One question about maxOffset setting

[joezxy]

Hi, in RemoteClockMonitor.MonitorRemoteOffsets() implementation, if node's clock offset goes beyond the maxOffset parameter, this node will Fatalf and suicide.

Parameter maxOffset is set to 250ms by default, any reason for choosing this number?
and as the design goal, Cockroachdb should be geo-distributed, then how to set this number for cross-datacenter deployment if without some infrastructure like Atom/GPS synchronized clock using in Spanner. Does normal NTP work?

Waiting for your clarification..:-)

[tbg]

Hi Joezxy,

the 250ms are a first attempt at hard-coding a number that does well enough
for now. In practice, usually with NTP you should stay well below that -
but there are other events which might push a node over that boundary
(think leap seconds) and even later the offset should be measurable (or
controllable) by linking it up with an API a la TrueTime. I would suggest
that for now you take this part of the code with a grain of salt - it's the
first stab at something that'll see more iterations. I do not expect that
we will ship this out as is when we get to beta, at least not with the bit
of code that could possibly allow for a cluster-wide synchronized suicide.

Best,
Tobias

On Wed, Dec 17, 2014 at 10:19 AM, joezxy [email protected] wrote:

Hi, in RemoteClockMonitor.MonitorRemoteOffsets() implementation, if node's
clock offset goes beyond the maxOffset parameter, this node will Fatalf and
suicide.

Parameter maxOffset is set to 250ms by default, any reason for choosing
this number?
and as the design goal, Cockroachdb should be geo-distributed, then how to
set this number for cross-datacenter deployment if without some
infrastructure like Atom/GPS synchronized clock using in Spanner. Does
normal NTP work?

Waiting for your clarification..:-)

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[tbg]

BTW, for general questions, it's best to just mail directly to [email protected]. I'm closing this here, but feel free to follow-up on the thread.
Cheers,
Tobias

[cockroach-team]

Thanks Tobias