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https://issues.apache.org/jira/browse/HADOOP-18184?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17749916#comment-17749916
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ASF GitHub Bot commented on HADOOP-18184:
-----------------------------------------

steveloughran commented on code in PR #5832:
URL: https://github.com/apache/hadoop/pull/5832#discussion_r1280857264


##########
hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/impl/prefetch/CachingBlockManager.java:
##########
@@ -494,19 +546,25 @@ private void addToCacheAndRelease(BufferData data, 
Future<Void> blockFuture,
     prefetchingStatistics.executorAcquired(
         Duration.between(taskQueuedStartTime, Instant.now()));
 
-    if (closed) {
+    if (isClosed()) {
       return;
     }
 
-    if (cachingDisabled.get()) {
+    final int blockNumber = data.getBlockNumber();
+    LOG.debug("Block {}: Preparing to cache block", blockNumber);
+
+    if (isCachingDisabled()) {

Review Comment:
   there's a .get() on the future...which blocks until the data is received. 
the checks on L577 are if caching changed during that time.
   
   added some more comments and reviewed/tuned log messages





> 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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