Tracing on the shoulders of giants

Jacek Królikowski

@nietaki

Story time!

"The eager rate-limter"

"Standard approach"

    

    def suspicious_function(arg1, arg2, opts \\ []) do
      IO.inspect {arg1, arg2, opts}  # Logging the arguments
    
      # do some work here
      # ret = do_some_more_work()  
    
      IO.inspect ret
    end

Debugging, the Erlang way

  • "trace bifs" (erlang:trace_pattern/3)
    • very powerful
    • very not user friendly
  • OTP dbg
    • still not very user friendly
    • it's easy to overload the node
  • redbug (!)
    • easy to use
    • production-friendly
    • still very powerful

:redbug example in Erlang

https://massemanet.github.io/eper/redbug

(Audience participation)

  • :ets.lookup
  • Acme.Palindrome.is_palindrome?("don't nod")

https://github.com/nietaki/tracing-on-the-shoulders-interactive/

Rate-limiting story conclusion

redbug is great anyways!

Birth of

  • Elixir syntax
  • the same redbug power*
    • argument matching
    • remote nodes
    • targetting individual processes
  • analogous API, you can use them interchangeably
  • now available on hex.pm!

Takeaways

Links