Slide 1

Slide 1 text

C# Assíncrono Os segredos por trás de async e await Alex Tercete [email protected]

Slide 2

Slide 2 text

Assíncrono?

Slide 3

Slide 3 text

https://www.flickr.com/photos/snekse/2501155494

Slide 4

Slide 4 text

2 minutos 5 minutos

Slide 5

Slide 5 text

t

Slide 6

Slide 6 text

t

Slide 7

Slide 7 text

t

Slide 8

Slide 8 text

t 21 0

Slide 9

Slide 9 text

8 funcionários 12 clientes atendidos 21 minutos

Slide 10

Slide 10 text

Não funciona

Slide 11

Slide 11 text

t 21 0

Slide 12

Slide 12 text

t 21 0

Slide 13

Slide 13 text

t 21 0

Slide 14

Slide 14 text

t 21 0

Slide 15

Slide 15 text

8 funcionários 16 clientes atendidos 19 minutos

Slide 16

Slide 16 text

47% mais eficiente

Slide 17

Slide 17 text

Síncrono Assíncrono

Slide 18

Slide 18 text

C#

Slide 19

Slide 19 text

I/O Rede Banco de dados Sistema de arquivos Paralelismo

Slide 20

Slide 20 text

.NET 1.1+ APM public interface IAsynchronousProgrammingModel { IAsyncResult BeginSomething( AsyncCallback callback, object state); T EndSomething(IAsyncResult result); } https://gist.github.com/alextercete/f34691cb9e4df4d2e78b

Slide 21

Slide 21 text

.NET 1.1+ APM public class AsynchronousProgrammingModelWrapper { private readonly IAsynchronousProgrammingModel _apm; // Constructor public Task SomethingAsync() { return Task.Factory.FromAsync( _apm.BeginSomething, _apm.EndSomething, null); } } https://gist.github.com/alextercete/f34691cb9e4df4d2e78b

Slide 22

Slide 22 text

.NET 1.1+ APM public class AsynchronousProgrammingModelWrapper { private readonly IAsynchronousProgrammingModel _apm; // Constructor public Task SomethingAsync() { return Task.Factory.FromAsync( _apm.BeginSomething, _apm.EndSomething, null); } } https://gist.github.com/alextercete/f34691cb9e4df4d2e78b

Slide 23

Slide 23 text

.NET 4.0+ TPL public interface IDependency { Task BeforeAsync(); Task AfterAsync(object result); } https://gist.github.com/alextercete/a011bafde7187104303b

Slide 24

Slide 24 text

.NET 4.0+ TPL public interface IDependency { Task BeforeAsync(); Task AfterAsync(object result); } https://gist.github.com/alextercete/a011bafde7187104303b

Slide 25

Slide 25 text

.NET 4.0+ TPL public class TaskParallelLibrary { private readonly IDependency _dependency; // Constructor public Task SomethingAsync() { return _dependency.BeforeAsync().ContinueWith( previous => _dependency.AfterAsync(previous.Result) ).Unwrap(); } } https://gist.github.com/alextercete/a011bafde7187104303b

Slide 26

Slide 26 text

.NET 4.0+ TPL public class TaskParallelLibrary { private readonly IDependency _dependency; // Constructor public Task SomethingAsync() { return _dependency.BeforeAsync().ContinueWith( previous => _dependency.AfterAsync(previous.Result) ).Unwrap(); } } https://gist.github.com/alextercete/a011bafde7187104303b

Slide 27

Slide 27 text

.NET 4.5+ async/await public class TaskParallelLibrary { private readonly IDependency _dependency; // Constructor public async Task SomethingAsync() { var result = await _dependency.BeforeAsync(); return await _dependency.AfterAsync(result); } } https://gist.github.com/alextercete/a011bafde7187104303b

Slide 28

Slide 28 text

.NET 4.5+ async/await public class TaskParallelLibrary { private readonly IDependency _dependency; // Constructor public async Task SomethingAsync() { var result = await _dependency.BeforeAsync(); return await _dependency.AfterAsync(result); } } https://gist.github.com/alextercete/a011bafde7187104303b

Slide 29

Slide 29 text

Use async/await

Slide 30

Slide 30 text

Os 8 erros mais comuns O #5 vai fazer você se emocionar

Slide 31

Slide 31 text

public interface IDependency { Task BeforeAsync(); Task AfterAsync(object result); Task SomethingAsync(); Task SomethingAsync(CancellationToken token); Task SomethingAsync( Func> callback); } https://gist.github.com/alextercete/1acbaf93605383fcea51

Slide 32

Slide 32 text

#1 O código quase assíncrono

Slide 33

Slide 33 text

public class TheAlmostAsync { // Private fields and constructor public T Something() { return SomethingAsync().Result; } public async Task SomethingAsync() { var result = await _dependency.BeforeAsync(); return await _dependency.AfterAsync(result); } } https://gist.github.com/alextercete/1acbaf93605383fcea51

Slide 34

Slide 34 text

public class TheAlmostAsync { // Private fields and constructor public T Something() { return SomethingAsync().Result; } public async Task SomethingAsync() { var result = await _dependency.BeforeAsync(); return await _dependency.AfterAsync(result); } } https://gist.github.com/alextercete/1acbaf93605383fcea51

Slide 35

Slide 35 text

public class TheAlmostAsync { // Private fields and constructor public T Something() { return SomethingAsync().Result; } public async Task SomethingAsync() { var result = await _dependency.BeforeAsync(); return await _dependency.AfterAsync(result); } } https://gist.github.com/alextercete/1acbaf93605383fcea51

Slide 36

Slide 36 text

https://www.flickr.com/photos/justinjensen/4710621230

Slide 37

Slide 37 text

return SomethingAsync().Result; Something Thread x

Slide 38

Slide 38 text

return SomethingAsync().Result; Something Contexto Thread x

Slide 39

Slide 39 text

return SomethingAsync().Result; Something SomethingAsync var result = await _dependency.BeforeAsync(); return await _dependency.AfterAsync(result); Contexto Thread y Thread x

Slide 40

Slide 40 text

return SomethingAsync().Result; Something SomethingAsync var result = await _dependency.BeforeAsync(); return await _dependency.AfterAsync(result); Contexto Thread y Thread x

Slide 41

Slide 41 text

public class TheAlmostAsyncFixed { // Private fields and constructor public T Something() { return SomethingAsync().Result; } public async Task SomethingAsync() { var result = await _dependency.BeforeAsync().ConfigureAwait(false); return await _dependency.AfterAsync(result).ConfigureAwait(false); } } https://gist.github.com/alextercete/1acbaf93605383fcea51

Slide 42

Slide 42 text

Use .ConfigureAwait(false) em código de bibliotecas

Slide 43

Slide 43 text

#2 O código pseudo-assíncrono

Slide 44

Slide 44 text

public class ThePseudoAsync { public async Task SomethingAsync() { return default(T); } } https://gist.github.com/alextercete/1acbaf93605383fcea51

Slide 45

Slide 45 text

public class ThePseudoAsync { public async Task SomethingAsync() { return default(T); } } https://gist.github.com/alextercete/1acbaf93605383fcea51

Slide 46

Slide 46 text

Síncrono até encontrar o primeiro ponto de assincronia

Slide 47

Slide 47 text

#3 O código super-assíncrono

Slide 48

Slide 48 text

public class TheSuperAsync { // Private fields and constructor public async Task SomethingAsync() { return await _dependency.SomethingAsync( async result => await _dependency.AfterAsync(result)); } } https://gist.github.com/alextercete/1acbaf93605383fcea51

Slide 49

Slide 49 text

public class TheSuperAsync { // Private fields and constructor public async Task SomethingAsync() { return await _dependency.SomethingAsync( async result => await _dependency.AfterAsync(result)); } } https://gist.github.com/alextercete/1acbaf93605383fcea51

Slide 50

Slide 50 text

public class TheSuperAsync { // Private fields and constructor public async Task SomethingAsync() { return await _dependency.SomethingAsync( async result => await _dependency.AfterAsync(result)); } } https://gist.github.com/alextercete/1acbaf93605383fcea51

Slide 51

Slide 51 text

public class TheSuperAsyncFixed { // Private fields and constructor public Task SomethingAsync() { return _dependency.SomethingAsync( result => _dependency.AfterAsync(result)); } } https://gist.github.com/alextercete/1acbaf93605383fcea51

Slide 52

Slide 52 text

Evite async/await quando não for necessário

Slide 53

Slide 53 text

#4 O retorno nulo

Slide 54

Slide 54 text

public class TheNullReturn { // Private fields and constructor public Task AfterAsync(object result) { if (result == null) return null; return _dependency.AfterAsync(result); } } https://gist.github.com/alextercete/1acbaf93605383fcea51

Slide 55

Slide 55 text

public class TheNullReturn { // Private fields and constructor public Task AfterAsync(object result) { if (result == null) return null; return _dependency.AfterAsync(result); } } https://gist.github.com/alextercete/1acbaf93605383fcea51

Slide 56

Slide 56 text

public class TheNullReturnFixed where T : class { // Private fields and constructor public Task AfterAsync(object result) { if (result == null) return Task.FromResult(null); return _dependency.AfterAsync(result); } } https://gist.github.com/alextercete/1acbaf93605383fcea51

Slide 57

Slide 57 text

#5 O contexto perdido

Slide 58

Slide 58 text

Verifique se isso está em seu Web.config

Slide 59

Slide 59 text

OU

Slide 60

Slide 60 text

public class TheMissingContext { // Private fields and constructor public async Task SomethingAsync() { var result = await _dependency.BeforeAsync() .ConfigureAwait(false); // HttpContext.Current == null return await _dependency.AfterAsync(result) .ConfigureAwait(false); } } https://gist.github.com/alextercete/1acbaf93605383fcea51

Slide 61

Slide 61 text

public class TheMissingContextFixed { // Private fields and constructor public async Task SomethingAsync() { var context = HttpContext.Current; var result = await _dependency.BeforeAsync() .ConfigureAwait(false); HttpContext.Current = context; return await _dependency.AfterAsync(result) .ConfigureAwait(false); } } https://gist.github.com/alextercete/1acbaf93605383fcea51

Slide 62

Slide 62 text

#6 A chamada esquecida

Slide 63

Slide 63 text

public class TheForgottenCall { // Private fields and constructor public Task SomethingAsync() { SomethingNotAsync(); return CompletedTask; } private async void SomethingNotAsync() { await _dependency.BeforeAsync(); } } https://gist.github.com/alextercete/1acbaf93605383fcea51

Slide 64

Slide 64 text

https://gist.github.com/alextercete/1acbaf93605383fcea51 public class TheForgottenCall { // Private fields and constructor public Task SomethingAsync() { SomethingNotAsync(); return CompletedTask; } private async void SomethingNotAsync() { await _dependency.BeforeAsync(); } } private static Task CompletedTask { get { return Task.FromResult(0); } }

Slide 65

Slide 65 text

public class TheForgottenCall { // Private fields and constructor public Task SomethingAsync() { SomethingNotAsync(); return CompletedTask; } private async void SomethingNotAsync() { await _dependency.BeforeAsync(); } } https://gist.github.com/alextercete/1acbaf93605383fcea51

Slide 66

Slide 66 text

public class TheForgottenCallFixed { // Private fields and constructor public async Task SomethingAsync() { await SomethingNowAsync(); } private async Task SomethingNowAsync() { await _dependency.BeforeAsync(); } } https://gist.github.com/alextercete/1acbaf93605383fcea51

Slide 67

Slide 67 text

Nunca use async void

Slide 68

Slide 68 text

public class TheForgottenCall { // Private fields and constructor public Task AfterAsync(object result) { _dependency.AfterAsync(result); return CompletedTask; } } https://gist.github.com/alextercete/1acbaf93605383fcea51

Slide 69

Slide 69 text

public class TheForgottenCall { // Private fields and constructor public Task AfterAsync(object result) { _dependency.AfterAsync(result); return CompletedTask; } } https://gist.github.com/alextercete/1acbaf93605383fcea51

Slide 70

Slide 70 text

public class TheForgottenCallFixed { // Private fields and constructor public async Task AfterAsync(object result) { await _dependency.AfterAsync(result); } } https://gist.github.com/alextercete/1acbaf93605383fcea51

Slide 71

Slide 71 text

public class TheForgottenCallReallyFixed { // Private fields and constructor public Task AfterAsync(object result) { return _dependency.AfterAsync(result); } } https://gist.github.com/alextercete/1acbaf93605383fcea51

Slide 72

Slide 72 text

#7 O cancelamento ignorado

Slide 73

Slide 73 text

public class TheIgnoredCancellation { // Private fields and constructor public Task SomethingAsync(CancellationToken token) { return _dependency.SomethingAsync(); } } https://gist.github.com/alextercete/1acbaf93605383fcea51

Slide 74

Slide 74 text

public class TheIgnoredCancellation { // Private fields and constructor public Task SomethingAsync(CancellationToken token) { return _dependency.SomethingAsync(); } } https://gist.github.com/alextercete/1acbaf93605383fcea51

Slide 75

Slide 75 text

public class TheIgnoredCancellationFixed { // Private fields and constructor public Task SomethingAsync(CancellationToken token) { return _dependency.SomethingAsync(token); } } https://gist.github.com/alextercete/1acbaf93605383fcea51

Slide 76

Slide 76 text

O cancelamento depende de quem observa o token

Slide 77

Slide 77 text

#8 A disputa pelas threads

Slide 78

Slide 78 text

public class TheThreadsDispute { // Private fields and constructor public T Something() { return Task.Run(() => _dependency.SomethingAsync()).Result; } public IList Somethings(int count) { var results = new List(count); Parallel.For(0, count, i => results[i] = _dependency.SomethingAsync().Result); return results; } } https://gist.github.com/alextercete/1acbaf93605383fcea51

Slide 79

Slide 79 text

public class TheThreadsDispute { // Private fields and constructor public T Something() { return Task.Run(() => _dependency.SomethingAsync()).Result; } public IList Somethings(int count) { var results = new List(count); Parallel.For(0, count, i => results[i] = _dependency.SomethingAsync().Result); return results; } } https://gist.github.com/alextercete/1acbaf93605383fcea51

Slide 80

Slide 80 text

public class TheThreadsDispute { // Private fields and constructor public T Something() { return Task.Run(() => _dependency.SomethingAsync()).Result; } public IList Somethings(int count) { var results = new List(count); Parallel.For(0, count, i => results[i] = _dependency.SomethingAsync().Result); return results; } } https://gist.github.com/alextercete/1acbaf93605383fcea51

Slide 81

Slide 81 text

https://www.flickr.com/photos/eustaquio/10556254584

Slide 82

Slide 82 text

Thread Pool Requests Queue

Slide 83

Slide 83 text

Thread Pool Requests Queue

Slide 84

Slide 84 text

Thread Pool Requests Queue

Slide 85

Slide 85 text

Thread Pool Requests Queue

Slide 86

Slide 86 text

Thread Pool Requests Queue

Slide 87

Slide 87 text

Thread Pool Requests Queue

Slide 88

Slide 88 text

Thread Pool Requests Queue

Slide 89

Slide 89 text

Thread Pool Requests Queue

Slide 90

Slide 90 text

Thread Pool Requests Queue

Slide 91

Slide 91 text

Thread Pool Requests Queue

Slide 92

Slide 92 text

Thread Pool Requests Queue

Slide 93

Slide 93 text

Thread Pool Requests Queue

Slide 94

Slide 94 text

Thread Pool Requests Queue

Slide 95

Slide 95 text

Em cenários de alta concorrência, economize threads

Slide 96

Slide 96 text

public class TheThreadsDisputeFixed { // Private fields and constructor public T Something() { return _dependency.SomethingAsync().Result; } public IList Somethings(int count) { var results = new List(count); Parallel.For(0, count, i => results[i] = _dependency.SomethingAsync().Result); return results; } } https://gist.github.com/alextercete/1acbaf93605383fcea51

Slide 97

Slide 97 text

public class TheThreadsDisputeFixed { // Private fields and constructor public T Something() { return _dependency.SomethingAsync().Result; } public IList Somethings(int count) { var tasks = Enumerable.Range(0, count).Select( i => _dependency.SomethingAsync()); return Task.WhenAll(tasks).Result; } } https://gist.github.com/alextercete/1acbaf93605383fcea51

Slide 98

Slide 98 text

public class TheThreadsDisputeReallyFixed { // Private fields and constructor public Task SomethingAsync() { return _dependency.SomethingAsync(); } public async Task> SomethingsAsync(int count) { var tasks = Enumerable.Range(0, count).Select( i => _dependency.SomethingAsync()); return await Task.WhenAll(tasks); } } https://gist.github.com/alextercete/1acbaf93605383fcea51

Slide 99

Slide 99 text

https://www.flickr.com/photos/eschipul/4160817135

Slide 100

Slide 100 text

https://www.flickr.com/photos/22897666@N00/6883636817

Slide 101

Slide 101 text

3 minutos 15 segundos

Slide 102

Slide 102 text

Se a espera for pequena, a troca de contexto não compensa

Slide 103

Slide 103 text

1 minuto 10 minutos

Slide 104

Slide 104 text

21 0 t

Slide 105

Slide 105 text

21 0 t

Slide 106

Slide 106 text

Sempre haverá um gargalo

Slide 107

Slide 107 text

5 minutos 3 minutos

Slide 108

Slide 108 text

21 0 t

Slide 109

Slide 109 text

21 0 t

Slide 110

Slide 110 text

http://commons.wikimedia.org/wiki/File:Israel_Austerity.jpg

Slide 111

Slide 111 text

Se a fila estiver grande, os clientes irão embora

Slide 112

Slide 112 text

Dúvidas?

Slide 113

Slide 113 text

Obrigado! Alex Tercete [email protected]

Slide 114

Slide 114 text

Referências Blogs: – http://blogs.msdn.com/b/pfxteam/ – http://blog.stephencleary.com/ Talks: – The zen of async: Best practices for best performance – Async'ing Your Way to a Successful App with .NET – Async in ASP.NET

Slide 115

Slide 115 text

Créditos – http://thenounproject.com/term/cash-register/41958/ – http://thenounproject.com/term/lunch/62503/ – http://thenounproject.com/term/server/33544/ – http://thenounproject.com/term/server/32430/ – http://thenounproject.com/term/server/32429/ – http://thenounproject.com/term/server/32431/ – http://thenounproject.com/term/lock/5427/ – http://thenounproject.com/term/hour-glass/16705/ – http://thenounproject.com/term/money/27047/ – http://thenounproject.com/term/printer/1235/