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?
-- Lars ________________________________ From: Adrien Mogenet <[email protected]> To: user <[email protected]> Sent: Tuesday, December 10, 2013 2:16 PM Subject: Re: Default value for Periodic Flusher Hi guys, 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: > Adrien: > 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 > help. > > Cheers > > > 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 > value? > > > > 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 > on > > 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 > as > > 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 > > > > > > -- Adrien Mogenet http://www.borntosegfault.com
