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HBase >> mail # dev >> Pull instant schema updating out?


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Jean-Daniel Cryans 2012-04-02, 23:56
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Stack 2012-04-03, 00:03
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Re: Pull instant schema updating out?
I agree having two implementations seems like a big mess. Any sense
which one is closer to working for the average user (i.e without
provisions like "don't split or crash servers mid-alter")?

On Mon, Apr 2, 2012 at 4:56 PM, Jean-Daniel Cryans <[EMAIL PROTECTED]> wrote:
> Hi nifty devs,
>
> After encountering HBASE-5702, I started playing with instant schema
> updating (HBASE-4213) a bit more and I must say that it's a bit rough
> which makes me wonder... should we pull that code out?
>
> We're in this "interesting" situation in 0.94 where we have two
> different ways to alter tables without disabling them and I don't
> trust either. I'm pretty sure most of the devs don't even know which
> one takes precedence over the other when both are enabled without
> looking at the code. Well, right now hbase.online.schema.update.enable
> needs to be enabled in order to have
> hbase.instant.schema.alter.enabled working. If only the former is
> enabled the master handles the alter, else if both are enabled then
> it's going to be done via ZK although the master still keeps track of
> it.
>
> So the differences between both IIUC:
>
>  - "Online schema update" is a rolling close/open of all the regions
> so that they pick up the new HTD. It's handled by the master and has
> been in since 0.92. I've used it quite a bit when running other tests
> and it's ok as long as regions are not splitting and RS are not
> shutting down. We also enabled it on our clusters here since our
> regions don't tend to move that much.
>
>  - "Instant schema alter" is instant in the sense that all the regions
> are asked to close from the get-go but effectively the region servers
> can only close one region at a time. The state of the alter is kept in
> ZK and the master has a bunch of watches and logs the progress. It's
> new since 0.94 and I'm not sure if anyone is using it. I've tested it
> a bit and at the moment I can say the the MonitedTasks handling needs
> to be redone, it logs way too much information in the log, but the few
> alters I ran worked... It's just a bit hard to know when they're done.
>
> FWIW we could pull either or both out, but instant schema alter hasn't
> been in a released version yet so it's unlikely it'll bother someone
> while the other is already in use (like here).
>
> Opinions?
>
> Thanks,
>
> J-D

--
Todd Lipcon
Software Engineer, Cloudera
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yuzhihong@... 2012-04-03, 00:12
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lars hofhansl 2012-04-03, 01:04
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Stack 2012-04-03, 04:05
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Stack 2012-04-03, 04:38
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Ted Yu 2012-04-03, 04:11
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lars hofhansl 2012-04-03, 06:07
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yuzhihong@... 2012-04-03, 10:20
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Stack 2012-04-03, 14:50
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Andrew Purtell 2012-04-03, 17:19
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lars hofhansl 2012-04-03, 16:14
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Ted Yu 2012-04-03, 16:23
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Stack 2012-04-03, 16:49
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Nicolas Spiegelberg 2012-04-03, 17:34
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Stack 2012-04-04, 16:44
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Ted Yu 2012-04-04, 17:07
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Stack 2012-04-03, 16:35
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Joey Echeverria 2012-04-03, 15:01
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Jean-Daniel Cryans 2012-04-03, 16:43
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Ted Yu 2012-04-03, 01:10
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Andrew Purtell 2012-04-03, 00:45