Should we default it to 0 (off) then? (As Ted pointed out, you can turn this off).
Are you not worried about MTTR when a RegionServer dies with 3GB of logs to replay?
From: Adrien Mogenet <[EMAIL PROTECTED]>
To: user <[EMAIL PROTECTED]>
Sent: Tuesday, December 10, 2013 2:16 PM
Subject: Re: Default value for Periodic Flusher
I've upgraded to 0.94.11. Here is my "worst-case scenario" :
- let say each regionserver has 3 GB memstore
- let say compaction max filesize is ~200 GB, min. 2 files, max 10 files.
- let say memstore is growing "slowly" (1 GB / hour per RS)
Then, automatically flushing every hour will lead into 1 GB storefiles,
being compacted into storefiles of 2 GB, 3 GB, 4.... up to 200 GB.
Sometimes, my write-load becomes very low, and periodic flusher will flush
perhaps 1 MB of data, it will trigger a minor compaction of hundreds
gigabytes + 1 MB; it seems to be lots of IO just to merge 1 MB of data.
Previously (ie. lack of periodic flusher) memstore was creating 3 GB
storefiles, and thus creating (after minor compactions) 3 GB, 6 GB, 9 GB...
up to 200 GB storefiles. And if memstore is growing slowly, it won't
generate small storefiles on HDFS. If think it looks like a more reasonable
IO-load, doesn't it?
I deeply agree with Periodic Flusher relevance, but I don't think it's
suitable for everyone. Do you share my opinion wrt. my workload?
On Sun, Dec 8, 2013 at 10:36 PM, Ted Yu <[EMAIL PROTECTED]> wrote:
> This config was introduced in 0.94.8
> Which release did you upgrade to ?
> As Jean-Marc said, telling us the issue (along with log snippet) would
> On Mon, Dec 9, 2013 at 1:26 AM, Jean-Marc Spaggiari <
> [EMAIL PROTECTED]
> > wrote:
> > Hi Adrien,
> > What was the bad behavior you faced because of that? Maybe it's what need
> > to be fixed more than the periodic flusher? Or put a bigger default
> > JM
> > 2013/12/8 Adrien Mogenet <[EMAIL PROTECTED]>
> > > Hi there,
> > >
> > > I'm wondering if the Periodic Flusher should be disabled by default?
> > >
> > > During a recent upgrade, I've noticed a strange behavior modification
> > my
> > > servers, and it was due to this new feature, supplied with a "1 hour"
> > > default value. I think upgrades should keep default behavior as close
> > in
> > > previous versions. "By chance", logs were mentioning this "Periodic
> > > Flusher" but this could have taken much more time to debug otherwise
> > >
> > > What are you thoughts guys?
> > > (Perhaps should be cc'ed to dev list?)
> > > --
> > > Adrien Mogenet
> > > http://www.borntosegfault.com
> > >