Tips from @rasmus about atomic deployments...

notes.md

The only way to have atomic (code) deploys:

• Don't copy files into current document root
• Let existing requests finish on old code
• New requests start on new code
• Avoid clearing your opcode cache
• Minimal impact on production traffic

Breakdown:

• two DOCUMENT_ROOT directories: A & B
• symlink DOCUMENT_ROOT toggles between them
• use realpath() symlink at the web server level
• set DOCUMENT_ROOT to symlinked realpath
• never hardcode DOCUMENT_ROOT in code

How do you do that?

• Apache: http://github.com/etsy/mod_realdoc
• nginx: fastcgi_param DOCUMENT_ROOT $realpath_root
• Hacky PHP: https://github.com/etsy/incpath