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HDFS >> mail # dev >> collision in the naming of '.snapshot' directory between hdfs snapshot and hbase snapshot


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Re: collision in the naming of '.snapshot' directory between hdfs snapshot and hbase snapshot
Please see my last comment on the jira. We can make this work without breaking users who are using HDFS snapshots.

________________________________
 From: Ted Yu <[EMAIL PROTECTED]>
To: [EMAIL PROTECTED]
Cc: [EMAIL PROTECTED]; lars hofhansl <[EMAIL PROTECTED]>
Sent: Tuesday, April 16, 2013 10:00 AM
Subject: Re: collision in the naming of '.snapshot' directory between hdfs snapshot and hbase snapshot
 
Let's get proper release notes for HBASE-8352 .

Either Lars or I can send out notification to user mailing list so that there is enough preparation for this change.

Cheers
On Tue, Apr 16, 2013 at 8:46 AM, Jonathan Hsieh <[EMAIL PROTECTED]> wrote:

I was away from keyboard when I asserted that hdfs snapshot was a hadoop
>2.1 or 3.0 feature.  Apparently it is targeted as a hadoop 2.0.5 feature.
> (I'm a little surprised -- expected this to be a hadoop2 compat breaking
>feature) -- so I agree that this is a bit more urgent.
>
>Anyway, I agree that the fs .snapshot naming convention is long standing
>and should win.
>
>My concern is with breaking compatibility in 0.94 again -- if we don't go
>down the conf variable route,  I consider having docs to properly document
>how to do the upgrade and caveats of doing the upgrade in the docs/release
>notes blocker to hbase 0.94.7.  (specifically mentioning from 0.94.6 to
>0.94.7, and to possibly to 0.95).
>
>Jon.
>
>On Mon, Apr 15, 2013 at 9:00 PM, Ted Yu <[EMAIL PROTECTED]> 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 <[EMAIL PROTECTED]> 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 <[EMAIL PROTECTED]> 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 <[EMAIL PROTECTED]>
>> > 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.