Time and Concurrency

Presentation for Baltimore Innovation Week 2015 DevDay.
Original Reveal.js slides at http://decomplecting.org/time-and-concurrency

Transcript

1. TIME AND CONCURRENCY PROGRAMMING PARADIGMS AND THE FAILURE OF STATE Jason Lewis @canweriotnow Yet Analytics
2. HELLO I think I was destined to become a functional programmer.
3. Some years ago
4. I spraypainted liked graffiti like this...
5. ...and ended up here.
6. TIME WE HAVE PROBLEMS WITH: State Value Identity
7. You could not step twice into the same river. — Heraclitus of Ephesus
8. PROBLEMS ARE BOTH: In our programs In our datastores
9. THERE ARE SOLUTIONS Clojure Datomic (of which these are but two)
10. WHAT IS IT?
11. AN EXPERT EXPLAINS 0:18
12. TIME PERCEPTION
13. REALITY
14. CONCURRENCY Really, ( > = t h i n g s 3 ) Concurrency Parallellism Distributed systems ...
15. CONCURRENCY Object-Oriented (stateful): Stateful objects Mutexes and locking No (realistic) notion of time
17. Functional: Pure fns are timeless Zero state Run anywhen, anywhere, same result
19. CLOJURE(SCRIPT) Emphasis on pure functions Persistent data structures Side-effects are allowed State is managed
20. Web programming IS distributed systems programming.
21. Even in the simplest web application, we need to consider at least 3 things: the server, the browser, and the user.
22. One language, two hosts: JVM (server) JS (browser)
23. Code Sharing ( d e f n s t r - > i n t [ s ] # ? ( : c l j ( j a v a . l a n g . I n t e g e r / p a r s e I n t s ) : c l j s ( j s / p a r s e I n t s ) ) )
24. DATOMIC EAVT tuple store database. ACID transactions. Immutable data = strong consistency + horizontal read scalability. Writes are not update-in-place; all data is retained by default. Makes time part of the database itself.
25. BIG WIN: TIME TRAVEL
26. Since Datomic retains the history of the db state, we can query the db as-of any given point in time. Since it treats the db as a value, and uses the same persistent data structures as Clojure itself, we can also query the future, by joining arbitrary data to a given db value.
27. IT GETS BETTER... ( q ' [ : f i n d ? t i t l e : w h e r e [ ? e : m o v i e / y e a r 1 9 8 7 ] [ ? e : m o v i e / t i t l e ? t i t l e ] ] ) Datomic's datalog queries are just vectors, which means they can be passed around like any other of Clojure's persistent data structures... even from the browser to the server.
28. PUTTING IT ALL TOGETHER
30. Pure functions acting on immutable data structures shared between client and server. Peers keep a hot copy of the db as a value in memory Reads and writes are orthogonal
31. Time = λ
32. Baltimore Clojure Meetup http://is.gd/baltimoreclojure
33. THANK YOU! Jason Lewis Yet Analytics @canweriotnow jason@yetanalytics.com