Exploring Processes and OTP behaviours in Erlang

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Exploring Processes and OTP behaviours in 17 ottobre Erlang - Elixir meetup Bologna

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@pdincau

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Funzionale General purpose Dinamico Concorrente Garbage collected - 1 - Erlang Run-Time System Ideato da Ericsson per la necessità di Business reali

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Soluzione ai problemi odierni e futuri Programmare diversamente - 2 - PERCHÈ USARLO?

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“If we want to write programs that behave as other objects behave in the real world, then these programs will have a concurrent structure. Use a language that was designed for writing concurrent applications, and development becomes a lot easier. Erlang programs model how we think and interact.” Joe Armstrong Programming Erlang - 1st Edition - 3 -

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- 4 - Moduli o Classi “It’s OO, but pretend it isn’t, please” Fred Hebert Joe Armstrong / Ralph Johnson infoq.com/interviews/johnson-armstrong-oop ferd.ca/an-open-letter-to-the-erlang-beginner-or-onlooker.html VENITE DAL MONDO OOP?

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- 5 - Actor Model TASK = fun(message) http:/ /learnyousomeerlang.com/the-hitchhikers-guide-to-concurrency LA REALTÀ

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- 6 - Green Threads e message passing - 6 - - 6 - PROCESSI

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- 7 - UN ESEMPIO PRATICO?

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- 8 - P1 P2 P2 ! {increment, N} COUNTER SERVER

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- 9 - COUNTER CODICE

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P1 P2 P2 ! {self(), {increment, N}} - 10 - P1 ! {Pid2, Result} CHIAMATA SINCRONA

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- 11 - COUNTER MIGLIORATO

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P1 P2 m1 P3 P4 P5 m2 m3 m4 - 12 - COUNTERS

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- xx - PROVIAMO!

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P1 P2 P3 P4 - 13 - CRASH!

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- 14 - PRIMITIVE DI ERLANG spawn link spawn_link monitor

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NON COSÌ - 15 -

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{'EXIT', From, Reason} crash! crash! crash! - 16 - CRASH! CRASH! CHRASH! P1 P2 P3 P4

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trap_exit - 17 -

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“…OTP, the 800-pound gorilla of process architecture” Dave Thomas Programming Elixir - 18 -

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Librerie con pattern comuni che ci consentono di sviluppare applicazioni: - xx - DISTRIBUITE e FAULT TOLERANT - 18 -

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- 19 - Modella il server di una relazione di tipo client-server Server Client Client Client Query Reply http:/ /www.erlang.org/doc/design_principles/gen_server_concepts.html GEN_SERVER

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- 20 - GEN_SERVER

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- 21 - GEN_SERVER

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- 22 - State(S) x Event(E) -> Actions(A), State(S') Lobby Idle Disconnected Reconnected timeout Stop GEN_FSM

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Wander Pursue Act Eat Act Act Act Act Act Act - 23 - GEN_FSM

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- 24 - GEN_EVENT server event manager g(event) f(event) h(event) event “Proﬁling and Debugging Erlang Systems” Martin Kjellin, Roberto Aloi youtube.com/watch?v=4u6c2FNauYE

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- 25 - SUPERVISOR Main Sup. GCM 2 GCM 1 Il cuore della afﬁdabilità di Erlang

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- 26 - SUPERVISOR Sup. Main Sup. Seq. Worker Stash Worker “OTP: Supervisors” Programming Elixir Dave Thomas

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- 27 - APPLICATION Raccoglie codice comune a una funzionalità start/stop Organizzazione dei ﬁle Gestione delle conﬁgurazioni Riutilizzabile

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- 28 - RELEASE Una "release" è un insieme di applicazioni Erlang deployate ed eseguite assieme rebar3 è un grande passo avanti Gestione conﬁgurazioni

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- 29 - Erlang in production: "I wish I'd known that when I started" Bernard Duggan youtube.com/watch?v=G0eBDWigORY Thinking like an Erlanger Torben Hoffmann youtube.com/watch?v=_fgaPGLGZI0 RISORSE UTILI

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Grazie