directory-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Howard Chu <...@symas.com>
Subject Re: [Replication] Using time offsets instead of absolute time
Date Tue, 20 Jan 2009 03:05:07 GMT
Alex Karasulu wrote:
> Hi all,
>
> The first thread on replication after Emmanuel's comments started taking
> a turn towards the question of time synchronization across replicating
> servers. Time synchronization is very nice to have and forget about
> while writing the code around replication. And yes we do not have
> control over it since administrators can fudge this up.
>
> Another alternative would be to have all the servers in the cluster
> communicate with one another on occasion to share their current time to
> establish offsets. These offsets (differences in time) between servers
> in replication agreements can be used to correct for any time variance
> we might encounter. Furthermore if the time is adjusted on the hosts,
> the cluster can adjust to time changes.
>
> WDYT?

Doing this accurately requires the same amount of work as NTP, to factor in 
network roundtrip delays etc.

In one of my prior jobs I took this route for a Kerberos client implementation 
on Windows. (Which, if you're curious, is used by Eudora...) Since Kerberos 
would refuse to authenticate a client if its clock was more than 5 minutes 
different from the server, we simply recorded the clock offset of each KDC in 
the client. But - wtf - we had to use SNTP to maintain the offsets anyway...

-- 
   -- Howard Chu
   CTO, Symas Corp.           http://www.symas.com
   Director, Highland Sun     http://highlandsun.com/hyc/
   Chief Architect, OpenLDAP  http://www.openldap.org/project/

Mime
View raw message