Posted on So 30 Dezember 2007

Avahi/Zeroconf patch for distcc updated

I finally found them time to sit down and update my venerable Avahi/Zeroconf patch for distcc. A patched distcc automatically discovers suitable compiler servers on the local network, without the need to manually configure them. (Announcement).

Here's a quick HOWTO for using a patched distcc like this:

  • Make sure to start distccd (the server) with the new --zeroconf switch, This will make it announce its services on the network.
  • Edit your $HOME/.distcc/hosts and add +zeroconf. This magic string will enable Zeroconf support in the client, i.e. will be expanded to the list of available suitable distcc servers on your LAN.
  • Now set $CC to distcc gcc globally for your login sessions. This will tell all well-behaving build systems to use distcc for compilation (this doesn't work for the kernel, as one notable exception). Even better than setting $CC to distcc gcc is setting it to ccache distcc gcc which will enable ccache in addition to distcc. i.e. stick something like this in your ~/.bash_profile: export CC="ccache distcc gcc"
  • And finally use make -j `distcc -j` instead of plain make to enable parallel building with the right number of concurrent processes. Setting $MAKEFLAGS properly is an alternative option, however is suboptimal if the evalutation is only done once at login time.

If this doesn't work for you than it is a good idea to run distcc --show-hosts to get a list of discovered distcc servers. If this list isn't complete then this is most likely due to mismatching GCC versions or architectures. To check if that's the case use avahi-browse -r _distcc._tcp and compare the values of the cc_machine and cc_version fields. Please note that different Linux distributions use different GCC machine strings. Which is expected since GCC is usually patched quite a bit on the different distributions. This means that a Fedora distcc (the client) will not find a Debian distccd (the server) and vice versa. But again: that's a feature, not a bug.

The new -j and --show-hosts options for distcc are useful for non-zeroconf setups, too.

The patch will automatically discover the number of CPUs on remote machines and make use of that information to better distribute jobs.

In short: Zeroconf support in distcc is totally hot, everyone should have it!

For more information have a look on the announcement of my original patch from 2004 (at that time for the historic HOWL Zeroconf daemon), or read the new announcement linked above.

Distribution packagers! Please merge this new patch into your packages! It would be a pity to withhold Zeroconf support in distcc from your users any longer!

Unfortunately, Fedora doesn't include any distcc packages. Someone should be changing that (who's not me ;-)).

You like this patch? Then give me a kudo on Now that I earned a golden 10 (after kicking Larry Ewing from position 64. Ha, take that Mr. Ewing!), I need to make sure I don't fall into silver oblivion again. ;-)

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