Re: DBmirror replication - replacement for DBMirror.pl

Just to add - the replacement for DBMirror.pl automatically works out
the schema in use and will replicate using DBmirror from 7.x or from 8.x
(table names all changed!). This is done transparently.

I also wrote a short article at
http://www.whitebeam.org/library/guide/TechNotes/replicate.rhtm

Pete

Peter Wilson wrote:

> Not sure whether this is any use to anyone, or whether this is the
> right list to post to but...
>
> I've just released a C++ implementation of the DBMirror.pl script as
> part of Whitebeam (http://www.whitebeam.org) We had *real*
> performance issues with the Perl implementation replicating large
> fields. It's an almost drop in replacement - except configuration file
> format is difffernt. It's also more fault tolerant than the Perl
> implementation and has some parameters to help distribute the
> replication load over time (if you delete 10,000 rows from a table,
> you don't really want you're main application to grind to a halt as
> replication soak up most of your resource!)
>
> I needed to do this quickly - so it links to the utility classes in
> Whitebeam, things like a string class etc. It wouldn't be too
> difficult to decouple these and if there is any interest I'll do that
> when I get a little spare time. Once it's built though it's entirely
> generic and doesn't use anything else from Whitebeam.
>
> If anyone has contact information for the original DBMirror author
> then I'd like to get in touch.
>
> Would like to get feedback from anyone using DBmirror or thinks this
> would be useful..
>
> Background
> ========
>
> Our Whitebeam application server uses PostgreSQL for back-end data
> storage. We originally used IBM DB2, but ported to Postgres about 3
> years ago, but we never sorted out replication (partly because we were
> using Large Objects). I recently sorted that out and looked around for
> a replication scheme to use - first choice being Slony-I. I couldn't
> get it to work - the configuration scheme just kept claiming half our
> schema tables didn't have primary keys (they did!). Also the
> documentation was virtually non-existent.
>
> Dropping back to DBmirror (which comes with the PostgreSQL
> distribution in the 'contrib' directory) worked fine-ish.
> Unfortunately the replication Perl script was un-usably slow, taking
> minutes to replicate a 100K BYTEA field, which we used to store
> images. The replication Perl script seemed to be rather inefficient,
> using a lot of regular expressions to decode field values etc. Perl
> isn't something I felt too confident in - and I needed a solution
> quickly and hence the C++ implementation
>
> Pete
> --
> Peter Wilson
> YellowHawk : http://www.yellowhawk.co.uk
> Whitebeam : http:/www.whitebeam.org
> -----
>
>
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> TIP 8: explain analyze is your friend
>

--
Peter Wilson
T: 01707 891840
M: 07796 656566
http://www.yellowhawk.co.uk
<http://www.yellowhawk.co.uk>

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