A Chat About Erlang - Speaker Deck

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A Chat About Erlang Bryce Kerley Miami Ruby Brigade February 18, 2013 Monday, February 18, 13

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Administrativia Please check on on the Meetup iPhone or Android app. Monday, February 18, 13

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Who Am I? Consulting Engineer Basho Technologies [email protected] @bonzoesc Monday, February 18, 13

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Disclaimer The thoughts, views, and opinions in this presentation are mine, and not my employer’s. Monday, February 18, 13

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Hello World io:format("Hello World\n"). Monday, February 18, 13

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What is Erlang? Functional Distributed Reliable Monday, February 18, 13

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1> X = 5. 5 2> Y = X. 5 3> 5 = Y. 5 4> Y = 6. ** exception error: no match Erlang is Functional Monday, February 18, 13

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5 3> 5 = Y. 5 4> Y = 6. ** exception error: no match 5> Z = fun(N) -> N * 2 end. #Fun 6> Z. #Fun 7> Z(5). 10 Erlang is Functional Monday, February 18, 13

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Erlang is Distributed > ./bin/riak attach Attaching to riak_ee-1.2.1rc2/dev/dev1 (^D to exit) ([email protected])1> nodes(). ['[email protected]','[email protected]','[email protected]', '[email protected]','[email protected]'] Monday, February 18, 13

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Erlang is Reliable Illustration by Fred Hébert, from “Learn You Some Erlang for Great Good!” Monday, February 18, 13

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Monday, February 18, 13

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What is Erlang? Functional Distributed Reliable Monday, February 18, 13

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What is Ruby? Object-Oriented Functional Rich Syntax Flexible Monday, February 18, 13

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What is Ruby bad at? Multitasking Garbage collection Predictability Monday, February 18, 13

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What is Erlang good at? Multitasking Garbage collection Predictability Monday, February 18, 13

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Hello World io:format("Hello World\n"). Monday, February 18, 13

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Hello World io:format("Hello World\n"). module Monday, February 18, 13

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Hello World io:format("Hello World\n"). module function Monday, February 18, 13

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Hello World io:format("Hello World\n"). module function string Monday, February 18, 13

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Hello World io:format("Hello World\n"). module function string newline Monday, February 18, 13

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Hello World io:format("Hello World\n"). module function string newline end statement Monday, February 18, 13

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Syntax handle_event(_Event, _StateName, StateData) -‐> {stop,badmsg,StateData}. https://github.com/basho/riak_kv/blob/53b343/src/riak_kv_get_fsm.erl#L289-L291 Monday, February 18, 13

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Syntax handle_event(_Event, _StateName, StateData) -‐> {stop,badmsg,StateData}. https://github.com/basho/riak_kv/blob/53b343/src/riak_kv_get_fsm.erl#L289-L291 function Monday, February 18, 13

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Syntax handle_event(_Event, _StateName, StateData) -‐> {stop,badmsg,StateData}. https://github.com/basho/riak_kv/blob/53b343/src/riak_kv_get_fsm.erl#L289-L291 function arguments Monday, February 18, 13

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Pattern Matching More useful than equality More powerful than method overloading describe_error(Desc, [], [trashed]) -‐> {obserror, Desc}; describe_error(Desc, [], Stack) -‐> {obserror, format("~s. Stack ~w", [Desc, Stack])}; describe_error(Desc, Rest, Stack) -‐> {obserror, format("~s. Rest: ~w Stack ~w", [Desc, Rest, Stack])}. Monday, February 18, 13

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Data Types •List •Tuple •Integer •Float •Atom (symbol) •Bit String Monday, February 18, 13

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Data Types •Fun: anonymous function, closure •Reference: unique ID •Port identiﬁer: pointer to an I/O port •Pid: pointer to an Erlang process Monday, February 18, 13

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Synthetic Data Types •Binary: a Bit String with a multiple of 8 bits •String: a List of Integers •Record: a Tuple enforced by the compiler •IO List: a List of Integers, Binaries, and IO Lists; or a Binary •Boolean: the atoms true and false Monday, February 18, 13

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Environment •Process: similar to a thread •Module: collection of functions •Macro: preprocessor facility (like C) Monday, February 18, 13

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Process Monday, February 18, 13

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Process •No shared memory Monday, February 18, 13

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Process •No shared memory •Asynchronous messaging Monday, February 18, 13

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Process •No shared memory •Asynchronous messaging •Garbage collected independently Monday, February 18, 13

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Process •No shared memory •Asynchronous messaging •Garbage collected independently •Fast to create, fast to destroy Monday, February 18, 13

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Process •No shared memory •Asynchronous messaging •Garbage collected independently •Fast to create, fast to destroy •Low overhead Monday, February 18, 13

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Open Telecom Platform Illustration by Fred Hébert, from “Learn You Some Erlang for Great Good!” Monday, February 18, 13

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Behaviors Similar to Ruby mixins Think Enumerable You implement callbacks Behavior supplies the rest Monday, February 18, 13

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gen_server Generic server Has state Takes synchronous calls, returns responses Takes asynchronous casts Monday, February 18, 13

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gen_server You Write It Does init turns arguments into state handle_call synchronous, respond and new state handle_cast asynchronous, new state handle_info timeout, new state terminate clean up code_change just upgraded, new state Monday, February 18, 13

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gen_server State: whatever you want Last argument Last element in response tuple handle_call(all_vnodes_status, _From, State) -‐> Reply = get_all_vnodes_status(State), {reply, Reply, State}; https://github.com/basho/riak_core/blob/1276e4e926b7007262f7631a27cdb4ecf6cbcaaf/src/riak_core_vnode_manager.erl#L260-L262 Monday, February 18, 13

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Other Behaviors gen_fsm: ﬁnite state machine gen_event: event dispatch and handling supervisor: keep trees of servers, fsms, events, etc. alive Monday, February 18, 13

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rebar Think Rake Generate scaffolds Run build tasks Monday, February 18, 13

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Riak Open-source database Built with Erlang, OTP, rebar, webmachine Great for sanity checking implementation Monday, February 18, 13

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riak_core Distributed system framework powering Riak Nice starting point Monday, February 18, 13

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What is Erlang bad at? Prolog syntax Opinionated rules No Rails-tier web frameworks Monday, February 18, 13

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What is Ruby good at? Friendly syntax Few rules, lots of customizability Great frameworks Monday, February 18, 13

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Should I Use Erlang? Monday, February 18, 13

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Should I Use Erlang? Yes* Monday, February 18, 13

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Should I Use Erlang? Yes* *If it makes sense Monday, February 18, 13

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Use Cases Social network Real-time chat Code sharing site Monday, February 18, 13

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Learn You Some Erlang http://learnyousomeerlang.com http://nostarch.com/erlang Monday, February 18, 13

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Links http://bit.ly/erlang-miamirb http://erlang.org/ http://learnyousomeerlang.com/ https://github.com/basho/rebar/ https://github.com/basho/rebar_riak_core/ Monday, February 18, 13