[ClusterLabs] Possible timing bug in SLES15

[Roger Zhou]

On 10/12/21 3:32 PM, Ulrich Windl wrote:
> Hi!
> 
> I just examined the corosync.service unit in SLES15. It contains:
> # /usr/lib/systemd/system/corosync.service
> [Unit]
> Description=Corosync Cluster Engine
> Documentation=man:corosync man:corosync.conf man:corosync_overview
> ConditionKernelCommandLine=!nocluster
> Requires=network-online.target
> After=network-online.target
> ...
> 
> However the documentation says corosync requires synchronized system clocks.
> With this configuration corosync starts before the clocks are synchronized:

The point looks valid and make sense. Well, sounds like no(or very seldom) 
victim because of it in the real life.

> 
> Oct 05 14:57:47 h16 ntpd[6767]: ntpd 4.2.8p15 at 1.3728-o Tue Jun 15 12:00:00 UTC 2021 (1): Starting
> ...
> Oct 05 14:57:48 h16 systemd[1]: Starting Wait for ntpd to synchronize system clock...
> ...
> Oct 05 14:57:48 h16 corosync[6793]:   [TOTEM ] Initializing transport (UDP/IP Unicast).
> ...
> Oct 05 14:57:48 h16 systemd[1]: Started Corosync Cluster Engine.
> ...
> Oct 05 14:58:10 h16 systemd[1]: Started Wait for ntpd to synchronize system clock.
> Oct 05 14:58:10 h16 systemd[1]: Reached target System Time Synchronized.
> 
> Only pacemaker.service has:
> # /usr/lib/systemd/system/pacemaker.service
> [Unit]
> Description=Pacemaker High Availability Cluster Manager
> Documentation=man:pacemakerd
> Documentation=https://clusterlabs.org/pacemaker/doc/en-US/Pacemaker/2.0/html-single/Pacemaker_Explained/index.html
> 
> # DefaultDependencies takes care of sysinit.target,
> # basic.target, and shutdown.target
> 
> # We need networking to bind to a network address. It is recommended not to
> # use Wants or Requires with network.target, and not to use
> # network-online.target for server daemons.
> After=network.target
> 
> # Time syncs can make the clock jump backward, which messes with logging
> # and failure timestamps, so wait until it's done.
> After=time-sync.target
> ...
> 
> Oct 05 14:58:10 h16 pacemakerd[6974]:  notice: Starting Pacemaker 2.0.4+20200616.2deceaa3a-3.9.1
> But still it does not "Require" time-sync.target...
> 

Actually `After=` is more strict dependency than `Require=`.

> Doesn't corosync need synchronized clocks?

Seems good to have, but low priority.

BR,
Roger



> 
> Regards,
> Ulrich
> 
> 
> 
> _______________________________________________
> Manage your subscription:
> https://lists.clusterlabs.org/mailman/listinfo/users
> 
> ClusterLabs home: https://www.clusterlabs.org/
>