Suppose you're hosting a coding dojo and want to do continuous integration; that is, you want to always show the state of the tests while editing code. Here's a pretty stable solution I came up with after a few tries.

I want to use two projectors: one for showing the test state, the other for showing the code under development. This means using two computers, and that I need to sync between them. If you're using a single machine, then you can still use the same setup, or just leave out the rsync part. A quick summary of what's going in; if you feel like it, this is enough to roll your own:

    inotifywatch / fswatch
             |
             |
        rsync|client
             |                           dev machine
---------+--------------------------------------
             |                            ci machine
        rsync|server
             |
             |
    inotifywatch / fswatch
             |
             |
       compile, test

The things that need to happen in order, when a change is saved on the development machine:

1. inotifywatch / fswatch starts an rsync operation

#!/bin/sh
remote=$1
fswatch . "date +%H:%M:%S && rsync -viru --delete . rsync://$remote/dojo"

This will start fswatch (on OSX; use inotifywatch on Linux), set it to watch pwd, and start an rsync of the directory to the rsync server running on the CI machine. You'll need to pass the host:port of the rsync server to this script. dojo is the name of the rsync module configured on the server (see below).

2. rsync sends changes to the server

An rsync server needs to be running on the CI machine. You can start one simply by doing rsync --daemon --no-detach --config=./rsyncd.conf. The interesting stuff is in ./rsyncd.conf:

pid file = /tmp/dojo-rsyncd.pid
log file = /tmp/dojo-rsyncd.log
address = 0.0.0.0
port = 8873
use chroot = false

[dojo]
path = /tmp/dojo-ci-server
uid = abesto
read only = no

The dojo section is what I hinted at in the previous section. Most of this is pretty self-explanatory. Note that the rsync server logs only to the log file you set here, never to STDOUT. Make sure the directory /tmp/dojo-ci-server is created before you start the server, and that it's writable by the user running the rsync server.

3. The change should trigger build/test on the CI machine

Simply using fswatch:

#!/bin/sh
cd /tmp/dojo-ci-server
fswatch . build-and-test.sh

4. Build, test

This will depend on what technology you're using in the dojo. Using figlet to have a big, nice, ASCII status saying ERROR or FAIL or PASS works very well (the font banner3 is one that's pretty good for this).

Other things I've tried

• sshfs with osxfuse: almost there, but it seems that the mounted file system doesn't support events on OSX, so fswatch doesn't pick up the changes.
• Dropbox: works, but there's a longish delay between the save and the build/test run.

Finally, an example of the whole thing: https://github.com/abesto/bphug-dojo/tree/master/ci