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mesos-distcc: distcc on Mesos.

Usage:

mesos-distcc [pump] make -jN CC='distcc gcc' CXX='distcc g++'

Alternatively:

./configure CC='distcc gcc' CXX='distcc g++'
mesos-distcc [pump] make -jN

How does this work?

mesos-distcc will introspect the make command to determine the number of distccd workers that need to be run to acheive the desired build parallelism.

Then, the DistCCScheduler is started and connects to a Mesos master specified in your environment or your mesos-distcc.rc file, it will attempt to run distccd servers on Mesos. Once these are running, the make command is run with DISTCC_HOSTS and DISTCC_POTENTIAL_HOSTS set in its environment.

Once compilation is complete, the scheduler tears down the temporary distccd cluster.

Installation

  • Install distcc on your build machine and on all slave machines.
  • Make the Python Mesos eggs available on your build machine and ensure your PYTHONPATH is pointing to them (the easiest way to do this is by running make in the Mesos project). As an example:
PYTHONPATH=/home/bmahler/mesos-0.17.0/build/src/python/dist/mesos-0.17.0-py2.6-linux-x86_64.egg:/home/bmahler/mesos-0.17.0/build/3rdparty/libprocess/3rdparty/protobuf-2.4.1/python/dist/protobuf-2.4.1-py2.6.egg
  • Modify the mesos-distcc.rc file to point to the Mesos master and the location of the distccd binary on your slave machines. Alternatively, these can be set in your environment as MESOS_MASTER and DISTCCD_PATH.
  • Now you can run mesos-distcc:
./configure CC='distcc gcc' CXX='distcc g++'
./mesos-distcc make -j200

FAQ:

Q. mesos-distcc fails with ImportError: No module named mesos.

You'll need to ensure your PYTHONPATH is pointing to the Mesos eggs, for example:

PYTHONPATH=/home/bmahler/mesos-0.17.0/build/src/python/dist/mesos-0.17.0-py2.6-linux-x86_64.egg:/home/bmahler/mesos-0.17.0/build/3rdparty/libprocess/3rdparty/protobuf-2.4.1/python/dist/protobuf-2.4.1-py2.6.egg /home/bmahler/mesos-distcc/mesos-distcc make -j200'

Unfortunately, make install of Mesos does not install these eggs to be detected automatically by Python, see: MESOS-899.

Q. Why can't I run a long-lived distcc cluster?

See the TODOs below. Starting a cluster for each make invocation was a simpler first approach, and more elastic (it avoids keeping distccd daemons running when not in use). A long-lived distcc cluster would either be statically sized, or would need to introspect into the distcc state to determine how to size the cluster.

One downside of the current approach is that there is no sharing of the distccd servers across different builds.

Q. Distcc does not seem to be communicating with the distccd servers.

You will need network access from your client machine to the slave machines (specifically, to the ports being offered as slave resources).

TODOs:

  • Provide a standalone mesos-distcc executable (via PEX?) that does not require the eggs to be available via PYTHONPATH.
  • Do the right thing for large N in make -jN.
  • Allow distcc to be downloaded via a URI rather than requiring installation.
  • Add the ability to run a distcc cluster without invoking make. This would require the ability to query the scheduler for the current set of distccd endpoints.

Benchmark:

I ran a quick performance test to observe the benefits for those without access to server-grade machines. To measure this, I built the Mesos project itself off of sha de4b104c.

This test was done using distcc-3.2rc1.

On a 4 core machine:

$ ../configure
$ time make check -j4 GTEST_FILTER=""
real	13m36.824s
user	43m52.899s
sys		1m46.021s

Using a 4 core machine with mesos-distcc with -j200:

$ ../configure CC=distcc CXX=distcc
$ time mesos-distcc make check -j200 GTEST_FILTER=""
real	7m01.801s
user	244.640s
sys		32.403s

On a 16 core machine:

$ ../configure
$ time make check -j16 GTEST_FILTER=""
real	9m31.985s
user	63m40.918s
sys		4m16.105s

Using mesos-distcc can provide substantial improvements when one does not have access to server-grade machines with a high core count.

The Mesos project is not wide enough to benefit substantially from using distcc. It appears the build is ~30 jobs wide at the widest point. Also, pump mode does not work for Mesos due to:

https://code.google.com/p/distcc/issues/detail?id=40 https://code.google.com/p/distcc/issues/detail?id=16

Projects that are immune to these distcc issues would benefit further when using pump mode. See the distcc documentation for typical project benchmarks.