Building an alarm clock
with node.js
or
Hacking vs. Engineering
Felix Geisendörfer 29.09.2011 (v1)
Donnerstag, 29. September 2011

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Welcome to the Siesta
right-after-lunch Session!
Donnerstag, 29. September 2011

Building an alarm clock
with node.js
or
Hacking vs. Engineering
Felix Geisendörfer 29.09.2011 (v1)
Donnerstag, 29. September 2011

@felixge
Twitter / GitHub / IRC
Donnerstag, 29. September 2011

My Problem
• Getting up early in the morning
• That means before 12:00 (noon)
Donnerstag, 29. September 2011

This talk
• How I solved this problem
• Hacking vs. Engineering the solution
Donnerstag, 29. September 2011

Patient History
• 23 years
• Working from home
• Can work any hours
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So why get up early?
• To get more stuff done ...
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Previous attempts
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Behavioral Conditioning
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Flying alarm clock
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Circadian rhythm app (Sleep Cycle)
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Many alarms
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Nothing was working
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Text
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VLC
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pmset
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The Script
https://gist.github.com/1a40a207cf6132f77efa
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sudo ./alarm.js 7 30
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Result
• Reliably waking up at any time
• Get to choose different music every night
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Hacking vs. Engineering
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(Software) Engineering
“Rigorous application of science”
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Hacking
“Playful cleverness”
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Hacking vs. Engineering
this project
Donnerstag, 29. September 2011

Tests?
Engineering: Yes
Hacking: Maybe
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Airtunes?
Engineering:
Implement protocol
Hacking:
Piggyback on iTunes or VLC
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Code
var file = '/my/music/file.mp3';
var vlcPath = '/Applications/VLC.app/Contents/MacOS/VLC';
var vlc = spawn(vlcPath, [
'-R',
'--sout=#transcode {acodec = alac channels = 2, samplerate =
44100}: raop{host=10.0.1.13,volume=255}',
file
]);
vlc.stdout.setEncoding('utf8');
vlc.stderr.setEncoding('utf8');
vlc.stdout.on('data', process.stdout.write);
vlc.stderr.on('data', process.stderr.write);
vlc.on('exit', function(code, signal) {
console.log('vlc exit: %i %s', code, signal);
});
Donnerstag, 29. September 2011

Wakeup from Sleep?
Engineering:
pmset schedule wakeorpoweron <datetime>
Hacking:
pmset schedule wakeorpoweron MTWRFSU
<time>
Donnerstag, 29. September 2011

Code
var powerCmd = sprintf(
'pmset repeat wakeorpoweron MTWRFSU %02d:%02d:00',
powerHour,
powerMinute
);
exec(powerCmd, function(err) {
if (err) throw err;
process.setuid('felix');
});
Donnerstag, 29. September 2011

Turn off speakers?
Engineering:
Install speakers in unreachable place.
Hacking: ?
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Text
Duct Tape
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Duct Tape of Concurrent I/O
Donnerstag, 29. September 2011

Engineering Solution for Concurrency
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Why am I talking about this?
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JS has a very hacker-driven
culture
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Duct tape of the web
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Duct tape of the DOM
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• Hacking is lots of fun, go do it!
• Hacking can be a good solution!
• But be aware that many problems call for
an engineering approach.
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Where we need more
engineering:
• Libraries
• Domain logic
• Performance
Donnerstag, 29. September 2011

TL;DL
• Hack when in doubt
• Engineer when clear
Donnerstag, 29. September 2011

Hacking Engineering
Donnerstag, 29. September 2011

Questions?
@felixge
Donnerstag, 29. September 2011