CSharp Assíncrono

Apresentação realizada como parte da iniciativa VTEX Tech Talks.
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Presentation made as a part of the VTEX Tech Talks initiative.

Transcript

1. C# Assíncrono Os segredos por trás de async e await Alex Tercete tercete@vtex.com.br
2. Assíncrono?
3. https://www.flickr.com/photos/snekse/2501155494
4. 2 minutos 5 minutos
5. t
6. t
7. t
8. t 21 0
9. 8 funcionários 12 clientes atendidos 21 minutos
10. Não funciona
11. t 21 0
12. t 21 0
13. t 21 0
14. t 21 0
15. 8 funcionários 16 clientes atendidos 19 minutos
16. 47% mais eficiente
17. Síncrono Assíncrono
18. C#
19. I/O Rede Banco de dados Sistema de arquivos Paralelismo
20. .NET 1.1+ APM public interface IAsynchronousProgrammingModel<T> { IAsyncResult BeginSomething( AsyncCallback callback, object state); T EndSomething(IAsyncResult result); } https://gist.github.com/alextercete/f34691cb9e4df4d2e78b
21. .NET 1.1+ APM public class AsynchronousProgrammingModelWrapper<T> { private readonly IAsynchronousProgrammingModel<T> _apm; // Constructor public Task<T> SomethingAsync() { return Task.Factory.FromAsync<T>( _apm.BeginSomething, _apm.EndSomething, null); } } https://gist.github.com/alextercete/f34691cb9e4df4d2e78b
22. .NET 1.1+ APM public class AsynchronousProgrammingModelWrapper<T> { private readonly IAsynchronousProgrammingModel<T> _apm; // Constructor public Task<T> SomethingAsync() { return Task.Factory.FromAsync<T>( _apm.BeginSomething, _apm.EndSomething, null); } } https://gist.github.com/alextercete/f34691cb9e4df4d2e78b
23. .NET 4.0+ TPL public interface IDependency<T> { Task<object> BeforeAsync(); Task<T> AfterAsync(object result); } https://gist.github.com/alextercete/a011bafde7187104303b
24. .NET 4.0+ TPL public interface IDependency<T> { Task<object> BeforeAsync(); Task<T> AfterAsync(object result); } https://gist.github.com/alextercete/a011bafde7187104303b
25. .NET 4.0+ TPL public class TaskParallelLibrary<T> { private readonly IDependency<T> _dependency; // Constructor public Task<T> SomethingAsync() { return _dependency.BeforeAsync().ContinueWith( previous => _dependency.AfterAsync(previous.Result) ).Unwrap(); } } https://gist.github.com/alextercete/a011bafde7187104303b
26. .NET 4.0+ TPL public class TaskParallelLibrary<T> { private readonly IDependency<T> _dependency; // Constructor public Task<T> SomethingAsync() { return _dependency.BeforeAsync().ContinueWith( previous => _dependency.AfterAsync(previous.Result) ).Unwrap(); } } https://gist.github.com/alextercete/a011bafde7187104303b
27. .NET 4.5+ async/await public class TaskParallelLibrary<T> { private readonly IDependency<T> _dependency; // Constructor public async Task<T> SomethingAsync() { var result = await _dependency.BeforeAsync(); return await _dependency.AfterAsync(result); } } https://gist.github.com/alextercete/a011bafde7187104303b
28. .NET 4.5+ async/await public class TaskParallelLibrary<T> { private readonly IDependency<T> _dependency; // Constructor public async Task<T> SomethingAsync() { var result = await _dependency.BeforeAsync(); return await _dependency.AfterAsync(result); } } https://gist.github.com/alextercete/a011bafde7187104303b
29. Use async/await
30. Os 8 erros mais comuns O #5 vai fazer você se emocionar
31. public interface IDependency<T> { Task<object> BeforeAsync(); Task<T> AfterAsync(object result); Task<T> SomethingAsync(); Task<T> SomethingAsync(CancellationToken token); Task<T> SomethingAsync( Func<object, Task<T>> callback); } https://gist.github.com/alextercete/1acbaf93605383fcea51
32. #1 O código quase assíncrono
33. public class TheAlmostAsync<T> { // Private fields and constructor public T Something() { return SomethingAsync().Result; } public async Task<T> SomethingAsync() { var result = await _dependency.BeforeAsync(); return await _dependency.AfterAsync(result); } } https://gist.github.com/alextercete/1acbaf93605383fcea51
34. public class TheAlmostAsync<T> { // Private fields and constructor public T Something() { return SomethingAsync().Result; } public async Task<T> SomethingAsync() { var result = await _dependency.BeforeAsync(); return await _dependency.AfterAsync(result); } } https://gist.github.com/alextercete/1acbaf93605383fcea51
35. public class TheAlmostAsync<T> { // Private fields and constructor public T Something() { return SomethingAsync().Result; } public async Task<T> SomethingAsync() { var result = await _dependency.BeforeAsync(); return await _dependency.AfterAsync(result); } } https://gist.github.com/alextercete/1acbaf93605383fcea51
36. https://www.flickr.com/photos/justinjensen/4710621230
37. return SomethingAsync().Result; Something Thread x
38. return SomethingAsync().Result; Something Contexto Thread x
39. return SomethingAsync().Result; Something SomethingAsync var result = await _dependency.BeforeAsync(); return await _dependency.AfterAsync(result); Contexto Thread y Thread x
40. return SomethingAsync().Result; Something SomethingAsync var result = await _dependency.BeforeAsync(); return await _dependency.AfterAsync(result); Contexto Thread y Thread x
41. public class TheAlmostAsyncFixed<T> { // Private fields and constructor public T Something() { return SomethingAsync().Result; } public async Task<T> SomethingAsync() { var result = await _dependency.BeforeAsync().ConfigureAwait(false); return await _dependency.AfterAsync(result).ConfigureAwait(false); } } https://gist.github.com/alextercete/1acbaf93605383fcea51
42. Use .ConfigureAwait(false) em código de bibliotecas
43. #2 O código pseudo-assíncrono
44. public class ThePseudoAsync<T> { public async Task<T> SomethingAsync() { return default(T); } } https://gist.github.com/alextercete/1acbaf93605383fcea51
45. public class ThePseudoAsync<T> { public async Task<T> SomethingAsync() { return default(T); } } https://gist.github.com/alextercete/1acbaf93605383fcea51
46. Síncrono até encontrar o primeiro ponto de assincronia
47. #3 O código super-assíncrono
48. public class TheSuperAsync<T> { // Private fields and constructor public async Task<T> SomethingAsync() { return await _dependency.SomethingAsync( async result => await _dependency.AfterAsync(result)); } } https://gist.github.com/alextercete/1acbaf93605383fcea51
49. public class TheSuperAsync<T> { // Private fields and constructor public async Task<T> SomethingAsync() { return await _dependency.SomethingAsync( async result => await _dependency.AfterAsync(result)); } } https://gist.github.com/alextercete/1acbaf93605383fcea51
50. public class TheSuperAsync<T> { // Private fields and constructor public async Task<T> SomethingAsync() { return await _dependency.SomethingAsync( async result => await _dependency.AfterAsync(result)); } } https://gist.github.com/alextercete/1acbaf93605383fcea51
51. public class TheSuperAsyncFixed<T> { // Private fields and constructor public Task<T> SomethingAsync() { return _dependency.SomethingAsync( result => _dependency.AfterAsync(result)); } } https://gist.github.com/alextercete/1acbaf93605383fcea51
52. Evite async/await quando não for necessário
53. #4 O retorno nulo
54. public class TheNullReturn<T> { // Private fields and constructor public Task<T> AfterAsync(object result) { if (result == null) return null; return _dependency.AfterAsync(result); } } https://gist.github.com/alextercete/1acbaf93605383fcea51
55. public class TheNullReturn<T> { // Private fields and constructor public Task<T> AfterAsync(object result) { if (result == null) return null; return _dependency.AfterAsync(result); } } https://gist.github.com/alextercete/1acbaf93605383fcea51
56. public class TheNullReturnFixed<T> where T : class { // Private fields and constructor public Task<T> AfterAsync(object result) { if (result == null) return Task.FromResult<T>(null); return _dependency.AfterAsync(result); } } https://gist.github.com/alextercete/1acbaf93605383fcea51
57. #5 O contexto perdido
58. Verifique se isso está em seu Web.config
59. <httpRuntime targetFramework="4.5" /> <appSettings> <add key="aspnet:UseTaskFriendlySynchronizationContext" value="true" /> </appSettings> OU
60. public class TheMissingContext<T> { // Private fields and constructor public async Task<T> SomethingAsync() { var result = await _dependency.BeforeAsync() .ConfigureAwait(false); // HttpContext.Current == null return await _dependency.AfterAsync(result) .ConfigureAwait(false); } } https://gist.github.com/alextercete/1acbaf93605383fcea51
61. public class TheMissingContextFixed<T> { // Private fields and constructor public async Task<T> 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
62. #6 A chamada esquecida
63. public class TheForgottenCall<T> { // Private fields and constructor public Task SomethingAsync() { SomethingNotAsync(); return CompletedTask; } private async void SomethingNotAsync() { await _dependency.BeforeAsync(); } } https://gist.github.com/alextercete/1acbaf93605383fcea51
64. https://gist.github.com/alextercete/1acbaf93605383fcea51 public class TheForgottenCall<T> { // 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); } }
65. public class TheForgottenCall<T> { // Private fields and constructor public Task SomethingAsync() { SomethingNotAsync(); return CompletedTask; } private async void SomethingNotAsync() { await _dependency.BeforeAsync(); } } https://gist.github.com/alextercete/1acbaf93605383fcea51
66. public class TheForgottenCallFixed<T> { // Private fields and constructor public async Task SomethingAsync() { await SomethingNowAsync(); } private async Task SomethingNowAsync() { await _dependency.BeforeAsync(); } } https://gist.github.com/alextercete/1acbaf93605383fcea51
67. Nunca use async void
68. public class TheForgottenCall<T> { // Private fields and constructor public Task AfterAsync(object result) { _dependency.AfterAsync(result); return CompletedTask; } } https://gist.github.com/alextercete/1acbaf93605383fcea51
69. public class TheForgottenCall<T> { // Private fields and constructor public Task AfterAsync(object result) { _dependency.AfterAsync(result); return CompletedTask; } } https://gist.github.com/alextercete/1acbaf93605383fcea51
70. public class TheForgottenCallFixed<T> { // Private fields and constructor public async Task AfterAsync(object result) { await _dependency.AfterAsync(result); } } https://gist.github.com/alextercete/1acbaf93605383fcea51
71. public class TheForgottenCallReallyFixed<T> { // Private fields and constructor public Task AfterAsync(object result) { return _dependency.AfterAsync(result); } } https://gist.github.com/alextercete/1acbaf93605383fcea51
72. #7 O cancelamento ignorado
73. public class TheIgnoredCancellation<T> { // Private fields and constructor public Task<T> SomethingAsync(CancellationToken token) { return _dependency.SomethingAsync(); } } https://gist.github.com/alextercete/1acbaf93605383fcea51
74. public class TheIgnoredCancellation<T> { // Private fields and constructor public Task<T> SomethingAsync(CancellationToken token) { return _dependency.SomethingAsync(); } } https://gist.github.com/alextercete/1acbaf93605383fcea51
75. public class TheIgnoredCancellationFixed<T> { // Private fields and constructor public Task<T> SomethingAsync(CancellationToken token) { return _dependency.SomethingAsync(token); } } https://gist.github.com/alextercete/1acbaf93605383fcea51
76. O cancelamento depende de quem observa o token
77. #8 A disputa pelas threads
78. public class TheThreadsDispute<T> { // Private fields and constructor public T Something() { return Task.Run(() => _dependency.SomethingAsync()).Result; } public IList<T> Somethings(int count) { var results = new List<T>(count); Parallel.For(0, count, i => results[i] = _dependency.SomethingAsync().Result); return results; } } https://gist.github.com/alextercete/1acbaf93605383fcea51
79. public class TheThreadsDispute<T> { // Private fields and constructor public T Something() { return Task.Run(() => _dependency.SomethingAsync()).Result; } public IList<T> Somethings(int count) { var results = new List<T>(count); Parallel.For(0, count, i => results[i] = _dependency.SomethingAsync().Result); return results; } } https://gist.github.com/alextercete/1acbaf93605383fcea51
80. public class TheThreadsDispute<T> { // Private fields and constructor public T Something() { return Task.Run(() => _dependency.SomethingAsync()).Result; } public IList<T> Somethings(int count) { var results = new List<T>(count); Parallel.For(0, count, i => results[i] = _dependency.SomethingAsync().Result); return results; } } https://gist.github.com/alextercete/1acbaf93605383fcea51
81. https://www.flickr.com/photos/eustaquio/10556254584
82. Thread Pool Requests Queue
83. Thread Pool Requests Queue
84. Thread Pool Requests Queue
85. Thread Pool Requests Queue
86. Thread Pool Requests Queue
87. Thread Pool Requests Queue
88. Thread Pool Requests Queue
89. Thread Pool Requests Queue
90. Thread Pool Requests Queue
91. Thread Pool Requests Queue
92. Thread Pool Requests Queue
93. Thread Pool Requests Queue
94. Thread Pool Requests Queue
95. Em cenários de alta concorrência, economize threads
96. public class TheThreadsDisputeFixed<T> { // Private fields and constructor public T Something() { return _dependency.SomethingAsync().Result; } public IList<T> Somethings(int count) { var results = new List<T>(count); Parallel.For(0, count, i => results[i] = _dependency.SomethingAsync().Result); return results; } } https://gist.github.com/alextercete/1acbaf93605383fcea51
97. public class TheThreadsDisputeFixed<T> { // Private fields and constructor public T Something() { return _dependency.SomethingAsync().Result; } public IList<T> Somethings(int count) { var tasks = Enumerable.Range(0, count).Select( i => _dependency.SomethingAsync()); return Task.WhenAll(tasks).Result; } } https://gist.github.com/alextercete/1acbaf93605383fcea51
98. public class TheThreadsDisputeReallyFixed<T> { // Private fields and constructor public Task<T> SomethingAsync() { return _dependency.SomethingAsync(); } public async Task<IList<T>> SomethingsAsync(int count) { var tasks = Enumerable.Range(0, count).Select( i => _dependency.SomethingAsync()); return await Task.WhenAll(tasks); } } https://gist.github.com/alextercete/1acbaf93605383fcea51
99. https://www.flickr.com/photos/eschipul/4160817135
100. https://www.flickr.com/photos/22897666@N00/6883636817
101. 3 minutos 15 segundos
102. Se a espera for pequena, a troca de contexto não compensa
103. 1 minuto 10 minutos
104. 21 0 t
105. 21 0 t
106. Sempre haverá um gargalo
107. 5 minutos 3 minutos
108. 21 0 t
109. 21 0 t
110. http://commons.wikimedia.org/wiki/File:Israel_Austerity.jpg
111. Se a fila estiver grande, os clientes irão embora
112. Dúvidas?
113. Obrigado! Alex Tercete tercete@vtex.com.br
114. 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
115. 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/