[Pgcluster-general] FYI: PGCluster-1.9.0rc1 released

[Rick Vernam]

On Tuesday 05 February 2008 07:29:37 pm At.Mitani wrote:
> Hi Rick,
>
> > No Rsync_timeout or Rsync_bwlimit ?
>
> It needs configuration file's change in order to add this parameter.
>
> When the configuration file is changed, I 'd like to do at the same time by
> all versions.
I've written against 1.7-whatever..
If you plan to include in 1.9-whatever, I'll supply a patch against 1.9.0rc1

do you want for 1.5 & 1.3 as well?
>
> By the way,
> When rsync becomes time-out, the recovery function will always fail as you
> know. This is a fatal flaw for the HA system, I think.
Indeed, I agree.  But don't you think that ignoring a failing sub-system is 
even worse?

The problem for me was that rsync would hang indefinitely - I've often waited 
up to 10 or 15 minutes with no activity, even so long as 25 minutes.  
Normally recovery takes less than 5 minutes.
Without using rsync's built-in timeout, when rsync hangs, I have to first kill 
rsync (manually), then kill postmaster (manually).

With my timeout patches applied, rsync would identify that it is hanging, and 
timeout after the specified period of time without activity.
Sure, this causes recovery function to fail - but if rsync is hanging, then to 
fail cleanly, and at the point of failure is much better than to just stop 
and sit there hanging without notification, and requiring an undesirable 
kill.

Furthermore, if I give rsync a low enough bwlimit, rsync does not even hang -  
so clearly bwlimit has it's merits as well.

>
> What do you think about the cause of the rsync failure ?
I believe the cause is high-latency link between nodes, and/or cheap NICs - as 
both are known contributors to rsync issues.
Obviously, one would want to avoid high-latency links and cheap NICs at most 
any cost - but we don't always get what we want...

> Do you have any idea what tool might be an alternative of rsync ?
I've given this plenty of thought, and over a low(er)-latency, and low(er) 
bandwidth link, I think rsync (with all it's options for working through 
harsh environments) is just fine...but clearly, some cases need to use 
additional options of rsync.
>
> Regards,