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Elixir Peeking into Elixir’s Processes, OTP & Supervisors 21st March 2014 /benjamintanweihao /bentanweihao [email protected]

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What will we learn today? Elixir & Erlang In less than 5 minutes

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Elixir & Erlang In less than 5 minutes Processes 101 The Basic Concurrency Primitive What will we learn today?

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Elixir & Erlang In less than 5 minutes OTP Framework and much more Processes 101 The Basic Concurrency Primitive What will we learn today?

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Elixir & Erlang In less than 5 minutes OTP Framework and much more Supervisors Fault Tolerance & Recovery Processes 101 The Basic Concurrency Primitive What will we learn today?

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Ohai, Elixir!

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Elixir & Erlang In less than 5 minutes

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Ohai, Erlang! Erlang is a general-purpose concurrent, garbage-collected programming language and runtime system. The sequential subset of Erlang is a functional language, with eager evaluation, single assignment, and dynamic typing. It was designed by Ericsson to support distributed, fault-tolerant, soft-real-time, non- stop applications. It supports hot swapping, so that code can be changed without stopping a system.

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Ohai, Erlang! Erlang is a general-purpose concurrent, garbage-collected programming language and runtime system. The sequential subset of Erlang is a functional language, with eager evaluation, single assignment, and dynamic typing. It was designed by Ericsson to support distributed, fault-tolerant, soft-real-time, non- stop applications. It supports hot swapping, so that code can be changed without stopping a system.

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• Free lunch is over Why Elixir ?

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Why Elixir ? • Free lunch is over • Hyper-threading & Multicore • Faster software means using all cores! • But … Concurrency -> Coordination • Functional makes this easier

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Design Goals of Elixir 1.Productivity 2.Extensibility 3.Compatibility

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Productivity Complete Elixir Application

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Productivity Includes Supervisor Chain

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Productivity Testing built-in

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Extensibility Macros & Meta-programming Implementing unless using if

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Extensibility Macros & Meta-programming Implementing unless using if

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Compatibility Elixir can call Erlang code, without any conversion cost at all.

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Compatibility Elixir can use Erlang libraries!

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The Actor Concurrency Model • Actor = Process

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The Actor Concurrency Model • Actor = Process • A process performs a specific task when it receives a message

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The Actor Concurrency Model • Actor = Process • A process performs a specific task when it receives a message • In turn, the process can reply to the sender

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The Actor Concurrency Model • Actor = Process • A process performs a specific task when it receives a message • In turn, the process can reply to the sender • All messages go to a processes’ mailbox – Q of unprocessed messages sent from other processes that are not yet consumed

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The Actor Concurrency Model • Actor = Process • A process performs a specific task when it receives a message • In turn, the process can reply to the sender • All messages go to a processes’ mailbox – Q of unprocessed messages sent from other processes that are not yet consumed Shared-nothing Async Message-passing

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Processes 101 The Basic Concurrency Primitive

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Creating Processes & Sending Messages in Elixir Creating a Process

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Creating Processes & Sending Messages in Elixir Module, Function, Arguments

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Creating Processes & Sending Messages in Elixir Process id

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Creating Processes & Sending Messages in Elixir Sending a Message to w1

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Creating Processes & Sending Messages in Elixir Process waits for a message …

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Creating Processes & Sending Messages in Elixir Pattern matches!

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Creating Processes & Sending Messages in Elixir Result is sent back to the calling process (self)

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Creating Processes & Sending Messages in Elixir Returns immediately

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Creating Processes & Sending Messages in Elixir Get result from self

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Creating Processes & Sending Messages in Elixir Demo

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OTP Framework and much more

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What is OTP? • Comes with Elixir/Erlang • Framework to build applications that are fault- tolerant, scalable, distributed • Databases + Profilers + Debuggers

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OTP Behaviours • GenServer • Supervisor • Application

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An Example GenServer Implement the GenServer Behaviour

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An Example GenServer Implement GenServer Callbacks

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An Example GenServer Callbacks are NOT called explicitly

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An Example GenServer OTP calls the callbacks.

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An Example GenServer Synchronous Call: Caller waits for reply

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An Example GenServer Asynchronous Call: Caller doesn’t wait for reply

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An Example GenServer Demo

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Supervisors Fault Tolerance & Recovery

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Supervisors for Fault Tolerance and Recovery one_for_one restart strategy

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Supervisors for Fault Tolerance and Recovery rest_for_all restart strategy

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Supervisors for Fault Tolerance and Recovery rest_for_one restart strategy

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An Example Supervisor Implement the Supervisor Behaviour

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An Example Supervisor Declaring the Supervision tree. Both Supervisors and Workers (e.g. GenServers) can be supervised.

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An Example Supervisor

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An Example Supervisor Declare the restart strategy

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Supervisor Demo Supervisor A Supervisor B Supervisor C Supervisor D Server D Server B Worker 1 Worker 1 Worker

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Supervisor Demo Supervisor A Supervisor B Supervisor C Supervisor D Server D Server B Worker 1 Worker 1 Worker one_for_one

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Supervisor Demo Supervisor A Supervisor B Supervisor C Supervisor D Server D Server B Worker 1 Worker 1 Worker one_for_all

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Supervisor Demo Supervisor A Supervisor B Supervisor C Supervisor D Server D Server B Worker 1 Worker 1 Worker simple_one_for_one

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Supervisor Demo Supervisor A Supervisor B Supervisor C Supervisor D Server D Server B Worker 1 Worker 1 Worker one_for_one

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Supervisor Demo Supervisor A Supervisor B Supervisor C Supervisor D Server D Server B Worker 1 Worker 1 Worker one_for_one simple_one_for_one one_for_all one_for_one

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Elixir & Erlang In less than 5 minutes OTP Framework and much more Supervisors Fault Tolerance & Recovery Processes 101 The Basic Concurrency Primitive

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Resources

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Work in Progress! ! Sign up at: http://www.exotpbook.com Me.

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Stickers!* *Very Limited Quantity

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Thanks! /benjamintanweihao /bentanweihao [email protected]