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From Ted Yu <yuzhih...@gmail.com>
Subject Re: ICV concurrency problem (?)
Date Sat, 12 Jun 2010 22:00:58 GMT
For #3, take a look at http://en.wikipedia.org/wiki/Network_Time_Protocol

On Sat, Jun 12, 2010 at 2:22 PM, Mark Laffoon <mlaffoon@semanticresearch.com
> wrote:

> I'm not having a lot of success figuring out the pattern. I am most
> definitely not seeing stack traces in any of the logs. I'm not seeing any
> errors in my app logs, although I haven't scoured every log from every
> hadoop/mapreduce/hbase agent in the system (I really need to centralize
> those logs).
>
> However, I have an HBase question that might be related: how are
> timestamps handled/generated?
>
> 1. I have multiple clients (map/reduce task executors) hitting an HBase
> cluster with multiple region servers. Assuming the client code doesn't
> explicitly set the timestamp, which box actually generates the timestamp
> for a put?
>
> 2. If a timestamp for a put (either generated by the client or by whatever
> box) is older than the most recent, and I have maxVersions set to 1, does
> the put get ignored?
>
> 3. If I have an HBase cluster, and the times of the various machines
> aren't in sync, am I just asking for trouble? What do most people do to
> keep their machines in sync?
>
> Thanks,
> Mark
>
> -----Original Message-----
> From: saint.ack@gmail.com [mailto:saint.ack@gmail.com] On Behalf Of Stack
> Sent: Saturday, June 12, 2010 9:59 AM
> To: user@hbase.apache.org
> Subject: Re: ICV concurrency problem (?)
>
> On Fri, Jun 11, 2010 at 4:26 PM, Mark Laffoon
> <mlaffoon@semanticresearch.com> wrote:
> > The other thing I didn't mention: I ran the 80x120000 test a few more
> > times. Sometimes it works, and sometimes it doesn't <sigh>. Could there
> be
> > an issue with data being moved around regions?
> >
>
> So, when it doesn't work, can you figure difference?  Are tasks
> failing?  Are there exceptions in the hbase/tasktracker logs?
>
> St.Ack
>

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