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https://issues.apache.org/jira/browse/HADOOP-18184?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17746944#comment-17746944
 ] 

ASF GitHub Bot commented on HADOOP-18184:
-----------------------------------------

steveloughran commented on code in PR #5832:
URL: https://github.com/apache/hadoop/pull/5832#discussion_r1273422607


##########
hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/impl/prefetch/CachingBlockManager.java:
##########
@@ -392,16 +413,41 @@ private void readBlock(BufferData data, boolean 
isPrefetch, BufferData.State...
           ops.end(op);
         }
 
-        if (isPrefetch) {
-          prefetchingStatistics.prefetchOperationCompleted();
-          if (tracker != null) {
-            tracker.close();
-          }
+        // update the statistics
+        prefetchingStatistics.fetchOperationCompleted(isPrefetch, 
bytesFetched);
+        if (tracker != null) {
+          tracker.close();
+          LOG.debug("fetch completed: {}", tracker);
         }
       }
     }
   }
 
+  /**
+   * True if the manager has been closed.
+   */
+  private boolean isClosed() {
+    return closed.get();
+  }
+
+  /**
+   * Disable caching; updates stream statistics and logs exactly once
+   * at info
+   * @param endOp operation which measured the duration of the write.
+   */
+  private void disableCaching(final BlockOperations.End endOp) {
+    if (!cachingDisabled.getAndSet(true)) {
+      String message = String.format(
+          "Caching disabled because of slow operation (%.1f sec)", 
endOp.duration());
+      LOG_CACHING_DISABLED.info(message);
+      prefetchingStatistics.setPrefetchCachingState(false);

Review Comment:
   done in method, but not in gauge name. What if we ever allow a cache to 
memory option here?





> s3a prefetching stream to support unbuffer()
> --------------------------------------------
>
>                 Key: HADOOP-18184
>                 URL: https://issues.apache.org/jira/browse/HADOOP-18184
>             Project: Hadoop Common
>          Issue Type: Sub-task
>          Components: fs/s3
>    Affects Versions: 3.4.0
>            Reporter: Steve Loughran
>            Assignee: Steve Loughran
>            Priority: Minor
>              Labels: pull-request-available
>
> Apache Impala uses unbuffer() to free up all client side resources held by a 
> stream, so allowing it to have a map of available (path -> stream) objects, 
> retained across queries.
> This saves on having to reopen the files, with the cost of HEAD checks etc. 
> S3AInputStream just closes its http connection. here there is a lot more 
> state to discard, but all memory and file storage must be freed.
> until this done, ITestS3AContractUnbuffer must skip when the prefetch stream 
> is used.
> its notable that the other tests don't fail, even though the stream doesn't 
> implement the interface; the graceful degradation handles that. it should 
> fail if the test xml resource says the stream does it, but that the stream 
> capabilities say it doesn't.



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