Recurring Tasks in Elixir

The problem: I want to email myself a weekly summary of Todo items I've completed. We know how to use cron or a variation of Ruby's Resque/Sidekiq scheduled jobs, but how would we approach this in Elixir?

We'll walk through a 40-line solution using a GenServer that will leave you wondering why we ever put up with installing an entire background job system for such a simple task.

Transcript

1. Recurring Tasks in Elixir Desmond Bowe NYC Elixir Meetup 6/15/2016
3. The Problem • I want to send emails every week
4. The Problem
5. Traditional Solutions • cron • Resque Scheduler/Sidekiq-cron
6. cron
7. cron
8. cron • PRO • everywhere
9. cron • PRO • everywhere • ???
10. cron • PRO • everywhere • ??? • CON • crontab -l
11. cron • PRO • everywhere • ??? • CON • crontab -l • 00 09-18 * * 1-5 /usr/bin/my-sweet-script
12. cron • PRO • everywhere • ??? • CON • crontab -l • 00 09-18 * * 1-5 /usr/bin/my-sweet-script
13. cron • PRO • everywhere • ??? • CON • crontab -l • 00 09-18 * * 1-5 /usr/bin/my-sweet-script
14. cron • PRO • everywhere • ??? • CON • crontab -l • 00 09-18 * * 1-5 /usr/bin/my-sweet-script • weird environment rules
15. cron • PRO • everywhere • ??? • CON • crontab -l • 00 09-18 * * 1-5 /usr/bin/my-sweet-script • weird environment rules not a big deal on Heroku
16. Resque/Sidekiq • PRO • CON
17. Resque/Sidekiq • PRO • reasonable syntax • access to your app • CON
18. Resque/Sidekiq • PRO • reasonable syntax • access to your app • CON • 1,000s of lines of code • requires external database • requires extra copy of app
19. Elixir
20. Elixir GenServers!
21. GenServer <look at some code>
22. GenServer
23. GenServer
24. GenServer • PRO • lightweight (~40 LOC) • doesn’t require separate app instance • leverages familiar Timex functionality • does not require additional database • can call any function in your app • CON
25. GenServer • PRO • lightweight (~40 LOC) • doesn’t require separate app instance • leverages familiar Timex functionality • does not require additional database • can call any function in your app • CON • …
26. GenServer • PRO • lightweight (~40 LOC) • doesn’t require separate app instance • leverages familiar Timex functionality • does not require additional database • can call any function in your app • CON • no built-in syntax for complex recurrence
27. GenServer
28. GenServer Other Thoughts • different schedules for users • use individual GenServers • have job requeue itself for next interval • expose the timer to read/cancel/update
29. thanks!