Froze middleware talk

I had given this talk at Deccan Ruby Conf 2017, Pune

Transcript

1. ATUL BHOSALE CODEMANCERS @atul1b
3. Rack middleware
5. 1 5 4 3 2 Web Requests
8. WHY?
9. # Non Thread safe code class Counter def initialize @counter = 0 end def call(_env) counter = @counter sleep 1 counter += 1 @counter = counter [200, { 'Content-Type' => 'text/html' }, ["#{@counter}"]] end end
10. WHAT? • Don’t mutate state • Freeze middleware instances • Use data-structures from concurrent-ruby
12. # Thread safe code class Counter def initialize @atomic = Concurrent::AtomicReference.new(0) end def call(_env) @atomic.update { |v| v + 1 } [200, { 'Content-Type' => 'text/html' }, ["{@atomic}"]] end end
16. use (Class.new do def call(env) @a = 1 if env['PATH_INFO'] == '/a' @app.call(env) end freeze_app end)
17. There is no way to unfreeze a frozen object
18. Thank you