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From "Stephen O'Donnell (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HDFS-14514) Actual read size of open file in encryption zone still larger than listing size even after enabling HDFS-11402 in Hadoop 2
Date Wed, 29 May 2019 17:15:00 GMT

     [ https://issues.apache.org/jira/browse/HDFS-14514?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel

Stephen O'Donnell updated HDFS-14514:
    Attachment: HDFS-14514.branch-2.003.patch

> Actual read size of open file in encryption zone still larger than listing size even
after enabling HDFS-11402 in Hadoop 2
> --------------------------------------------------------------------------------------------------------------------------
>                 Key: HDFS-14514
>                 URL: https://issues.apache.org/jira/browse/HDFS-14514
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: encryption, hdfs, snapshots
>    Affects Versions: 2.6.5, 2.9.2, 2.8.5, 2.7.7
>            Reporter: Siyao Meng
>            Assignee: Siyao Meng
>            Priority: Major
>         Attachments: HDFS-14514.branch-2.001.patch, HDFS-14514.branch-2.002.patch, HDFS-14514.branch-2.003.patch
> In Hadoop 2, when a file is opened for write in *encryption zone*, taken a snapshot and
appended, the read out file size in the snapshot is larger than the listing size. This happens
even when immutable snapshot HDFS-11402 is enabled.
> Note: The refactor HDFS-8905 happened in Hadoop 3.0 and later fixed the bug silently
(probably incidentally). Hadoop 2.x are still suffering from this issue.
> Thanks [~sodonnell] for locating the root cause in the codebase.
> Repro:
> 1. Set dfs.namenode.snapshot.capture.openfiles to true in hdfs-site.xml, start HDFS cluster
> 2. Create an empty directory /dataenc, create encryption zone and allow snapshot on it
> {code:bash}
> hadoop key create reprokey
> sudo -u hdfs hdfs dfs -mkdir /dataenc
> sudo -u hdfs hdfs crypto -createZone -keyName reprokey -path /dataenc
> sudo -u hdfs hdfs dfsadmin -allowSnapshot /dataenc
> {code}
> 3. Use a client that keeps a file open for write under /dataenc. For example, I'm using
Flume HDFS sink to tail a local file.
> 4. Append the file several times using the client, keep the file open.
> 5. Create a snapshot
> {code:bash}
> sudo -u hdfs hdfs dfs -createSnapshot /dataenc snap1
> {code}
> 6. Append the file one or more times, but don't let the file size exceed the block size
limit. Wait for several seconds for the append to be flushed to DN.
> 7. Do a -ls on the file inside the snapshot, then try to read the file using -get, you
should see the actual file size read is larger than the listing size from -ls.
> The patch and an updated unit test will be uploaded later.

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