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https://issues.apache.org/jira/browse/HDFS-14514?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16851419#comment-16851419
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Daniel Templeton commented on HDFS-14514:
-----------------------------------------
LGTM. I'd like to see the last two {{if}}s in {{DFSInputStream}} be an
{{if/else-if}}, but I can fix that on commit. If there are no complaints, I'll
commit this later this evening.
> 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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