5. Concurrency != Parallelism
•
•
•
Concurrency is a model for concurrent
execution.
Parallelism is the literal act of being
concurrent.
With concurrency, tasks are able to run at the same
time,
but they don’t have to — that’s
parallelism.
6. CSP: Huh?
•
A formal language for describing patterns of
interaction in concurrent systems.
•
based on message passing via channels.
7. Channels
•
A powerful primitive for communication
•
Channels are exactly what you think it is; they let you pass stuff
through it.
•
Two basic actions: Put & Take
Input
Channel
Output
9. Basic Actions
•
Put: Send a new value onto the channel
•
Take: Receive on existing value from the channel.
10. Channel Semantics
•
Semantics vary on the language/implementation.
•
The basic semantics are:
•
on share-ability of concrete channels. (i.e., across
tasks/threads?)
•
when channels block
11. Blocking
•
Can block when trying to put a value onto the
channel when it’s full.
•
Can block when trying to take a value from an
empty channel.
12. What Blocks?
•
Very much dependent on the implementation/language.
•
Golang blocks on goroutines (a.k.a green threads)
•
Rust blocks on tasks (a.k.a green threads or native
threads)
•
Clojure (core.async): both actions have the potential
to block the underlying thread.
13. Clojure: core.async
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A library not a language feature.
•
Goes to show how powerful a consistent language form (Lisp)
can be, thanks to macros.
•
Supports unbounded buffered and bounded buffered
channels. The former is discouraged.
•
Two implementations of the underlying “threads”.
•
Supports timeouts (super powerful)
•
All operations are expressions not statements.
•
Priority selects with alts!
14. Clojure: core.async
•
Supports two kinds of thread of control:
•
•
•
IoC (inversion of control)
Normal Threads
IoC threads are created with go blocks
•
go is a macro that examines it’s body for any
channel operations and turns them into a state
machine.
•
C#’s async does the same thing.
17. Callbacks (Direct Data-Flow)
•
Worst style of concurrency
•
You have no control over the data flow.
•
You’re (the callback) at the mercy of the caller.
19. Indirect = Channels
•
Channels offer a better alternative at managing
data-flow.
•
They are indirect. This means the logic is in control
of the data-flow.
•
The logic can decide when it’s had too much data
coming through. It’s the best decider at judging how
much it can handle.
20. Examples!
•
Return the 5 fastest search queries.
•
Return the x number of queries that finish within 3
seconds (timeouts)
•
Channels act like queues. They’re a buffer for your
data.
22. Components
•
Not an abstract component.
•
https://github.com/component/component
•
A client-side package manager and build tool.
•
CommonJS style code.
•
Ability to share client and server code super easily.
23. Unix Style
•
Build small, concentrated applications that do one
thing, and does that thing extremely well.
•
Modular
•
Modular
•
Modular
24. Globals..grrr
•
Globals are horrible. Never use them.
•
Globals are horrible. Never use them.
•
Globals are horrible. Never use them.
•
jQuery, Angular, Ember, etc… ALL use them.
25. /**
* Module Dependencies
*/
var dom = require('dom');
var model = require('tower-model');
var migration = require('tower-migration');
/**
* User Model
*/
model('user')
.attr('email')
.validate('presence')
.validate('isEmail')
.attr('firstname')
.attr('lastname')
.attr('country')
.attr('city');
/**
* Migration
*/
migration.up('create_user_table')
.model('user');
27. Modular Apps
•
It’s the future
•
Building monolithic apps suck
•
Tooling is only going to get better.
•
It’s much easier to wrap your head around a single
module that has no side-effects (i.e., no external
state & globals).
28. Server & Client-side
•
Node.js offers the ability to share code with the
client-side (components).
•
Both have the same module pattern (CommonJS
•
Module can now be designed for both platforms.
29. No Globals?
•
We can take advantage of the module caching.
•
A version of inversion-of-control
•
Decentralized.
30. Module Caching
•
If each module is concentrated, you can store data (instances,
values, etc…) in the module exports or module itself.
•
Example!
31. Wrapping Up
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CSP is awesome.
•
Clojure is awesome.
•
Message passing & channels are awesome.
•
Modular apps are awesome.
•
Globals are horrible.
•
Callbacks are horrible.
