Akka.NET流处理：模块化、组合与层次结构设计指南-优快云博客

Akka.NET流处理：模块化、组合与层次结构设计指南

akka.net Canonical actor model implementation for .NET with local + distributed actors in C# and F#. 项目地址: https://gitcode.com/gh_mirrors/ak/akka.net

概述

Akka.NET Streams提供了一套统一的流处理图模型，允许开发者通过可重用组件的灵活组合来构建复杂的流处理系统。本文将深入探讨Akka.NET Streams中的模块化设计理念、组件组合方式以及层次结构构建方法。

基础概念：组件即"盒子"

在Akka.NET Streams中，每个处理阶段都可以视为具有输入和输出端口的"盒子"：

Source：单输出端口盒子
Sink：单输入端口盒子
Flow：单输入单输出端口盒子
BidiFlow：双输入双输出端口盒子（常用于双向通信场景）

基础组件形状

这种抽象模型使得各种处理阶段能够以统一的方式进行组合和嵌套。

模块化设计实践

基础组合

最简单的组合方式是线性连接各个组件：

Source.Single(0)
    .Select(x => x + 1)
    .Where(x => x != 0)
    .Select(x => x - 2)
    .To(Sink.Aggregate<int, int>(0, (sum, x) => sum + x));

命名与封装

通过Named()方法可以为组件创建逻辑边界，实现模块化：

var nestedSource = Source.Single(0)
    .Select(x => x + 1)
    .Named("nestedSource");

var nestedFlow = Flow.Create<int>()
    .Where(x => x != 0)
    .Select(x => x - 2)
    .Named("nestedFlow");

var nestedSink = nestedFlow
    .To(Sink.Aggregate<int, int>(0, (sum, x) => sum + x))
    .Named("nestedSink");

var runnableGraph = nestedSource.To(nestedSink);

复杂图结构构建

对于非线性图结构，可以使用GraphDSL：

RunnableGraph.FromGraph(GraphDsl.Create(builder =>
{
    var broadcast = builder.Add(new Broadcast<int>(2));
    var merge = builder.Add(new Merge<int>(2));
    
    builder.From(Source.Single(0)).To(broadcast);
    builder.From(broadcast.Out(0)).To(merge.In(0));
    builder.From(broadcast.Out(1))
        .Via(Flow.Create<int>().Select(x => x + 1))
        .To(merge.In(1));
    
    builder.From(merge).To(Sink.ForEach<int>(Console.WriteLine));
    
    return ClosedShape.Instance;
}));

高级模块化技巧

部分图创建

可以创建可重用的部分图：

var partialGraph = GraphDsl.Create(builder =>
{
    var broadcast = builder.Add(new Broadcast<int>(2));
    var merge = builder.Add(new Merge<int>(2));
    
    builder.From(broadcast.Out(0)).To(merge.In(0));
    builder.From(broadcast.Out(1))
        .Via(Flow.Create<int>().Select(x => x + 1))
        .To(merge.In(1));
    
    return new FlowShape<int, int>(broadcast.In, merge.Out);
}).Named("partialGraph");

形状转换

将部分图转换为特定形状的组件：

var flowFromPartial = Flow.FromGraph(partialGraph);
var sourceFromPartial = Source.FromGraph(partialGraph);

物化值处理

每个组件在物化时都可能产生物化值，组合时需要特别注意：

// 保留左侧物化值
var source = Source.Maybe<int>();
var flow = Flow.Create<int>().Take(100);
var nestedSource = source.ViaMaterialized(flow, Keep.Left);

// 保留右侧物化值
var flow1 = Flow.Create<int>().Select(x => x.ToString());
var flow2 = Sys.TcpStream().OutgoingConnection("localhost", 8080);
var nestedFlow = flow1.ViaMaterialized(flow2, Keep.Right);

// 保留两侧物化值
var sink = Sink.Aggregate<string, string>("", (agg, s) => agg + s);
var nestedSink = nestedFlow.ToMaterialized(sink, Keep.Both);