[distcc] Working on several distcc enhancements (take 2)

[Daniel Kegel]

On Sun, 27 Nov 2005, Laurent Calburtin wrote:
> I'm very interested about combining ccache and distcc. I think that  
> would make a huge performance improvement in our situation where many  
> developers are compiling each day roughly the same set of files.
> 
> But installing ccache on each distccd host means as many separate  
> caches.

My plan is to use the hash of the preprocessed source + command line
to decide which server to send the compile job to (in a way that takess
into account server speed properly).  This is very much like
picking the server randomly, but using the hash of the
preprocessed source as the seed.

That way, there's no redundant caching.

That also helps solve the problem of host selectin.

> Ultimately we may want a way for the client to select the "best" host  
> based on different criteria:
> - does it have already the output in cache?
> - does it have a slot available?
> - is it the most powerful?

I considered adding a phase to the protocol to send
just the hash to the server, and only send the real
preprocessed source if the cache didn't hit, but
that optimization can wait for later, I think.
Simply making the server do transparant caching should
be enough of a win for now.

- Dan