我正在尝试使用 Automatonymous 和 RabbitMQ 为状态机实现一个简单的示例/演示。不幸的是,我找不到一个可以重建/学习的(我找到了 ShoppingWeb ,但在我看来它一点也不简单)。在我看来,文档也缺少信息。
这是我想到的状态机示例(抱歉,它很丑): 请注意,这个例子完全是虚构的,它是否有意义并不重要。该项目的目的是让 Automatonymous 变得“温暖”。
我想做/想拥有的是:
- 正在运行的四个应用程序:
- 状态机本身
- “请求者”发送请求进行解释
- “验证器”或“解析器”检查提供的请求是否有效
- 解释给定请求的“解释器”
- 例如:
- 请求者发送“x=5”
- 验证器检查是否包含“=”
- 口译员说“5”
我的状态机实现如下所示:
public class InterpreterStateMachine : MassTransitStateMachine<InterpreterInstance>
{
public InterpreterStateMachine()
{
InstanceState(x => x.CurrentState);
Event(() => Requesting, x => x.CorrelateBy(request => request.Request.RequestString, context => context.Message.Request.RequestString)
.SelectId(context => Guid.NewGuid()));
Event(() => Validating, x => x.CorrelateBy(request => request.Request.RequestString, context => context.Message.Request.RequestString));
Event(() => Interpreting, x => x.CorrelateBy(request => request.Request.RequestString, context => context.Message.Request.RequestString));
Initially(
When(Requesting)
.Then(context =>
{
context.Instance.Request = new Request(context.Data.Request.RequestString);
})
.ThenAsync(context => Console.Out.WriteLineAsync($"Request received: {context.Data.Request.RequestString}"))
.Publish(context => new ValidationNeededEvent(context.Instance))
.TransitionTo(Requested)
);
During(Requested,
When(Validating)
.Then(context =>
{
context.Instance.Request.IsValid = context.Data.Request.IsValid;
if (!context.Data.Request.IsValid)
{
this.TransitionToState(context.Instance, Error);
}
else
{
this.TransitionToState(context.Instance, RequestValid);
}
})
.ThenAsync(context => Console.Out.WriteLineAsync($"Request '{context.Data.Request.RequestString}' validated with {context.Instance.Request.IsValid}"))
.Publish(context => new InterpretationNeededEvent(context.Instance))
,
Ignore(Requesting),
Ignore(Interpreting)
);
During(RequestValid,
When(Interpreting)
.Then((context) =>
{
//do something
})
.ThenAsync(context => Console.Out.WriteLineAsync($"Request '{context.Data.Request.RequestString}' interpreted with {context.Data.Answer}"))
.Publish(context => new AnswerReadyEvent(context.Instance))
.TransitionTo(AnswerReady)
.Finalize(),
Ignore(Requesting),
Ignore(Validating)
);
SetCompletedWhenFinalized();
}
public State Requested { get; private set; }
public State RequestValid { get; private set; }
public State AnswerReady { get; private set; }
public State Error { get; private set; }
//Someone is sending a request to interprete
public Event<IRequesting> Requesting { get; private set; }
//Request is validated
public Event<IValidating> Validating { get; private set; }
//Request is interpreted
public Event<IInterpreting> Interpreting { get; private set; }
class ValidationNeededEvent : IValidationNeeded
{
readonly InterpreterInstance _instance;
public ValidationNeededEvent(InterpreterInstance instance)
{
_instance = instance;
}
public Guid RequestId => _instance.CorrelationId;
public Request Request => _instance.Request;
}
class InterpretationNeededEvent : IInterpretationNeeded
{
readonly InterpreterInstance _instance;
public InterpretationNeededEvent(InterpreterInstance instance)
{
_instance = instance;
}
public Guid RequestId => _instance.CorrelationId;
}
class AnswerReadyEvent : IAnswerReady
{
readonly InterpreterInstance _instance;
public AnswerReadyEvent(InterpreterInstance instance)
{
_instance = instance;
}
public Guid RequestId => _instance.CorrelationId;
}
}
然后我有这样的服务:
public class RequestService : ServiceControl
{
readonly IScheduler scheduler;
IBusControl busControl;
BusHandle busHandle;
InterpreterStateMachine machine;
InMemorySagaRepository<InterpreterInstance> repository;
public RequestService()
{
scheduler = CreateScheduler();
}
public bool Start(HostControl hostControl)
{
Console.WriteLine("Creating bus...");
machine = new InterpreterStateMachine();
repository = new InMemorySagaRepository<InterpreterInstance>();
busControl = Bus.Factory.CreateUsingRabbitMq(x =>
{
IRabbitMqHost host = x.Host(new Uri(/*rabbitMQ server*/), h =>
{
/*credentials*/
});
x.UseInMemoryScheduler();
x.ReceiveEndpoint(host, "interpreting_answer", e =>
{
e.PrefetchCount = 5; //?
e.StateMachineSaga(machine, repository);
});
x.ReceiveEndpoint(host, "2", e =>
{
e.PrefetchCount = 1;
x.UseMessageScheduler(e.InputAddress);
//Scheduling !?
e.Consumer(() => new ScheduleMessageConsumer(scheduler));
e.Consumer(() => new CancelScheduledMessageConsumer(scheduler));
});
});
Console.WriteLine("Starting bus...");
try
{
busHandle = MassTransit.Util.TaskUtil.Await<BusHandle>(() => busControl.StartAsync());
scheduler.JobFactory = new MassTransitJobFactory(busControl);
scheduler.Start();
}
catch (Exception)
{
scheduler.Shutdown();
throw;
}
return true;
}
public bool Stop(HostControl hostControl)
{
Console.WriteLine("Stopping bus...");
scheduler.Standby();
if (busHandle != null) busHandle.Stop();
scheduler.Shutdown();
return true;
}
static IScheduler CreateScheduler()
{
ISchedulerFactory schedulerFactory = new StdSchedulerFactory();
IScheduler scheduler = MassTransit.Util.TaskUtil.Await<IScheduler>(() => schedulerFactory.GetScheduler()); ;
return scheduler;
}
}
我的问题是:
- 如何发送“初始”请求,以便状态机转换到我的初始状态
- 我如何在消费者中“使用react”以检查发送的数据,然后像 1 中那样发送新数据?
最佳答案
好吧,我明白了。我可能遇到了问题,因为我不仅是 Masstransit/Automatonymous 和 RabbitMQ 的新手,而且还没有太多 C# 经验。
因此,如果有人遇到同样的问题,这就是您所需要的: 给定上面的示例,需要三种不同的类型以及一些小接口(interface):
- 发送者(在本例中为“请求者”),包括特定消费者
- 使用特定消息类型(“验证器”和“解释器”)的服务
- 在没有特定消费者的情况下保存状态机的服务
- 一些“契约(Contract)”,它们是定义发送/使用的消息类型的接口(interface)
1) 这是发件人:
using InterpreterStateMachine.Contracts;
using MassTransit;
using System;
using System.Threading.Tasks;
namespace InterpreterStateMachine.Requester
{
class Program
{
private static IBusControl _busControl;
static void Main(string[] args)
{
var busControl = ConfigureBus();
busControl.Start();
Console.WriteLine("Enter request or quit to exit: ");
while (true)
{
Console.Write("> ");
String value = Console.ReadLine();
if ("quit".Equals(value,StringComparison.OrdinalIgnoreCase))
break;
if (value != null)
{
String[] values = value.Split(';');
foreach (String v in values)
{
busControl.Publish<IRequesting>(new
{
Request = new Request(v),
TimeStamp = DateTime.UtcNow
});
}
}
}
busControl.Stop();
}
static IBusControl ConfigureBus()
{
if (null == _busControl)
{
_busControl = Bus.Factory.CreateUsingRabbitMq(cfg =>
{
var host = cfg.Host(new Uri(/*rabbitMQ server*/), h =>
{
/*credentials*/
});
cfg.ReceiveEndpoint(host, "answer_ready", e =>
{
e.Durable = true;
//here the consumer is registered
e.Consumer<AnswerConsumer>();
});
});
_busControl.Start();
}
return _busControl;
}
//here comes the actual logic of the consumer, which consumes a "contract"
class AnswerConsumer : IConsumer<IAnswerReady>
{
public async Task Consume(ConsumeContext<IAnswerReady> context)
{
await Console.Out.WriteLineAsync($"\nReceived Answer for \"{context.Message.Request.RequestString}\": {context.Message.Answer}.");
await Console.Out.WriteAsync(">");
}
}
}
}
2)这是服务(这里是验证服务)
using InterpreterStateMachine.Contracts;
using MassTransit;
using MassTransit.QuartzIntegration;
using MassTransit.RabbitMqTransport;
using Quartz;
using Quartz.Impl;
using System;
using System.Threading.Tasks;
using Topshelf;
namespace InterpreterStateMachine.Validator
{
public class ValidationService : ServiceControl
{
readonly IScheduler _scheduler;
static IBusControl _busControl;
BusHandle _busHandle;
public static IBus Bus => _busControl;
public ValidationService()
{
_scheduler = CreateScheduler();
}
public bool Start(HostControl hostControl)
{
Console.WriteLine("Creating bus...");
_busControl = MassTransit.Bus.Factory.CreateUsingRabbitMq(x =>
{
IRabbitMqHost host = x.Host(new Uri(/*rabbitMQ server*/), h =>
{
/*credentials*/
});
x.UseInMemoryScheduler();
x.UseMessageScheduler(new Uri(RabbitMqServerAddress));
x.ReceiveEndpoint(host, "validation_needed", e =>
{
e.PrefetchCount = 1;
e.Durable = true;
//again this is how the consumer is registered
e.Consumer<RequestConsumer>();
});
});
Console.WriteLine("Starting bus...");
try
{
_busHandle = MassTransit.Util.TaskUtil.Await<BusHandle>(() => _busControl.StartAsync());
_scheduler.JobFactory = new MassTransitJobFactory(_busControl);
_scheduler.Start();
}
catch (Exception)
{
_scheduler.Shutdown();
throw;
}
return true;
}
public bool Stop(HostControl hostControl)
{
Console.WriteLine("Stopping bus...");
_scheduler.Standby();
_busHandle?.Stop();
_scheduler.Shutdown();
return true;
}
static IScheduler CreateScheduler()
{
ISchedulerFactory schedulerFactory = new StdSchedulerFactory();
IScheduler scheduler = MassTransit.Util.TaskUtil.Await<IScheduler>(() => schedulerFactory.GetScheduler());
return scheduler;
}
}
//again here comes the actual consumer logic, look how the message is re-published after it was checked
class RequestConsumer : IConsumer<IValidationNeeded>
{
public async Task Consume(ConsumeContext<IValidationNeeded> context)
{
await Console.Out.WriteLineAsync($"(c) Received {context.Message.Request.RequestString} for validation (Id: {context.Message.RequestId}).");
context.Message.Request.IsValid = context.Message.Request.RequestString.Contains("=");
//send the new message on the "old" context
await context.Publish<IValidating>(new
{
Request = context.Message.Request,
IsValid = context.Message.Request.IsValid,
TimeStamp = DateTime.UtcNow,
RequestId = context.Message.RequestId
});
}
}
}
验证者消费合约“IValidationNeeded”,然后发布合约“IValidating”,然后状态机本身将消费合约(“Validating”事件)。
3) 消费者服务和状态机服务的区别在于“ReceiveEndpoint”。这里没有消费者注册,但是设置了状态机:
...
InterpreterStateMachine _machine = new InterpreterStateMachine();
InMemorySagaRepository<InterpreterInstance> _repository = new InMemorySagaRepository<InterpreterInstance>();
...
x.ReceiveEndpoint(host, "state_machine", e =>
{
e.PrefetchCount = 1;
//here the state machine is set
e.StateMachineSaga(_machine, _repository);
e.Durable = false;
});
4) 最后但同样重要的是,契约(Contract)非常小,看起来像这样:
using System;
namespace InterpreterStateMachine.Contracts
{
public interface IValidationNeeded
{
Guid RequestId { get; }
Request Request { get; }
}
}
总的来说,它非常简单,我只需要动动脑子:D
我希望这会对某人有所帮助。
关于c# - 如何在 C# 中使用 Automatonymous 实现状态机,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/50411172/