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https://issues.apache.org/jira/browse/HDFS-7990?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14385303#comment-14385303
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Hudson commented on HDFS-7990:
------------------------------

FAILURE: Integrated in Hadoop-Mapreduce-trunk-Java8 #146 (See 
[https://builds.apache.org/job/Hadoop-Mapreduce-trunk-Java8/146/])
HDFS-7990. IBR delete ack should not be delayed. Contributed by Daryn Sharp. 
(kihwal: rev 60882ab26d49f05cbf0686944af6559f86b3417d)
* hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
* 
hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/SimulatedFSDataset.java
* 
hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DNConf.java
* 
hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/TestIncrementalBlockReports.java
* 
hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BPServiceActor.java


> IBR delete ack should not be delayed
> ------------------------------------
>
>                 Key: HDFS-7990
>                 URL: https://issues.apache.org/jira/browse/HDFS-7990
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: namenode
>    Affects Versions: 2.0.0-alpha
>            Reporter: Daryn Sharp
>            Assignee: Daryn Sharp
>             Fix For: 2.8.0
>
>         Attachments: HDFS-7990.patch
>
>
> HDFS-395 added the incremental BR feature.  A concern was avoiding a race 
> condition with ack-ing block invalidates followed by the directory scanner 
> re-adding the block before the async delete service removes the block, 
> possibly resulting in a full BR that includes the previously delete ack-ed 
> block.
> The solution was to batch & delay block deletion acks via a hardcoded 
> interval of 100 * heartbeat interval (default: 5min).  The delay isn't 
> required:
> #  The {{FSDatasetSpi}} tracks blocks pending deletions precisely so the 
> scanner won't re-add the block to the volume map
> # Block receiving, received, and deleted go into the same pending report.  A 
> block received event will trigger an immediate IBR which includes the 
> deletion acks.  Ie. The delay is meaningless for all but a quiescent cluster
> # Failing to promptly report deleted blocks on a quiescent cluster prevents 
> the NN from updating the block maps to remove the locations



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