[distcc] load management

[Daniel Kegel]

Justin Randall wrote:
>>I am planning to start working on adding load management enhancements  ...
> 
>>3) on startup, distcc determines appropriate server to send request to
>>   a) poll all servers in host list - wait until all respond or 0.1
>>seconds, whichever comes first
>>   b) multiply connection count by weight, take minimum result, send
>>request to that server  ...
> 
> The design may be simplified by choosing a coordinator and not changing distcc 
> or distccd. This seems to have been the design philosophy for distcc and 
> ccache -- don't complicate distcc or distccd if some other program can get 
> the job done as well.
> 
> The coordinator can receive pushed load information from clients that 
> front/masquerade distcc, much like ccache and distcc themselves can 
> masquerade cc. When distcc is invoked by the coordinator client, the desired 
> host is specified on the command line as the preferred host, and can fallback 
> to localhost if there are network problems.

Here's a scheme that does what you're suggesting in a slightly different way.

I've been toying with the following idea, which combines load balancing
with fsh-like connection caching.  Let's call it lbfsh.
One scenario would be: running "lbfshd $SHELL" would start
a local server listening on a local-only socket,
put that socket's url in the environment as LBFSH_URL, and run a shell;
when the shell exited, the local server would exit.
The command "lbfsh host cmd ..." would ignore the host argument,
connect to $LBFSH_URL, then execute cmd ... by passing it to the local server rather like fsh
does, except that the local server would pick the remote server to send it to.
To use this with distcc, you'd set DISTCC_RSH to 'lbfsh', and set DISTCC_HOSTS
to anything at all; lbfsh would ignore the host argument.

- Dan