[Seaside] persistence for lazy people

[Avi Bryant]

On Nov 26, 2005, at 3:10 PM, Ross Boylan wrote:


> Since the image is already an object database, I was thinking of using
> it to serve seaside, with some thread that wakes every 10? minutes and
> does a save.
>
> I'm not, at least at first, going to have a lot of data or users.
>
> Is this a bad idea, or does it qualify as the simplest thing that
> could possible work?
>

It does, absolutely.  It's a great 80% solution when you can get away  
with it.  If you're worried about dropping requests in the couple of  
seconds that the image is saving, see the thread I started on squeak- 
dev a bit ago about forking and snapshotting in the background.  I  
can send you patches for a couple of approaches to this, one which  
still involves a GC and one which lives more dangerously and  
doesn't.  I've been testing both and haven't run into any problems.   
Saving an image then becomes nearly free, and you can probably up the  
frequency to every 2 or 3 minutes instead.

There's still the problem of potentially losing data if the image  
crashes or hangs during those 2 or 3 minutes.  One dead-simple way to  
handle this that seems like it should work in theory, but still  
scares me a bit in practice, is to fully log all of HTTP requests  
that come in.  If you need to, you can then restart the image from  
the last save point and replay those requests.  This could also  
potentially make for a great forensic tool - you could step through  
the requests one by one and hopefully find out *why* the image crashed.

Avi