steveloughran commented on a change in pull request #1898: HADOOP-16852: Report 
read-ahead error back
URL: https://github.com/apache/hadoop/pull/1898#discussion_r405033372
 
 

 ##########
 File path: 
hadoop-tools/hadoop-azure/src/main/java/org/apache/hadoop/fs/azurebfs/services/ReadBufferManager.java
 ##########
 @@ -299,11 +327,32 @@ private void clearFromReadAheadQueue(final 
AbfsInputStream stream, final long re
   }
 
   private int getBlockFromCompletedQueue(final AbfsInputStream stream, final 
long position, final int length,
-                                         final byte[] buffer) {
-    ReadBuffer buf = getFromList(completedReadList, stream, position);
-    if (buf == null || position >= buf.getOffset() + buf.getLength()) {
+                                         final byte[] buffer) throws 
IOException {
+    ReadBuffer buf = getBufferFromCompletedQueue(stream, position);
+
+    if (buf == null) {
       return 0;
     }
+
+    if (buf.getStatus() == ReadBufferStatus.READ_FAILED) {
+      // Eviction of a read buffer is triggered only when a queue request 
comes in
+      // and each eviction attempt tries to find one eligible buffer.
+      // Hence there are chances that an old read-ahead buffer with exception 
is still
+      // available. To prevent new read requests to fail due to such old 
buffers,
+      // return exception only from buffers that failed within last 
THRESHOLD_AGE_MILLISECONDS
+      if ((currentTimeMillis() - (buf.getTimeStamp()) < 
THRESHOLD_AGE_MILLISECONDS)) {
 
 Review comment:
   why 30s? Any way to tune this for test runs?

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