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https://issues.apache.org/jira/browse/HDFS-13165?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16394840#comment-16394840
 ] 

Rakesh R commented on HDFS-13165:
---------------------------------

Thanks [~umamaheswararao] for the comments.
{quote}Why not adding to exclude nodes?
{quote}
I'm adding all the source nodes to the exclude nodes list so that these nodes 
won't be chosen as remote node later. Does this make sense to you?
{code:java}
StoragepolicySatisfier.java class

      // Add existing storages into exclude nodes to avoid choosing this as
      // remote target later.
      List<DatanodeInfo> excludeNodes = new ArrayList<>(existingBlockStorages);
{code}
{quote}If no, need to check spa manager null checks.
{quote}
Yes, I thought of avoiding null checks. But I understand your point of zero 
cost if the feature is disabled. I've done the changes and added null checks in 
the latest patch.

Attached another patch addressing comments. Please review it again.

> [SPS]: Collects successfully moved block details via IBR
> --------------------------------------------------------
>
>                 Key: HDFS-13165
>                 URL: https://issues.apache.org/jira/browse/HDFS-13165
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>            Reporter: Rakesh R
>            Assignee: Rakesh R
>            Priority: Major
>         Attachments: HDFS-13165-HDFS-10285-00.patch, 
> HDFS-13165-HDFS-10285-01.patch, HDFS-13165-HDFS-10285-02.patch, 
> HDFS-13165-HDFS-10285-03.patch, HDFS-13165-HDFS-10285-04.patch
>
>
> This task to make use of the existing IBR to get moved block details and 
> remove unwanted future tracking logic exists in BlockStorageMovementTracker 
> code, this is no more needed as the file level tracking maintained at NN 
> itself.
> Following comments taken from HDFS-10285, 
> [here|https://issues.apache.org/jira/browse/HDFS-10285?focusedCommentId=16347472&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-16347472]
> Comment-3)
> {quote}BPServiceActor
> Is it actually sending back the moved blocks? Aren’t IBRs sufficient?{quote}
> Comment-21)
> {quote}
> BlockStorageMovementTracker
> Many data structures are riddled with non-threadsafe race conditions and risk 
> of CMEs.
> Ex. The moverTaskFutures map. Adding new blocks and/or adding to a block's 
> list of futures is synchronized. However the run loop does an unsynchronized 
> block get, unsynchronized future remove, unsynchronized isEmpty, possibly 
> another unsynchronized get, only then does it do a synchronized remove of the 
> block. The whole chunk of code should be synchronized.
> Is the problematic moverTaskFutures even needed? It's aggregating futures 
> per-block for seemingly no reason. Why track all the futures at all instead 
> of just relying on the completion service? As best I can tell:
> It's only used to determine if a future from the completion service should be 
> ignored during shutdown. Shutdown sets the running boolean to false and 
> clears the entire datastructure so why not use the running boolean like a 
> check just a little further down?
> As synchronization to sleep up to 2 seconds before performing a blocking 
> moverCompletionService.take, but only when it thinks there are no active 
> futures. I'll ignore the missed notify race that the bounded wait masks, but 
> the real question is why not just do the blocking take?
> Why all the complexity? Am I missing something?
> BlocksMovementsStatusHandler
> Suffers same type of thread safety issues as StoragePolicySatisfyWorker. Ex. 
> blockIdVsMovementStatus is inconsistent synchronized. Does synchronize to 
> return an unmodifiable list which sadly does nothing to protect the caller 
> from CME.
> handle is iterating over a non-thread safe list.
> {quote}



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