Google Summer of Code
Rails Thread Safety
Joshua Peek

Multi-core Erlang
Motivations
Neverblock
Ruby 1.9
JRuby

Writing thread-safe is hard

Shared Memory

Common Pitfalls

Request Specific Globals
TimeZone.current
I18n.locale

Modifying classes in a thread

Caches!

@@cache
@@file_exist_cache
@@computed_public_paths
@@all_javascript_sources
@@all_stylesheet_sources
@@processed_view_paths
@@file_extension_cache

ActionPack

ActionView rendering logic rewritten

View paths are indexed and all templates are
“compiled” at boot

Dependency Loading

Do nothing

Connection Pool

Previous Implementation
Technically Thread-Safe
ActiveRecord::Base.allow_concurreny = true
One connection per thread
ERROR: Too many connections

Connection Pool
Grows as more connections are needed
Old connections are recycled

Big Thanks to Nick Sieger!

Rails 2.2
Threadsafe! (for the most part)