HADOOP-19354. S3AInputStream to be created by factory under S3AStore.

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

@@ -1560,6 +1560,11 @@ private Constants() {
    */
   public static final String AWS_AUTH_CLASS_PREFIX = "com.amazonaws.auth";
 
+
+  public static final String INPUT_STREAM_TYPE = "fs.s3a.input.stream.type";
+
+  public static final String INPUT_STREAM_TYPE_DEFAULT = "classic";
+
   /**
    * Controls whether the prefetching input stream is enabled.
    */

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

@@ -0,0 +1,29 @@
+package org.apache.hadoop.fs.s3a;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public enum InputStreamType {
+  CLASSIC("classic"),
+  PREFETCH("prefetch"),
+  ANALYTICS("analytics");
+
+  private final String name;
+
+  private static final Logger LOG = LoggerFactory.getLogger(InputStreamType.class);
+
+  InputStreamType(String name) {
+    this.name = name;
+  }
+
+  public static InputStreamType fromString(String inputStreamType) {
+    for (InputStreamType value : values()) {
+      if (value.name.equalsIgnoreCase(inputStreamType)) {
+        return value;
+      }
+    }
+    LOG.warn("Unknown input stream type {}, using default classic stream.", inputStreamType);
+
+    return CLASSIC;
+  }
+}