The Thermodynamics of Software Systems – Disclaimers – The Laws

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The Thermodynamics of Software Systems – Disclaimers – The Laws

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SoftwareThermodynamics

Presentation on the similarities between software systems and thermodynamic systems.

On Github davidstanley01 / SoftwareThermodynamics

The Thermodynamics of Software Systems

(yes, really)

David Stanley

  • Sr. Application Developer for MMGY Global
  • @davidstanley01

Disclaimers

  • This analogy assumes a non-trivial softare system.
  • No analogy is perfect. They all break down at some point.
  • This analogy is no different. Some parts are a better fit than others.
  • If it doesn't work, have another drink.

http://www.uni-marburg.de/fb15/ag-germano/research/equations.png

http://s214.photobucket.com/user/anarchy_racing_customz/media/3r6blb_zps48ee9ff7.jpg.html

The Laws

0th Law

If two systems are both in thermal equilibrium with a third then they are in thermal equilibrium with each other.

TRANSLATION: Everyone in the casino must bet.

1st Law

The increase in internal energy of a body is equal to the heat supplied to the body minus work done by the body.

TRANSLATION: In the long run, the house always wins.

2nd Law

Over time, differences in temperature, pressure, and chemical potential decrease in an isolated non-gravitational physical system, leading eventually to a state of thermodynamic equilibrium.

TRANSLATION: In the long run, you can only hope to break even.

3rd Law

The entropy of a perfect crystal at absolute zero is exactly equal to zero.

TRANSLATION: You can't quit.

0th Law - applied

Everything is connected. or Nothing exists in isolation

Everything depends upon something

  • Operating System
  • Database
  • DNS
  • External Services

The circle of life

http://www.fanpop.com/clubs/the-lion-king/images/15385011/title/lion-king-part-1-circle-life-screencap

Self-reliance, sort of

Code defensively Fail gracefuly

Defensive coding

Default clauses on switch statements

Validate inputs and encode outputs

Log errors and LOOK AT THE LOG

Write tests that cover edge cases, too

Fail gracefully

Whoops

https://github.com/filp/whoops

1st Law - applied

Value = Utility Generated - Maintenance Effort

Mass can neither be created nor destroyed. It can only change forms.

http://wrightimc.com/wp-content/uploads/2012/08/OneDoesNot.jpg

Build for maintenance and change Set the next developer up for success

Yes, it takes time

http://devopsreactions.tumblr.com/post/40246654962/refactoring-the-code

Build for Maintenance and Change

Archetectural decisions Modularity and Dependency Management 20 lines per method / 200 lines per class Return something, anything

Set the next developer up for success

Doc Blocks Type-hint wherever possible No hidden side-effects COMMENT CODE

From wp-admin/upload.php

From wp-admin/upload.php

http://devopsreactions.tumblr.com/post/47445617308/when-french-homeland-intelligence-forced-wikipedia-fr

2nd Law - applied

Entropy

http://devopsreactions.tumblr.com/post/54501133692/codebase-over-time

Fighting Code Entropy

Have a coding standard and use it. Code Review Write tests! Use automated tools to enforce standards

Coding Standards

PSR 1 or 2 Zend Wordpress Drupal PEAR

Code Review

Have someone review your work and ask you critical questions.

No time for ego...

http://commadot.com/wtf-per-minute/

Write Tests

The unknown bugs Build with testability in mind Code review on tests, too

Not like this

http://devopsreactions.tumblr.com/post/52368854242/writing-unit-tests

Use the tools we have available

PHPDocumentor PHP Mess Detector PHP Copy/Paste Detector Use your CI tool to automatically run these tests

3rd Law - applied

Every non-trivial system in the wild that provides value requires some measure of maintenance and feeding.

Manage the exceptions

Logging Interface Notify on threshold Back that mo-fo up

Questions?