HADOOP-11867. Add a high-performance vectored read API. (#3904)

part of HADOOP-18103. 
Add support for multiple ranged vectored read api in PositionedReadable.
The default iterates through the ranges to read each synchronously,
but the intent is that FSDataInputStream subclasses can make more
efficient readers especially in object stores implementation.

Also added implementation in S3A where smaller ranges are merged and 
sliced byte buffers are returned to the readers. All the merged ranged are 
fetched from S3 asynchronously.


Contributed By: Owen O'Malley and Mukund Thakur

Author: mukund-thakur

dev-support/Jenkinsfile

@@ -47,7 +47,7 @@ pipeline {
 
     options {
         buildDiscarder(logRotator(numToKeepStr: '5'))
-        timeout (time: 24, unit: 'HOURS')
+        timeout (time: 48, unit: 'HOURS')
         timestamps()
         checkoutToSubdirectory('src')
     }

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/BufferedFSInputStream.java

@@ -1,4 +1,4 @@
-/**
+/*
  * 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
@@ -22,6 +22,9 @@
 import java.io.FileDescriptor;
 import java.io.IOException;
 import java.util.StringJoiner;
+import java.nio.ByteBuffer;
+import java.util.List;
+import java.util.function.IntFunction;
 
 import org.apache.hadoop.classification.InterfaceAudience;
 import org.apache.hadoop.classification.InterfaceStability;
@@ -158,8 +161,24 @@ public IOStatistics getIOStatistics() {
   @Override
   public String toString() {
     return new StringJoiner(", ",
-        BufferedFSInputStream.class.getSimpleName() + "[", "]")
-        .add("in=" + in)
-        .toString();
+            BufferedFSInputStream.class.getSimpleName() + "[", "]")
+            .add("in=" + in)
+            .toString();
+  }
+
+  @Override
+  public int minSeekForVectorReads() {
+    return ((PositionedReadable) in).minSeekForVectorReads();
+  }
+
+  @Override
+  public int maxReadSizeForVectorReads() {
+    return ((PositionedReadable) in).maxReadSizeForVectorReads();
+  }
+
+  @Override
+  public void readVectored(List<? extends FileRange> ranges,
+                           IntFunction<ByteBuffer> allocate) throws IOException {
+    ((PositionedReadable) in).readVectored(ranges, allocate);
   }
 }