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From Ted Yu <yuzhih...@gmail.com>
Subject Re: collision in the naming of '.snapshot' directory between hdfs snapshot and hbase snapshot
Date Tue, 16 Apr 2013 04:17:43 GMT
I have a patch which touched these tests:

http://pastebin.com/P4p8LEAZ

I am running 0.94 test suite now - will publish patch and test result in
the morning.

Cheers

On Mon, Apr 15, 2013 at 9:00 PM, Ted Yu <yuzhihong@gmail.com> wrote:

> bq. Alternatively, we can detect the underlying Hadoop version, and use
> either .snapshot or .hbase_snapshot in 0.94 depending on h1 & h2.
>
> I think this would introduce more confusion, especially for operations.
>
> Cheers
>
> On Mon, Apr 15, 2013 at 8:52 PM, Enis Söztutar <enis.soz@gmail.com> wrote:
>
>> Because HDFS exposes the snapshots so that the normal file system
>> operations are mapped inside snapshot dirs, I think HDFS reserving the
>> .snapshot name makes sense. OTOH, nothing is specific about the dir name
>> that is chosen by HBase.
>>
>> I would prefer to change the dir name in 0.94 as well, since 0.94 is also
>> being run on top of hadoop 2. Alternatively, we can detect the underlying
>> Hadoop version, and use either .snapshot or .hbase_snapshot in 0.94
>> depending on h1 & h2.
>>
>> Enis
>>
>>
>> On Mon, Apr 15, 2013 at 8:31 PM, Ted Yu <yuzhihong@gmail.com> wrote:
>>
>> > bq. let's make the hbase snapshot for a conf variable.
>> >
>> > Once we decide on the new name of snapshot directory, we should still
>> use
>> > hardcoded value. This aligns with current code base:
>> > See this snippet from HConstants:
>> >
>> >   public static final List<String> HBASE_NON_TABLE_DIRS =
>> >
>> >     Collections.unmodifiableList(Arrays.asList(new String[] {
>> > HREGION_LOGDIR_NAME,
>> >
>> >       HREGION_OLDLOGDIR_NAME, CORRUPT_DIR_NAME, SPLIT_LOGDIR_NAME,
>> >
>> >       HBCK_SIDELINEDIR_NAME, HFILE_ARCHIVE_DIRECTORY, SNAPSHOT_DIR_NAME,
>> > HBASE_TEMP_DIRECTORY }));
>> > Cheers
>> >
>> > On Mon, Apr 15, 2013 at 8:24 PM, Jonathan Hsieh <jon@cloudera.com>
>> wrote:
>> >
>> > > constraints:
>> > >
>> > > 1) hbase 0.94.6 is released and .snapshot is hardcoded in there.
>> > > 2) hdfs snapshots is a Hadoop 2.1 or 3.0 feature. I doubt that it will
>> > ever
>> > > make it to 1.x.  This hdfs feature ideally this shouldn't affect
>> current
>> > A
>> > > pache Hbase 0.94.x's.
>> > > 3) hbase 95/96 may default to Hadoop1 or Hadoop 2. these versions
>> should
>> > > pick a different table snapshot name to respect fs conventions.
>> > >
>> > > proposed actions:
>> > >
>> > > 1) let's make the hbase snapshot for a conf variable. (hbase.
>> > > snapshots.dir)  let's change the default for hbase 95+. (maybe
>> > > .hbase-snapshots). we'll also port this patch to 0.94.x
>> > > 2) let's publish instructions on how to update the hbase snapshot dir:
>> > > shutdown hbase, config update, rename dir, restart hbase.
>> > > 3) I lean towards leaving the current default hbase snapshot dir in 94
>> > > since it shouldn't be affected.  upgrading hbase to 95/96 will require
>> > > shutdown and update scripts so it seems like the ideal time to
>> autoforce
>> > > this default change.
>> > >
>> > > Thoughts?
>> > >
>> > >
>> > > On Monday, April 15, 2013, lars hofhansl wrote:
>> > >
>> > > > OK. Let's try to fix that quickly, so that I can release HBase
>> 0.94.7.
>> > > >
>> > > > -- Lars
>> > > >
>> > > >
>> > > >
>> > > > ________________________________
>> > > >  From: Ted Yu <yuzhihong@gmail.com>
>> > > > To: dev@hbase.apache.org; hdfs-dev@hadoop.apache.org
>> > > > Sent: Monday, April 15, 2013 7:13 PM
>> > > > Subject: collision in the naming of '.snapshot' directory between
>> hdfs
>> > > > snapshot and hbase snapshot
>> > > >
>> > > >
>> > > > Hi,
>> > > > This afternoon Huned ad I discovered an issue while playing with
>> HBase
>> > > > Snapshots on top of Hadoop's Snapshot branch (
>> > > > http://svn.apache.org/viewvc/hadoop/common/branches/HDFS-2802/).
>> > > >
>> > > > HDFS (built from HDFS-2802 branch) doesn't allow paths with
>> .snapshot
>> > as
>> > > a
>> > > > component while HBase tries to create paths with .snapshot as a
>> > > component.
>> > > > This leads to issues in HBase, and one of HDFS or HBase needs to
>> give
>> > up
>> > > > the .snapshot reserved keyword. HBase released Snapshots feature in
>> > > 0.94.6
>> > > > (quite recently) and it may not be too late to change HBase to use
a
>> > > > different path component in an upcoming new release.
>> > > >
>> > > > In HBase these path names are not user visible. If there is a
>> > deployment
>> > > of
>> > > > 0.94.6, one could provide a migration tool that renames .snapshot
to
>> > > > .hbase-snapshot or something to be able to move to the Snapshot
>> release
>> > > of
>> > > > Hadoop. On the other hand, .snapshot in HDFS is a user visible name
>> and
>> > > is
>> > > > a convention that is used by many file systems. It's a matter of
>> > > > familiarity with such path names that would help users in using HDFS
>> > > > snapshots.
>> > > >
>> > > > I am including the hdfs-dev in this email. Would appreciate if we
>> could
>> > > > work together and come up with a solution.
>> > > >
>> > > > You can find sample output from hdfs command here:
>> > > > http://pastebin.com/bBqR4Fvr
>> > > >
>> > > > Cheers
>> > >
>> > >
>> > >
>> > > --
>> > > // Jonathan Hsieh (shay)
>> > > // Software Engineer, Cloudera
>> > > // jon@cloudera.com
>> > >
>> >
>>
>
>

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