spark git commit: [SPARK-4714] BlockManager.dropFromMemory() should check whether block has been removed after synchronizing on BlockInfo instance.

[joshrosen]

Repository: spark
Updated Branches:
  refs/heads/branch-1.1 fe7d7a983 -> 9b9923744


[SPARK-4714] BlockManager.dropFromMemory() should check whether block has been 
removed after synchronizing on BlockInfo instance.

After synchronizing on the `info` lock in the 
`removeBlock`/`dropOldBlocks`/`dropFromMemory` methods in BlockManager, the 
block that `info` represented may have already removed.

The three methods have the same logic to get the `info` lock:
```
   info = blockInfo.get(id)
   if (info != null) {
     info.synchronized {
       // do something
     }
   }
```

So, there is chance that when a thread enters the `info.synchronized` block, 
`info` has already been removed from the `blockInfo` map by some other thread 
who entered `info.synchronized` first.

The `removeBlock` and `dropOldBlocks` methods are idempotent, so it's safe for 
them to run on blocks that have already been removed.
But in `dropFromMemory` it may be problematic since it may drop block data 
which already removed into the diskstore, and this calls data store operations 
that are not designed to handle missing blocks.

This patch fixes this issue by adding a check to `dropFromMemory` to test 
whether blocks have been removed by a racing thread.

Author: hushan[胡珊] <hus...@xiaomi.com>

Closes #3574 from suyanNone/refine-block-concurrency and squashes the following 
commits:

edb989d [hushan[胡珊]] Refine code style and comments position
55fa4ba [hushan[胡珊]] refine code
e57e270 [hushan[胡珊]] add check info is already remove or not while having 
gotten info.syn

(cherry picked from commit 30dca924df0efbdc1b638fa7c705fe8743570783)
Signed-off-by: Josh Rosen <joshro...@databricks.com>


Project: http://git-wip-us.apache.org/repos/asf/spark/repo
Commit: http://git-wip-us.apache.org/repos/asf/spark/commit/9b992374
Tree: http://git-wip-us.apache.org/repos/asf/spark/tree/9b992374
Diff: http://git-wip-us.apache.org/repos/asf/spark/diff/9b992374

Branch: refs/heads/branch-1.1
Commit: 9b99237441c355179dbea2662c5baef0cef82e5d
Parents: fe7d7a9
Author: hushan[胡珊] <hus...@xiaomi.com>
Authored: Tue Dec 9 15:11:20 2014 -0800
Committer: Josh Rosen <joshro...@databricks.com>
Committed: Tue Dec 9 15:55:10 2014 -0800

----------------------------------------------------------------------
 core/src/main/scala/org/apache/spark/storage/BlockManager.scala | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)
----------------------------------------------------------------------


http://git-wip-us.apache.org/repos/asf/spark/blob/9b992374/core/src/main/scala/org/apache/spark/storage/BlockManager.scala
----------------------------------------------------------------------
diff --git a/core/src/main/scala/org/apache/spark/storage/BlockManager.scala 
b/core/src/main/scala/org/apache/spark/storage/BlockManager.scala
index 3113d4a..881b956 100644
--- a/core/src/main/scala/org/apache/spark/storage/BlockManager.scala
+++ b/core/src/main/scala/org/apache/spark/storage/BlockManager.scala
@@ -975,8 +975,10 @@ private[spark] class BlockManager(
           // If we get here, the block write failed.
           logWarning(s"Block $blockId was marked as failure. Nothing to drop")
           return None
+        } else if (blockInfo.get(blockId).isEmpty) {
+          logWarning(s"Block $blockId was already dropped.")
+          return None
         }
-
         var blockIsUpdated = false
         val level = info.level
 


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