Christopher Browne cbbrowne at ca.afilias.info
Fri Jan 14 11:50:11 PST 2011
Brad Littlejohn <blittlejohn at posportal.com> writes:
>             After doing a bit of googling on changing the IP address
> of the master and slave database servers being replicated by Slony,
> I’m still a bit confused on how to change the address. To give some
> background, I have 2 servers running PostgreSQL 8.4, and replication
> works fine between the database on each server. These are currently
> connected via crossover cable, just for the initial seed of the
> database (it’s roughly 300GB in size).
>
>  
>
>             The slave database is going to be moved to a DR location,
> and kept up to date real time with Slony; however, the IP address of
> the master and slave servers are going to change. I currently have the
> following set up to set up to do the initial seed:

My first question is why you're using IP addresses, when it's commonly
easier to indirect this via using hostnames.

For instance, if you had, in your DNS configuration, a set of CNAME
values, you could change that, and redirect the traffic without any need
to touch Slony configuration altogether.  Similarly, having A or AAAA
records for your favorite host names would allow using host names rather
than IP addresses.

That being said, it can be meaningful to need to switch configuration
around.

If you change the addresses of servers, you'll need to modify
configuration that Slony uses in three notable places:

 a) Whatever script you use to invoke slon processes need to be changed
    to point to the new addresses.

 b) Any slonik scripts that you use will need to have the "admin
    conninfo" changed to indicate the new addresses.

 c) You will need to run a slonik script (that takes b) into
    consideration!) which runs STORE PATH commands to indicate the new
    addresses.

    That slonik script does not need to take any action other than
    running STORE PATH commands; it should not run:
     - init cluster, because the cluster is already initialized
     - store node, because additional nodes are already present
     - create set, because sets are already initialized

    The shell script you tried to run tried to perform all sorts of
    extra actions in addition to running STORE PATH, and those other
    actions failed.
-- 
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Christopher Browne
"Bother,"  said Pooh,  "Eeyore, ready  two photon  torpedoes  and lock
phasers on the Heffalump, Piglet, meet me in transporter room three"


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