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From "Jing Zhao (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-9837) BlockManager#countNodes should be able to detect duplicated internal blocks
Date Tue, 23 Feb 2016 19:25:18 GMT

    [ https://issues.apache.org/jira/browse/HDFS-9837?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15159485#comment-15159485

Jing Zhao commented on HDFS-9837:

Thanks for the comments, [~rakeshr]. 

bq. Should be StoredReplicaState.DECOMMISSIONED

Good catch. Will fix it.

bq. I could see BlockInfoStriped#findSlot() is expanding the capacity beyond #getTotalBlockNum.
I think while counting the replicas it is checking only upto totalBlock, so it will miss few
replica checks.

We're using BitSet here thus we're not tracking all the storages (whose total number can exceeds
9) but all the possible internal blocks. Only need to make sure the bitset covers the block
ID range.

bq. use #getStorageInfo(index) instead of storages[index] and storages[i]

I will use {{getStorageInfo(index)}} to replace storages[index] but will keep storages[i]
to keep consistent with indices[i]

> BlockManager#countNodes should be able to detect duplicated internal blocks
> ---------------------------------------------------------------------------
>                 Key: HDFS-9837
>                 URL: https://issues.apache.org/jira/browse/HDFS-9837
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>    Affects Versions: 3.0.0
>            Reporter: Jing Zhao
>            Assignee: Jing Zhao
>         Attachments: HDFS-9837.000.patch, HDFS-9837.001.patch, HDFS-9837.002.patch
> Currently {{BlockManager#countNodes}} only counts the number of replicas/internal blocks
thus it cannot detect the under-replicated scenario where a striped EC block has 9 internal
blocks but contains duplicated data/parity blocks. E.g., b8 is missing while 2 b0 exist:
> b0, b1, b2, b3, b4, b5, b6, b7, b0
> If the NameNode keeps running, NN is able to detect the duplication of b0 and will put
the block into the excess map. {{countNodes}} excludes internal blocks captured in the excess
map thus can return the correct number of live replicas. However, if NN restarts before sending
out the reconstruction command, the missing internal block cannot be detected anymore. The
following steps can reproduce the issue:
> # create an EC file
> # kill DN1 and wait for the reconstruction to happen
> # start DN1 again
> # kill DN2 and restart NN immediately

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