COMIC BOOK GRAPHIC NOVEL APPROACH TO ASYNC

Transcription

1 KATHLEEN DOLLARD - KATHLEENDOLLARD KATHLEEN@MVPS.ORG BLOG: HT TP:// - DOLLARD Puzzles Workshop

2 Puzzles

3 EXPLORING THE SURPRISES IN.NET

4 COMIC BOOK GRAPHIC NOVEL APPROACH TO ASYNC

5

6 Async and Multi-threading are different Async Multi-thread

7 Async and Multi-threading are different Async Multi-thread

8 Async and Multi-threading are different Async Operations overlap with other operations Long file operations, database calls or network requests Asynchronous operations may not be multi-threaded Mads Torgersen: discontinuous sequential operations Multi-thread Multiple operations sharing CPU Multi-threaded operations are asynchronous Get Async right, then do multi-threading

9 Job Today Believe that async doesn t require threads Understand how your code is split up on compile Catch how exceptions pass through async code Learn about WhenAny and WhenAll combinators See how threads start with Run Comprehend cancellation and timeout Know how to report progress Look at concurrency issues Demo debugging

10 Message pump Click Sub Button1_Click(...) LoadSettings() UpdateView() End Sub Sub LoadSettings() IO.File.ReadAllText(path) End Sub Click Thanks Greg Paparin!

11 Message pump Click Sub Button1_Click(...) LoadSettings() UpdateView() End Sub Sub LoadSettings() IO.Network.Download(path) End Sub Click Thanks Greg Paparin!

12 Click Message pump Async Sub Button1_Click(...) Await LoadSettingsAsync() UpdateView() Task... LoadSettings End Sub Async Function LoadSettingsAsync() As Task LoadSettingsAsync Await IO.Network.DownloadAsync(path) End Sub Task... Download DownloadAsync Click Thanks Greg Paparin!

13 Start End Kathleen Dollard. All rights reserved.

14 Start End Kathleen Dollard. All rights reserved.

15 Start End Kathleen Dollard. All rights reserved.

16 Start End Kathleen Dollard. All rights reserved.

17 Start End Task 1 Object Kathleen Dollard. All rights reserved.

18 Start End Task 1 Object 2012 Kathleen Dollard. All rights reserved.

19 Your code Your continuation Task Object Main Thread Event NOMT Not on main thread private async Task<int> LongOp() { Console.WriteLine("1.In LongOp"); await Task.Delay(3000)); Console.WriteLine("3.Done!"); return 42; } 19

20 Your code Your continuation Task Object Main Thread Event NOMT Not on main thread private async Task<int> LongOp() { Console.WriteLine("1.In LongOp"); await Task.Delay(3000)); Console.WriteLine("3.Done!"); Console.WriteLine("3.Done!"); return 42; return 42; } 20

21 Logical Code Rewriting Task Object () => { private async Task<int> LongOp() { Console.WriteLine("1.In LongOp"); await Task.Delay(3000)); Console.WriteLine("3.Done!"); Console.WriteLine("3.Done!"); return 42; return 42; } }

22 Code Rewriting with Variable Task Object private async Task<int> LongOp() { Console.WriteLine("1.In LongOp"); int val = 3; await Task.Delay(3000)); Console.WriteLine(val +" Done!"); Console.WriteLine(val + "Done!"); return 42; return 42; } () => { }

23 Your code Your continuation Main Thread Task Object System.IO wrapper Event NOMT Not on main thread 23

24 Code Continuation Code Continuation Task Object Main Thread System.IO wrapper NOMT Not on main thread 24

25 Your code Your continuation Main Thread Task Object System.IO wrapper Event NOMT Not on main thread 25

26 Your code Your continuation Task Object Main Thread System.IO Task.Run() wrapper NOMT Not on main thread 26

27 Async Exceptions

28 Your code Your continuation Main Thread Task Object System.IO wrapper catch { // handle and/or // rethrow NOMT Not on main thread Catch can appear anywhere in continuation stack 30

29 Combinators WHENALL, WHENANY, RUN, FROMRESULT, DELAY

30 Task.WhenAll Asynchronously await completion of all tasks Task.WhenAny Asynchronously await one of multiple tasks Task.Run Run a task using the thread pool Task.FromResult Immediately return result lifted into a task for task returning method Task.Delay Non-blocking timer for delays (use instead of Thread.Sleep) Create your own combinators Which really just means create appropriate helper classes Examples include RetryOnFault and WhenAllOrFirstException

31 Your code Continuation WhenAll task Task Object Task Object Task Object Main Thread wrapper wrapper wrapper NOMT Not on main thread 33

32 Your code Continuation Task WhenAll Object task Task Object Task Object Task Object Main Thread wrapper wrapper wrapper NOMT Not on main thread 34

33 Your code Continuation WhenAll task Task Object Task Object Task Object Main Thread wrapper wrapper wrapper NOMT Not on main thread 35

34 Your code Continuation WhenAll task Task Object TaskObject Task Object Main Thread wrapper wrapper wrapper NOMT Not on main thread 36

35 When to Use WhenAll Tasks to run at the same time Example: multiple web requests There is no dependency between tasks One task doesn t depend on the result of a previous task If dependencies exist, use sequential async processing All tasks need to complete, or all results are required, before the continuation occurs The same exception handling (catch) is needed for all tasks Exceptions appear in the tasks aggregate exception First exception is also thrown All of the results are supplied in the resulting array

36 WhenAll vs. Sequential Async Operations

37 Your code Continuation Task Object Task Object wrapper Main Thread NOMT Not on main thread 39

38 Your code Continuation Task Object Task Object wrapper Main Thread NOMT Not on main thread 40

39 Your code Continuation Task Object Task Object wrapper Main Thread NOMT Not on main thread 41

40 ur code Task Object Task Object Continuation Task Object Task Object Continuation wrapper wrapper 42

41 You only care about one result Redundant operations of which you only need one result Possibly interleaving (examples on Internet and in my video) You want to work with each result as soon as it is available Consider using TPL for this Possibly throttling (examples on Internet and in my video) You are using multiple threads and wish to control number used although this is very rarely needed: Stephen Toub says really, really, really rare If you do need to throttle probably use an alternate task scheduler, SemaphoreSlim.WaitAsync, or Dataflow and need to read Stephen Toub s blog Cancellation Timeout without cancellation token source Early bail with operations that don t support cancellation Part of complex scenarios

42 WhenAny

43 Your code Continuation Task Object Task Object Task Object Task Object Main Thread wrapper wrapper wrapper NOMT Not on main thread 45

44 Your code Continuation Task Object Task Object Task Object Task Object Main Thread wrapper wrapper wrapper NOMT Not on main thread 46

45 Your code Continuation Task Object Task Object Task Object Task Object Main Thread wrapper wrapper wrapper NOMT Not on main thread 47

46 Your code Continuation Task Object Task Object TaskObject Task Object Main Thread wrapper wrapper wrapper NOMT Not on main thread 48

47 Consuming the Task-based Asynchronous Pattern Note: There is a second more efficient interleaving pattern far down on that page 49

48 Starts a new thread Task.Run(action) Static method which returns a Task object Action can be a lambda expression or a delegate C# will wrap the delegate to a lambda for you It can also be a Task, allowing async/await within the action Allows you to explicitly start a task on another thread from the pool Overloads include parameters that supporting cancellation If you previously used TPL, this replaces Task.Factory.StartNew()

49 Your code Your continuation Task.Run Object Main Thread Thread from thread pool 51

50 Sometimes, data is available & can just be returned Since the method returns a task, we still need one public Task<int> GetValueAsync(string key) { int cachedvalue; return TryGetCachedValue(out cachedvalue)? Task.FromResult(cachedValue) : GetValueAsyncInternal(); } private async Task<int> GetValueAsyncInternal(string key) { }

51 Your code Your continuation Main Thread NOMT Not on main thread 54

52 Task.Delay Allows non-blocking wait Thread doesn t sleep Calling thread is not blocked

53 Your code Your continuation Main Thread Task Object NOMT Doesn t block main thread 56

54 Cancellation

55 Other code, like button click Your code Main Thread NOMT Not on main thread 62

56 Cancellation

57 Cancellation CancellationTokenSource Contains CancellationToken Can initiate cancel Can link CancellationTokens (logically nesting) CancellationToken Can be marked canceled by TokenSource Operations can watch and prematurely end Cannot initiate cancellation Do not accept cancellation tokens in methods that cannot logically cancel

58 Other code, like button click Your code Your continuation Task Object Main Thread NOMT Not on main thread 65

59 Other code, like button click Your code Your continuation Task Object Main Thread Operation wrapper NOMT Not on main thread 66

60 Other code, like button click Your code Your continuation Exception Catch Task Object Main Thread Operation wrapper NOMT Not on main thread 67

61 WhenAny with Task.Delay representing the timeout Requires special code You raise timeout exception Different times, options Does not affect other tasks Does not share token source Logically differentiated code Timeout property on the CancellationTokenSource Very, very simple Automatically ends subtasks If they take CTS Raises timeout exception Task is canceled, not faulted Single timeout for source Can t get partial results Linked sources share CTS Can register special behavior

62 Your code Continuation Task Object Task Object Task.Delay wrapper Main Thread NOMT Not on main thread 69

63 Your code Continuation Task Object Task Object Task.Delay wrapper Main Thread NOMT Not on main thread 70

64 Your code Continuation Task Object Task Object Task Task.Delay wrapper Main Thread NOMT Not on main thread 71

65 Your code Your continuation Task Object Main Thread NOMT Not on main thread 72

66 Your code Your continuation Task Object Main Thread Operation wrapper NOMT Not on main thread 73

67 Your code Your continuation Exception Catch Task Object Main Thread Operation wrapper NOMT Not on main thread 74

68 Progress

69 Progress Type System.IProgress interface void Report(T value) System.Progress<T> class public Progress() public Progress(Action<T> callback) public event EventHandler<T> ProgressChanged protected virtual OnReport method void IProgress<T>.Report( T value)

70 Your code Your continuation Task Object IProgress Main Thread Task.Run Thread from the thread pool IProgress.Report 77

71 Progress Types System.IProgress interface void Report(T value) System.Progress<T> class public Progress() public Progress(Action<T> callback) public event EventHandler<T> ProgressChanged protected virtual OnReport method void IProgress<T>.Report( T value)

72 ProgressChanged event or callback Your code Your continuation Task Object Progress Main Thread System.IO Task.Run wrapper Thread from the thread pool IProgress.Report 79

73 Logical Context for Async and Multi-threading Client applications maintain a single UI thread Important to move blocking tasks like network calls off of this thread Web servers fill requests with a new thread from the thread pool Creating new threads implicitly or explicitly can lower throughput Short blocks on the main request thread is sometimes better Except simple scenarios, plan performance profiling if important Special considerations for unit testing Kathleen Dollard. All rights reserved.

74 Debugging Features Async debugging It just works Parallel debugging improvements Parallel Watch Concurrency Visualizer Flagging threads Debug Location toolbar Breakpoint filters Demo cool features in a wacky app Not covering GPU Threads window

75 Wacky Application to Practice Debugging There is a Clip in Module 4 (11C) of my Pluralsight course on multi-threaded debugging. What s New in.net 4.5, Pluralsight, To access a similar app and practice debugging, use this help link Topic: Walkthrough: Debugging a Parallel Application Currently at Will be most useful if you actually do the walk-through

76 Next Steps Watch my video If you don t have a Pluralsight subscription one month trial, WHAT!? Use async/await in a test application without multi-threading Probably a UI application Do NOT do CPU intensive stuff or Thread.Sleep Create a multi-threaded application for the desktop Get off the main UI thread as much as possible Play with features like Progress Create an async application for a server Preserve threads Consider a web call Use caution considering multi-threading on server

77 LINQ

78 LINQ Demos Lambdas and Functional Programming LINQ Queries Performance Operators/Methods Complex Queries Expressions and Providers

79 Tracing SOUNDS BORING?

80 Understanding Production Applications NOT SO BORING?

81 Things that make debugging hard Desktop Rare Distance (can t sit down and watch) Watching doesn t help Registry corruption/error Machine dependent issues o Hookup Visual Studio remote debugging? o Run Visual Studio on your server? o Buy Ultimate for IntelliTrace? Server Same issues as desktop plus Inter-process issues Higher pressure on threads and memory Authorization issues Not being an admin

82 Two Independent Themes Abstract your tracing Appropriate server tracing Out-of-proc EventSource and ETW, possibly through SLAB Holistic

83 Tracing A mechanism for recording the path currently being taken through your application

84 Your life without tracing Your life with abstracted, semantic, out-of-proc tracing

85 Abstract!

86 Production Code Semantic Log Abstraction Your Logging Framework Production Code Your Logging Framework Abstraction Over Your Logging Framework System Trace.Write(...) Logger.Log.OpenFile(...) Specific Task

87 Semantic or Abstract Logging private void FireEvent2_Click(object sender, RoutedEventArgs e) { Logger.Log.Message("Test message"); } private void KeyEvent2_Click(object sender, RoutedEventArgs e) { Logger.Log.AccessByPrimaryKey(GetPrimaryKey(), "Customer"); } Strongly typed, IntelliSense driven Details like keywords and level defined/changed at central point Aids code readability Logging framework/tool agnostic

88 Semantic or Abstract Logging Trace.WriteLine(string.Format( Access {0} Primary Key {1}, Customer,42); Resulting string is not strongly typed Must be read by a human Or parsed in a fragile manner Ties logging to technology Log.AccessByPrimaryKey( Customer, 42); Easier to read intent Resulting log is strongly typed Can be used with any logging technology and can shift during project

89 Tracing records the path through your app Outside forces affect your app.net Operating system Service/web calls Many others o ETW integrates view of your application with outside factors - holistic

90 Old-Style Tracing You create the entire picture Tools roughly give you a crayon to draw with Technique Trace.WriteXxxx TraceSource Third-party such as Log4Net In-process recording devastates scalability

91 New-Style Tracing with EventSource or SLAB Out-of-proc: Very, very fast because off-thread immediately Holistic: Vast amount of data already available Orienteering: Your app drops locations like GPS points

92 On and off, filtering ETW Design Create trace entry ETW Session ETW Session ETW Controller ETW Session ETW Session ETW Provider ETW Sessions managed by the operating system ETW Session ETW Session ETW Session Observe, access trace info ETW Session ETW Session ETW Consumer

93 What happens Controller Consumer

94 Asd fdaf fdjkdhf Sadf Fkjkdslak Fdd Black Box Tracing

95 Black Box Tracing

96 Black Box Tracing

97 Black Box Tracing

98 Demo PERFVIEW

99 Naming is Very Confusing System.Diagnostics Old stuff System.Diagnostics.Tracing New stuff (.NET 4.5) EventSource EventListener Microsoft.Diagnostics.Tracing TraceSource TraceEvent Method EventSource TraceEvent Class TraceListener EventListener

100 ETW Design - Processes ETW Session ETW Session ETW Controller ETW Session ETW Session ETW Provider Your App ETW Sessions managed by the operating ETW system ETW ETW Session Session Session ETW ETW Session Session ETW Consumer

101 ETW Design - Manifests ETW Session ETW Session ETW Controller ETW Session ETW Session ETW Provider ETW Sessions managed by the operating ETW system ETW ETW Session Session Session ETW ETW Session Session ETW Consumer

102 ETW Design - Manifests ETW Session ETW Session ETW Controller ETW Session ETW Session ETW Provider ETW Sessions managed by the operating ETW system ETW ETW Session Session Session Binary File Manifest ETW ETW Session Session ETW Consumer

103

104 ETW Design - Manifests ETW Session ETW Session ETW Controller ETW Session ETW Session ETW Provider ETW Sessions managed by the operating ETW system ETW ETW Session Session Session Binary File Manifest ProviderId EventId, Version Manifest ETW ETW Session Session ETW Consumer

105 ETW Design - Manifests ETW Session ETW Session ETW Controller ETW Session ETW Session ETW Provider ETW Sessions managed by the operating ETW system ETW ETW Session Session Session Binary File Manifest ProviderId EventId, Version Guid ETW ETW Session Session ETW Consumer Integer, small, non-zero optional Created from string via standard algorithm

106 ETW Design - Manifests ETW Session ETW Session ETW Controller ETW Session ETW Session ETW Provider ETW Sessions managed by the operating ETW system ETW ETW Session Session Session Binary File Manifest ETW ETW Session Session ETW Consumer

107 ETW Design - Manifests ETW Session ETW Session ETW Controller ETW Session ETW Session ETW Provider ETW Sessions managed by the operating ETW system ETW ETW Session Session Session Binary File Manifest ETW ETW Session Session ETW Consumer

108 ETW Design - Manifests ETW Session ETW Session ETW Controller ETW Session ETW Session ETW Provider ETW Sessions managed by the operating ETW system ETW ETW Session Session Session Binary File Manifest Manifest ETW ETW Session Session ETW Consumer

109 ETW Design - Manifests ETW Session ETW Session ETW Controller ETW Session ETW Session ETW Provider ETW Sessions managed by the operating ETW system ETW ETW Session Session Session Binary File Manifest ETW ETW Session Session ETW Consumer

110 ETW Design Summary ETW is composed of Core (sessions) Controllers Providers Consumers ETW does most of the work outside your process Particularly important for resources like writing files ETW is blazingly fast It s in the operating system It creates binary files or streams Manifests explain how to interpret binary files Contain provider IDs (use strings), event IDs (integers 0, 1 ), and payload def Can be registered on the machine Can be in-line in a message

111 Audiences ETW Session ETW Session ETW Controller ETW Session ETW Session ETW Provider ETW Sessions managed by the operating ETW system ETW ETW Session Session Session ETW ETW Session Session ETW Consumer

112 Writing to Channels Debug.NET 4.5 System.Diagnostics.Tracing. EventSource class Analytic.NET 4.6 or NuGet Microsoft.Diagnostics.Tracing. EventSource class Supports in-line and installed manifests Admin Operational Installed Manifest

113 Demo CREATE SEMANTIC LOGGING

114 EventSource Structure System.Diagnostics.Tracing.EventSource Your custom event source class Static Log property Method for each event type Parameter for interesting data Call to WriteEvent

115 EventSource Structure System.Diagnostics.Tracing.EventSource Your custom event source class Static Log property Method for each event type Parameter for interesting data Call to WriteEvent

116 Event EventSource Important Attribute Parameters Property Default Recommended Name Non-namespace qualified class name Use a hierarchical name meaningful to the consumer does not need to contain the class name DO NOT use the default value Guid Derived from name and also called the ProviderId Do not specify but allow to be derived from the name Property Default EventId Ordinal from top of class Must match value passed to WriteEvent Unique identifier for the event

117 Performance Summary Cached Logger int/string Object Overload Event Off Yes 9ns 100M 20ns 50M Event Watched Yes 410ns 2M 720ns 1M Event Off No 9ns 100M 19ns 50M Event Watched No 410ns 2M 730ns 50M Integer and string constants same speed Caching the logger does not alter performance Object overload is approximately twice as slow Non-watched events are nearly free See guidelines in my course (What s New & ETW) or blog!

118 Demo EXPLORE CODE PERFVIEW AGAINST RUNNING APP

119 SLAB Benefits over direct use Familiar development experience/familiar listeners (ETW not required) Really nice documentation Builds on EventSource, so you get those benefits for free Not even an intervening class Build/test time tools to validate providers In process as well of as out of process logging But use out-of-proc Alternate and multiple listeners IObservable support

120 Summary ETW Architecture Controllers, consumers, providers Manifests installed (NuGet) or in-line Channels supported in NuGet version A few tools WPA in Win 8.1 SDK and PerfView EventSource.NET 4.5 (also has EventListener which you don t care much about use SLAB).NET (validation at build, trace diagnostics-event Zero/constructor) NuGet (4.0 support, channels, validation at build, trace diagnostics-event Zero/constructor, correlation) Patterns and Practices Semantic Logging Application Block for simple development time listeners Use only ETW as production listener and controller

121 ETW Design Summary ETW is composed of Core (sessions) Controllers Providers Consumers ETW does most of the work outside your process Particularly important for resources like writing files ETW is blazingly fast It s in the operating system It creates binary files or streams Manifests explain how to interpret binary files Contain provider IDs (use strings), event IDs (integers 0, 1 ), and payload def Can be registered on the machine Can be in-line in a message

122 Overly Simple (bad) EventSource namespace EventDefinitions { public class SimpleEventSource : EventSource } {static public SimpleEventSource Log } = new SimpleEventSource(); public void Message(string Message) { WriteEvent(1, Message); } public void AccessByPrimaryKey( int PrimaryKey, string TableName) { WriteEvent(2, PrimaryKey, TableName); } Please define a few things Default Id is SimpleEventSource These must match the order of logging methods in the file Parameters/args must match

123 Normal (good) EventSource [EventSource(Name = "KadGen-EtwSamples-Normal")] public class NormalEventSource : EventSource { static public NormalEventSource Log = new NormalEventSource(); [Event(1)] public void Message(string Message) { WriteEvent(1, Message); } [Event(2)] public void AccessByPrimaryKey( int PrimaryKey, string TableName) Please define a few things } { WriteEvent(2, PrimaryKey, TableName); }

124 Semantic Logging Application Block SLAB Uses EventSource (.NET 4.5+) No other dependencies Fantastic documentation, including semantic logging concepts Out-of-proc provides consumers you re familiar with Use in-proc if it s the best your team can do now Sadly, lag behind EventSource version

125 My blog: on Twitter Free Series Pluralsight, Kathleen Dollard Event Tracing for Windows (ETW) in.net, Puzzles, What s New in.net 4.5, Module 3 is ETW Visual Studio 2015 Analyzers, upcoming Vance Morrison s blog: SLAB