Hi Gabriel, We just talked about this on IRC, so just for other's benefit: With NTP's > -x option we should be able to smear the adjustment (by slowing down the > system clock temporarily) until the leap second is incorporated into the > system time. This avoids non-monotonicity, which is important for systems > that use time to capture causality. It would be great to apply the > adjustment to all nodes of the cassandra cluster at once, so that their > clocks are being slewed in lock-step. >
Unfortunately this was broken in NTP 4.2.6 and only recently discovered: http://bugs.ntp.org/show_bug.cgi?id=2745 (only fixed in current development/pre-releases). Even if we would backport the fixes to our time servers we'd run into problems, since the local time deviation in the "normalisation period" wouldn't be consistent across the nodes of the Cassandra cluster. (chrony fully supports NTP smearing since the 2.0 release (27th April 2015), but that's also not a solution for the upcoming leap second). We'll follow up in a separate mail how to best accomodate the Cassandra cluster. Cheers, Moritz _______________________________________________ Wikitech-l mailing list Wikitech-l@lists.wikimedia.org https://lists.wikimedia.org/mailman/listinfo/wikitech-l
