Re: pg_upgrade and rsync

On 01/29/2015 12:26 AM, Josh Berkus wrote:
>> So, for my 2c, I'm on the fence about it.  On the one hand, I agree,
>> it's a bit of a complex process to get right.  On the other hand, it's
>> far better if we put something out there along the lines of "if you
>> really want to, this is how to do it" than having folks try to fumble
>> through to find the correct steps themselves.
> So, here's the correct steps for Bruce, because his current doc does not
> cover all of these.  I really think this should go in as a numbered set
> of steps; the current doc has some steps as steps, and other stuff
> buried in paragraphs.
>
> 1. Install the new version binaries on both servers, alongside the old
> version.
>
> 2. If not done by the package install, initdb the new version's data
> directory.
>
> 3. Check that the replica is not very lagged.  If it is, wait for
> traffic to die down and for it to catch up.
>
> 4. Shut down the master using -m fast or -m smart for a clean shutdown.
>   It is not necessary to shut down the replicas yet.
>
> 5. pg_upgrade the master using the --link option.  Do not start the new
> version yet.
>
> 6. create a data directory for the new version on the replica.  This
> directory should be empty; if it was initdb'd by the installation
> package, then delete its contents.
>
> 7. shut down postgres on the replica.
>
> 8. rsync both the old and new data directories from the master to the
> replica, using the --size-only and -H hard links options.  For example,
> if both 9.3 and 9.4 are in /var/lib/postgresql, do:
>
> rsync -aHv --size-only -e ssh --itemize-changes /var/lib/postgresql/
> replica-host:/var/lib/postgresql/
>
> 9. Create a recovery.conf file in the replica's data directory with the
> appropriate parameters.
>
> 10. Start the master, then the replica
>
>

I find steps 2 and 6 confusing.

cheers

andrew