38 lines
1.8 KiB
Markdown
38 lines
1.8 KiB
Markdown
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https://github.com/juxt/aero
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### Explicit and intentional
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Configuration should be explicit, intentful, obvious, but not clever. It
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should be easy to understand what the config is, and where it is
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declared.
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Determining config in stressful situations, for example, while
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diagnosing the cause of a production issue, should not be a
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[wild goose chase](http://en.wiktionary.org/wiki/wild-goose_chase).
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### Avoid duplication ...
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Config files are often duplicated on a per-environment basis, attracting
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all the problems associated with duplication.
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### ... but allow for difference
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When looking at a config file, a reader will usually ask: "Does the value differ from the default, and if so how?". It's clearly better to answer that question in-place.
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### Allow config to be stored in the source code repository ...
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When config is left out of source code control it festers and diverges from the code base. Better to keep a single config file in source code control.
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### ... while hiding passwords
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While it is good to keep config in source code control, it is important to ensure passwords and other sensitive information remain hidden.
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### Config should be data
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While it can be very flexible to have 'clever' configuration 'programs', it can be [unsafe](http://www.learningclojure.com/2013/02/clojures-reader-is-unsafe.html), lead to exploits and compromise security. Configuration is a key input to a program. Always use data for configuration and [avoid turing-complete](http://langsec.org/occupy) languages!
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### Use environment variables sparingly
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We suggest using environment variables judiciously and sparingly, the way Unix intends, and not [go mad](http://12factor.net/config). After all, we want to keep configuration explicit and intentional.
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Also, see these arguments [against](https://gist.github.com/telent/9742059).
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