[gtld-tech] "last update of RDAP database"

Brian Mountford mountford at google.com
Thu Aug 11 18:25:40 UTC 2016

ICANN RDAP tech folks,

I wanted to comment on an aspect of the ICANN operational profile. 1.4.12,
1.4.13 and 1.5.14 indicate that domains, nameservers and entities should
include an event with type "last update of RDAP database". It sounds like
you are assuming that the database will have a timestamp as of which all
data are consistent, like a snapshot. Modern distributed databases don't
necessarily have such a timestamp. If the database is "eventually
consistent" (see https://en.wikipedia.org/wiki/Eventual_consistency),
updates to a particular object may not show up in database reads until some
time later. Technically, the only guarantee is that the new, updated value
will show up eventually.

So when we return a "last update time", that doesn't mean that the data
being returned in the RDAP response is as fresh as what was written on or
before the last update time. The read may lag behind the update. I am going
to go ahead and set the last update time to the current time, because
that's when the most recent update could have occurred. But that will not
mean that the returned data is current as of that time, because such a
guarantee is impossible in an eventually consistent database.


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