El documento presenta Flow-Based Programming (FBP) utilizando la biblioteca Flowex en Elixir, que permite modelar aplicaciones como un grafo de procesos independientes. Explora los conceptos básicos de FBP, sus ventajas, y cómo Flowex facilita la programación paralela y la reutilización de componentes. Además, se discuten herramientas para ejecutar programas externos y se presenta un ejemplo de componentes multilenguaje que combinan Ruby, Python y Shell.

1. Multi-language
FBP with Flowex
#pivorak 21, Elixir edition, March 24, 2017

2. Hello!
I am Anton Mishchuk
▷ Ruby developer at Matic Insurance Services
(we are hiring!)
▷ A big fan of Elixir programming language
▷ Author and maintainer of:
ESpec and Flowex libraries
github: antonmi
2

3. Preface
Flow-based programming with Elixir
3

4. Preface
Flowex - FBP with Elixir GenStage
4

5. What’s next?
▷ Let Elixir do what it does best
▷ The rest can be implemented in
any other programming language
5

6. Agenda
▷ Quick intro to FBP
▷ Flowex library overview
▷ Tools for running external programs
▷ Multi-language components example:
Ruby, Python, shell
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7. 1.
Flow-Based Programming
Basic concepts
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8. Flow-Based Programming is
a programming paradigm which
models application as a graph of
independent processes exchanging
data across predefined connections
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9. FBP diagram
A
B
D
C
IN 1
IN 1
IN 1
IN 2
IN 1
IN 2
OUT 1
OUT 2
OUT 1
OUT 1
OUT 1
9

10. FBP advantages
▷ Parallelism are natural
▷ No problems associated with shared
memory and locks
▷ Visualisation of data flow networks is simple
▷ Components are independent and reusable
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11. Two layers in FBP application
▷ “Bottom layer” - set of components
implementing parts of business
logic
▷ “Top layer” - “communication logic”
- an organization of data flows
from one component to another
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12. “Bottom layer” - components
▷ Component is independent unit
with input and output
▷ The only thing it does - transform
input IP to output IP
▷ In general, can be implemented
using any programming language
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13. “Top layer” - communication
▷ Need “coordination language”
▷ Actor model of Elixir/Erlang
▷ GenStage
13

14. GenStage
▷ behavior for exchanging events with
back-pressure between Elixir processes
▷ José Valim defined GenStage as “better
abstractions for working with collections”
▷ but we can use it for “better interprocess
communication”
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15. 2.
Flowex
Railway Flow-Based Programming
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16. Flowex
▷ a set of abstractions built on top Elixir
GenStage which allows writing
program with FBP paradigm
▷ a mix of FBP and Railway Oriented
Programming (ROP) approach
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17. Railway oriented programming
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18. Railway FBP
Let’s place each function inside
separate process
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19. use Flowex.Pipeline
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20. Functions’ definitions
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21. Control and evaluation
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Some new functions appear in the
FunPipeline module:
▷ “start” and “stop”
▷ “call” and “cast”

22. FunPipeline.start
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23. “call” and “cast” (sync and async)
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24. FunPipeline.call
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add_one
minus_three
mult_by_two
producer
consumer
number: 2
number: 2
number: 3
number: 6
number: 3number: 3
self()

25. “error_pipe”
If an error happens in some pipe, functions
in next pipes will not be called and IP will be
bypassed to the “error_pipe”
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26. Run pipeline via
Flowex.Client
▷ Use Clients for
parallel processing of
many IPs
▷ Allows effective using
of pipeline even with
synchronous “call”
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27. Fight bottlenecks
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28. “Controlled parallelism”
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29. Reusable components with
module pipes
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One should implement “init” and
“call” functions
(like in Elixir’s Plug library)

30. Advantages of Flowex approach
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▷ Explicit definition of:
- structure of data will be processed
- way the data will come
▷ Easy to maintain and reuse:
- predefined set of working processes
- components are isolated and reusable
▷ Controlled parallelism:
- one can control number of clients
supplying data
- one can control the number of processes
available for each component

31. 3.
Running external programs
Tools
31

32. Why do we need this?
▷ Elixir/Erlang ecosystem is not so big as
Java, Ruby, Python, etc.
▷ Elixir/Erlang is not the fastest platform
▷ There are not so many Elixir/Erlang
developers
32

33. Erlang ports
▷ provide a byte-oriented interface to an
external program over STDIN and STDOUT
▷ are process-specific resources - only owner
process can talk to external process
▷ are flexible, safe and allows error trapping
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34. ErlPort project
▷ helps connect Erlang to other
programming languages
▷ currently supported external languages
are Python and Ruby
▷ has Elixir wrapper - export
Read more on erlport.org
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35. Porcelain project
▷ helps launching and communicating with
external OS processes from Elixir
▷ launches external programs in a
synchronous or asynchronous manner
▷ implements multiple ways of passing input
to the program and getting back its output
Read more on alco/porcelain 35

36. 4.
Multi-language components
Example project
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https://github.com/antonmi/multi_flowex

37. MultiFlowex pipeline
▷ There will be Ruby, Python and shell “pipes”
▷ Each will say “Hello”
▷ The result will be:
“Hello from Ruby, Hello from Python, Hello
from shell”
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38. multi_flowex dependencies
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39. Ruby component
Demonstrates how one can create
components using Ruby, Python or Shell
Read more on ….
39

40. Ruby code in main.rb file
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41. Ruby component specs
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42. Python component
Demonstrates how one can create
components using Ruby, Python or Shell
Read more on ….
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43. Python code in main.py file
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44. Shell component
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45. The last, Elixir component
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46. MultiPipeline
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47. Pipeline starts external processes
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▷ 3 Ruby processes
▷ 4 Python processes

48. MultiPipeline specs
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49. Conclusion
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▷ FBP paradigm is an advantageous
alternative to “conventional programming”
▷ Flowex makes it easy to convert sequential
code into a pipeline of independent
components
▷ Erlang ports open new horizons,
so you can leverage the advantages of
other programming languages

50. Thanks!
Any questions?
50