Dane Miller <dane at greatschools.net> wrote:
>
> Bill Moran wrote:
> > I've been putting this together over the last couple weeks for
> > the reasons listed on the HTML page:
> > http://people.collaborativefusion.com/~wmoran/PostgreSQL/slony_switchover.html
> > 
> > I'm interested to hear how useful this is to others, and of course
> > suggestions for improvement are welcome.

[snip]

> You put a 'wait for event' command after 'lock set' *and* 'move set'.
> slonik_move_set only waits after 'lock set'.  Is this extra wait
> necessary?  If so, should it be fixed in slonik_move_set?  I'm using
> this version:
>    slonik_move_set.pl,v 1.1.4.1 2006-10-27 17:54:21

The rationale behind that is that the shell script doesn't exit until
the move set() is complete.  I _believe_ the slonik move set() command
can return once the event is submitted, even though the operation is
not complete.  I don't want this -- I want the operation to feel confident
that the operation is complete when the command returns.

If I'm wrong about move set()'s behaviour, then this last wait is unneeded.
I'll try to make time to test this next week.

> you state here
> http://people.collaborativefusion.com/~wmoran/PostgreSQL/slony_switchover.html that...
> > Our network topology causes connection paths to vary depending on
> > where you're running the slonik script from, thus each node would need
> > its own slonik script that was different than other nodes
> 
> So there's more than one way to connect to a given node?  Can you
> explain this further?  What kind of network topology do you have that
> necessitates having connection paths that vary?  (I obviously need to
> read more slony documentation)

Each of our DB servers has multiple IP addresses and firewall policies
dictate who can talk to who.  For example, two DB servers in the same
data center will talk directly to each other on their DB IPs, whereas
a DB server in another facility will have to go through two firewalls
and connect to another DB's management IP.  In somewhat less abstract
terms, if I have 3 servers:
db0 - datacenter 1
db1 - datacenter 1
db2 - datacenter 2

If I execute slonik commands from db1, it will use the hostname
db0-db to connect to db0, but db2 will use the hostname db0-mgmnt.

Are you running Linux by any chance?  This script was developed and
is deployed for us on FreeBSD, and I've verified that it works as
advertised on that platform.  I've _attempted_ to make sure that it
will work on Linux as well, but I've not had the opportunity to test
it.  Testing and feedback is encouraged.

-- 
Bill Moran
Collaborative Fusion Inc.

wmoran at collaborativefusion.com
Phone: 412-422-3463x4023

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