The talk discusses the experience of adopting Elixir in the RabbitMQ project, highlighting its benefits such as better extensibility, improved argument validation, and a more sensible standard library compared to Erlang. The transition to Elixir has been well received by the team and quickly adopted by users with little prior experience in Elixir or Erlang. Future plans include expanding the use of Elixir while maintaining some Erlang components, aiming for better integration and fewer redundancies.

1. Adopting Elixir in a 10
Year Old Codebase
Michael Klishin, Pivotal Software Inc.

2. Who am I?

3. Who am I?
• Yada Yada Yada Staff Software Engineer at
Pivotal

4. Who am I?
• Yada Yada Yada Staff Software Engineer at
Pivotal
• RabbitMQ core team member

6. About this talk

7. About this talk
• This is an experience report

8. About this talk
• This is an experience report
• Some arguments may be subjective or team-
specific, YMMV

10. What's the Project?

11. What's the Project?
• RabbitMQ

12. What's the Project?
• RabbitMQ
• Started in 2006, before Elixir (Rebar, Lager,
Cowboy, Ranch, dinosaurs, …) existed

13. What's the Project?
• RabbitMQ
• Started in 2006, before Elixir (Rebar, Lager,
Cowboy, Ranch, dinosaurs, …) existed
• Lots of wheels invented, some are not very round

14. What's the Project?
• RabbitMQ
• Started in 2006, before Elixir (Rebar, Lager,
Cowboy, Ranch, dinosaurs, …) existed
• Lots of wheels invented, some are not very round
• New team with a new perspective on things in
the last ~ 2 years

15. What's the Project?
• 7 engineers + ~ 3 active contributors, all kinds of
backgrounds (Erlang, Java, C#/F#, C, …)

16. What's the Project?
• 7 engineers + ~ 3 active contributors, all kinds of
backgrounds (Erlang, Java, C#/F#, C, …)
• Includes several client libraries we maintain, lots
of plugins

17. What's the Project?
• 7 engineers + ~ 3 active contributors, all kinds of
backgrounds (Erlang, Java, C#/F#, C, …)
• Includes several client libraries we maintain, lots
of plugins
• There are projects at Pivotal that depend on what
we do

19. How do we use Elixir?

20. How do we use Elixir?
• All core CLI tools as of 3.7.0

21. How do we use Elixir?
• All core CLI tools as of 3.7.0
• Experimental plugins

22. How do we use Elixir?
• All core CLI tools as of 3.7.0
• Experimental plugins
• Future tools and plugins

23. How do we use Elixir?
• All core CLI tools as of 3.7.0
• Experimental plugins
• Future tools and plugins
• Recruitment honey pot (discovered accidentally)
😂

25. Why Elixir?

26. Why new CLI tools?
• Homegrown CLI option parser is meh

27. Why new CLI tools?
• Homegrown CLI option parser is meh
• CLI tools are too tied to the server, non-
extensible

28. Why new CLI tools?
• Homegrown CLI option parser is meh
• CLI tools are too tied to the server, non-
extensible
• A project-within-a-project

29. Why Elixir?

30. Why Elixir?
• Elixir's OptionParser seems to be inspired by
Ruby & Python ones

31. Why Elixir?
• Elixir's OptionParser seems to be inspired by
Ruby & Python ones
• Associative data structures in Elixir are a solid
improvement over Erlang's

32. Why Elixir?
• Elixir's OptionParser seems to be inspired by
Ruby & Python ones
• Associative data structures in Elixir are a solid
improvement over Erlang's
• Interoperability with Erlang makes it very easy to
try

33. Why Elixir?
• Elixir's OptionParser seems to be inspired by Ruby
& Python ones
• Associative data structures in Elixir are a solid
improvement over Erlang's
• Interoperability with Erlang makes it very easy to
try
• We had over 50 repos already, one more wouldn't
hurt

34. Why Elixir
• Unicode is not an afterthought

35. Why Elixir
• Unicode is not an afterthought
• More approachable to other teams

36. Why Elixir
• Unicode is not an afterthought
• More approachable to other teams
• A very low risk endeavour for products already
running on BEAM

38. How did it go?

39. How did it go?
• Next feature release will include the new CLI
tools in Elixir

40. How did it go?
• Next feature release will include the new CLI
tools in Elixir
• Close to 70 commands, ~ 750 tests, ~ 8K lines of
code

41. How did it go?
• Next feature release will include the new CLI
tools in Elixir
• Close to 70 commands, ~ 750 tests, ~ 8K lines of
code
• New features: extensibility from plugins, result
set streaming for listing commands, much better
argument validation, …

42. How did it go?
• Next feature release will include the new CLI tools
in Elixir
• Close to 70 commands, ~ 750 tests, ~ 8K lines of
code
• New features: extensibility from plugins, result set
streaming for listing commands, much better
argument validation, …
• Well received by other teams at Pivotal 👍

43. How did it go?

44. How did it go?
• Quickly adopted by folks without prior Elixir and
virtually no Erlang experience 👍

45. How did it go?
• Quickly adopted by folks without prior Elixir and
virtually no Erlang experience 👍
• Very decent standard library 👍

46. How did it go?
• Quickly adopted by folks without prior Elixir and
virtually no Erlang experience 👍
• Very decent standard library 👍
• ExUnit is up there with Spock, RSpec 👍

47. How did it go?
• Quickly adopted by folks without prior Elixir and
virtually no Erlang experience 👍
• Very decent standard library 👍
• ExUnit is up there with Spock, RSpec 👍
• Error messages in Elixir are more sensible 👍

48. How did it go?
• Tooling and dependency management from this
century 👍

49. How did it go?
• Tooling and dependency management from this
century 👍
• Upgrading between Elixir versions was very easy
😍

50. How did it go?
• Tooling and dependency management from this
century 👍
• Upgrading between Elixir versions was very easy
😍
• Some Elixir libraries are better than their Erlang
alternatives 🐼

52. How did it go?

53. How did it go?
• Integration with erlang.mk 😣

54. How did it go?
• Integration with erlang.mk 😣
• Confusing to those spending too much time with
Erlang 😕

55. How did it go?
• Integration with erlang.mk 😣
• Confusing to those spending too much time with
Erlang 😕
• Elixir/Erlang data type mismatches 😣

56. How did it go?
• Integration with erlang.mk 😣
• Confusing to those spending too much time with
Erlang 😕
• Elixir/Erlang data type mismatches 😣
• Some Elixir libraries are a one man show 🤞

57. How did it go?
• Integration with erlang.mk 😣
• Confusing to those spending too much time with
Erlang 😕
• Elixir/Erlang data type mismatches 😣
• Some Elixir libraries are a one man show 🤞
• Elixir skeptics in the community 🤞

59. Cool Elixir features our code
uses

60. Cool Elixir features our code
uses
• Functions

61. Cool Elixir features our code
uses
• Functions
• Modules

62. Cool Elixir features our code
uses
• Functions
• Modules
• Standard library

63. Cool Elixir features our code
uses
• Functions
• Modules
• Standard library
• Streams

64. Cool Elixir features our code
uses
• Functions
• Modules
• Standard library
• Streams
• Macros? Nope.

65. Cool Elixir features our code
uses
• Functions
• Modules
• Standard library
• Streams
• Macros? Nope.
• Agents? Nope.

66. Cool Elixir features our code
uses
• Tasks? No.

67. Cool Elixir features our code
uses
• Tasks? No.
• Sweet frameworks? Nooooooooo.

69. Could we build the same
thing in Erlang?

70. Could we build the same
thing in Erlang?
• Technically, absolutely

71. Could we build the same
thing in Erlang?
• Technically, absolutely
• In terms of perception by potential contributors,
probably not

73. Where do we go from here?

74. Where do we go from here?
• Moar Elixir

75. Where do we go from here?
• Moar Elixir
• Moar Erlang

76. Where do we go from here?
• Moar Elixir
• Moar Erlang
• Fewer unnecessarily reinvented wheels 🙏

78. @michaelklishin

79. Questions?