HADOOP-18517. fs.azure.enable.readahead removed from openFile() options

Removed the fs.azure.enable.readahead option from openFile(); its
a sysadmin option only.

For openFile(), I think we should focus on "policy", rather than explicit
tuning options. e.g "random/vectored" could disable prefetching; sequential
would enable it...

Change-Id: I26d2a75f8c0815bf35a9fa876c94b9cfe7b8dc5c

Author: steveloughran

hadoop-tools/hadoop-azure/src/main/java/org/apache/hadoop/fs/azurebfs/AzureBlobFileSystemStore.java

@@ -806,15 +806,11 @@ private AbfsInputStreamContext populateAbfsInputStreamContext(
         .map(c -> c.getBoolean(FS_AZURE_BUFFERED_PREAD_DISABLE, false))
         .orElse(false);
     // readahead is cluster config unless openfile explicitly sets it.
-    boolean readahead = abfsConfiguration.isReadAheadEnabled();
-    boolean readAheadEnabled = options
-            .map(c -> c.getBoolean(FS_AZURE_ENABLE_READAHEAD, readahead))
-            .orElse(readahead);
     return new AbfsInputStreamContext(abfsConfiguration.getSasTokenRenewPeriodForStreamsInSeconds())
             .withReadBufferSize(abfsConfiguration.getReadBufferSize())
             .withReadAheadQueueDepth(abfsConfiguration.getReadAheadQueueDepth())
             .withTolerateOobAppends(abfsConfiguration.getTolerateOobAppends())
-            .isReadAheadEnabled(readAheadEnabled)
+            .isReadAheadEnabled(abfsConfiguration.isReadAheadEnabled())
             .withReadSmallFilesCompletely(abfsConfiguration.readSmallFilesCompletely())
             .withOptimizeFooterRead(abfsConfiguration.optimizeFooterRead())
             .withReadAheadRange(abfsConfiguration.getReadAheadRange())

hadoop-tools/hadoop-azure/src/main/java/org/apache/hadoop/fs/azurebfs/constants/ConfigurationKeys.java

@@ -188,7 +188,7 @@ public final class ConfigurationKeys {
   public static final String AZURE_KEY_ACCOUNT_SHELLKEYPROVIDER_SCRIPT = "fs.azure.shellkeyprovider.script";
 
   /**
-   * Enable or disable readahead buffer in AbfsInputStream. It is enabled by default.
+   * Enable or disable readahead buffer in AbfsInputStream.
    * Value: {@value}.
    */
   public static final String FS_AZURE_ENABLE_READAHEAD = "fs.azure.enable.readahead";

hadoop-tools/hadoop-azure/src/main/java/org/apache/hadoop/fs/azurebfs/services/AbfsInputStream.java

@@ -748,7 +748,6 @@ byte[] getBuffer() {
   @VisibleForTesting
   public boolean isReadAheadEnabled() {
     return readAheadEnabled;
-
   }
 
   @VisibleForTesting

hadoop-tools/hadoop-azure/src/main/java/org/apache/hadoop/fs/azurebfs/services/AbfsInputStreamContext.java

@@ -80,7 +80,6 @@ public AbfsInputStreamContext isReadAheadEnabled(
     return this;
   }
 
-
   public AbfsInputStreamContext withReadAheadRange(
           final int readAheadRange) {
     this.readAheadRange = readAheadRange;