On Fri, Apr 4, 2008 at 11:09 AM, Craig James <craig_james at emolecules.com> wrote:
>  Yes, I just now got to the bottom of it.  I realized that Slony is not high
> enough quality to use in a production environment, and I'm abandoning it
> until some time in the future when it has matured a bit more.

That should be clarified - Slony is not enough high quality to use in
a production environment _for you_. It works very well for me. It took
a few days of reading docs and testing to get familiar enough with how
Slony works to become comfortable using it in production, and I find
it works great.

In fact, compared to the commercial replication product it replaced,
Slony is the following:

Cheaper (I was paying $25k for a basic replication license per server)
Faster (Replication lag is minimal and so is overhead)
Reliable (Have never had a problem that wasn't caused by me doing
something the docs said not to - and even then I was able to correct
the problem)

>  This is just the last straw.  I really hate to be critical of any
> open-source project, because I genuinely appreciate everyone's hard work.
> But in the end, Slony has proved to be more trouble that it is worth.

It sounds to me that what you really need is a Slony expert - Perhaps
calling up Command Prompt and getting them to help would be a
solution.

>  It's clear to me that Slony's developers are focused on features, and have
> not paid enough attention to the user experience.  It's a classic case where
> the developers, who are experts in their own technology, don't realize just
> how difficult their product is for the mainstream user.

Yes, a spiffy whiz-bang interface to simply things for the mainstream
user would be nice. But that's not going to happen until one of two
things happen:

1. A developer gets an itch and decides to build it.
2. A customer decides to pay a developer to build it.

>  * It is trivially easy to DESTROY an entire database with Slony.  All you
> have to do is a simply typo, reversing node 1 and node 2, and Slony will,
> with no further warning, truncate every table in your master database.

That's really the job of the to be designed whiz-bang interface, not Slony.

>  * Slony's configuration files can contain errors that are only detected
> after many hours, even days, of operation have elapsed. This happened to me
> yesterday: 14 hours after an initial copy-set operation started, it reported
> that one of the slave tables was missing its primary key, something it could
> have reported when the cluster was created.  And often when the error is
> discovered, the only recourse seems to be to uninstall the Slony schema, and
> restart from ground zero.

Checking tables for primary keys before starting copying sounds like a
good idea. Have you filed a bug report?

>  * Slony can encounter errors from which there is no recovery, except to
> blow off the system and start over.  Such as the one I'm facing right now.

I've never seen a problem that absolutely requires one to blow off the
system and start over - but often it is easier to do so rather than
debug the issue.

>  So, best wishes to the Slony team, and keep up the good work.  If my
> comments seem harsh, it's because I care:

Unfortunately, your situation is prevalent with many open source
projects like Slony.

It goes like this:

1. Developers release open source software.
2. Users find open source software rough around the edges or encounters bugs.
3. Users expect instant support to their questions on mailing lists
(hurry, it's production and critical!)
4. Users give up, get mad and leave when the answers do not come while
secretly praying that someone else makes things better while they are
gone.

What can be done?

1. Don't expect fast, free support.
2. If you need fast support from people who know the product inside
and out, pay for it.
3. Paying for support also helps to pay for the development of tools
that can make things easier in the future.

I'm not a Slony developer, just a user, but I do write software for a
living so I know how much time, effort and resources it takes to
create a polished product. So when I do find something that is an
issue I try to make note of it and make it as easy as possible for the
developers to fix it.

-Dave