oneKbBuf);
+      // Verify if correct number of bytes were written.
+      IOStatisticAssertions.assertThatStatisticCounter(out.getIOStatistics(),
+          StreamStatisticNames.STREAM_WRITE_BYTES)
+          .describedAs("Bytes written by OutputStream "
+              + "should match the actual bytes")
+          .isEqualTo(ONE_KB);
+    }
+
+    // Reading 1KB from first InputStream.
+    try (FSDataInputStream in = fs.open(filePath, ONE_KB)) {
+      in.readFully(0, oneKbBuf);
+    }
+
+    // Reading 1KB from second InputStream.
+    try (FSDataInputStream in2 = fs.open(filePath, ONE_KB)) {
+      in2.readFully(0, oneKbBuf);
+    }
+
+    FileSystem.Statistics fsStats = fs.getFsStatistics();
+    // Verifying that total bytes read by FS is equal to 2KB.
+    assertEquals("Mismatch in number of FS bytes read by InputStreams", TWO_KB,
+        fsStats.getBytesRead());
+  }
+}