+1. Well stated Gary. Doing anything else is asking for trouble, and it's preventable.
On 10/26/11 2:39 PM, "Gary Helmling" <[email protected]> wrote: >At the same time, it might be simpler to get your customers/operators >to fix their ntp setups. > >Not having synchronized clocks throughout the cluster will cause >problems in other areas as well. It will make it very difficult to >correlate events in different server logs when troubleshooting >problems (you can't rely on the timestamp as a rough guideline). The >Kerberos infrastructure used by Hadoop and HBase security also >requires synchronized clocks to operate correctly. By default, if the >clock skew between two machines is greater than 5 minutes, it will >reject messages as invalid. So you're likely to experience other >headaches even if you can coax HBase into operating the way you'd >like. > > >On Wed, Oct 26, 2011 at 9:02 AM, Stack <[email protected]> wrote: >> On Tue, Oct 25, 2011 at 7:36 PM, Gaojinchao <[email protected]> >>wrote: >>> So we hope to add a choice about metadata is not time-dependent. Just >>>like use data can use a number as a timestamp . >>> If we can do this, the effect for time will be smaller. We don't use >>>the ntp server, the cluster also can work normal ? >>> Can I open a file? I will try to make a patch and share my mind. >>> >> >> I suppose you could set an attribute on a table that says "use always >> increasing version rather than timestamp". You'd have to then on a >> per region basis keep note of the most recent version and rather than >> use system time, do a +1 per edit coming in. >> >> I think hfile already records the version of the last edit added to >> the file. On open of a region, you'd look at all hfiles and figure >> the highest verison and then set your version machine to start at >> highest-version +1. >> >> It might not be that hard to add. You'd have to check the code but a >> while back we made it so we indirectly got version by going to an >> EnvironmentEdge class. You could add your 'always increasing version' >> as an atomic long or something and then it would be available >> throughout. >> >> St.Ack >>
