动态重试代理答案

【问题标题】：Dynamic retry proxy动态重试代理
【发布时间】：2012-05-08 00:52:26
【问题描述】：

考虑以下，它有效：

public interface IService
{
    void DoSomething(object arg);
    void DoSomethingElse(object arg, bool anotherArg);
    bool AndDoYetMoreStuff(object arg, object[] moreArgs);
}

public class Service : IService
{
    public void DoSomething(object arg){}

    public void DoSomethingElse(object arg, bool anotherArg){}

    public bool AndDoYetMoreStuff(object arg, object[] moreArgs)
    {
        return true;
    }
}

public class ServiceRetryProxy : IService
{
    const int retryLimit = 3;
    private readonly IService _service;

    public ServiceRetryProxy(IService service)
    {
        _service = service;
    }

    private void RetryOnException(Action<IService> ctx)
    {
        ReconnectOnException(service =>
        {
            ctx(service);
            return new object();
        });
    }

    private T RetryOnException<T>(Func<IService, T> ctx)
    {
        var counter = 0;
        Exception lastException = null;
        while (counter < retryLimit)
        {
            try
            {
                return ctx(_service);
            }
            catch (Exception ex)
            {
                lastException = ex;
                counter++;
            }
        }

        throw lastException;
    }

    public void DoSomething(object arg)
    {
        ReconnectOnException(x => x.DoSomething(arg));
    }

    public void DoSomethingElse(object arg, bool anotherArg)
    {
        ReconnectOnException(x => x.DoSomethingElse(arg, anotherArg));
    }

    public bool AndDoYetMoreStuff(object arg, object[] moreArgs)
    {
        return ReconnectOnException(x => x.AndDoYetMoreStuff(arg, moreArgs));
    }
}

这样做的问题是我必须为接口的每个方法编写一个代理方法。我想要一个更“动态”的解决方案，以便我可以将 RetryOnException（或任何其他逻辑）应用于任何给定接口上的每个方法。我目前正在研究 Castle DynamicProxy，但如果有其他选项呢？

【问题讨论】：

标签： c# .net castle-dynamicproxy dynamic-proxy

【解决方案1】：

城堡动态代理当然是一种选择。

但我个人会选择 postsharp： http://www.sharpcrafters.com/

我已经将它用于类似的场景。我创建了 RetryOneexceptionAspect，您可以在其中指定异常类型、重试次数并将其应用于任何方法：

[Serializable]
public class RetryOnExceptionAspect : MethodInterceptionAspect
{
    private readonly int maxRetries;

    private readonly Type exceptionType;

    public RetryOnExceptionAspect(int maxRetries, Type exceptionType)
    {
        this.maxRetries = maxRetries;
        this.exceptionType = exceptionType;
    }

    public override void OnInvoke(MethodInterceptionArgs args)
    {
        for (int i = 0; i < maxRetries + 1; i++)
        {
            try
            {
                args.Proceed();
            }
            catch (Exception e)
            {
                if (e.GetType() == exceptionType && i < maxRetries)
                {
                    continue;
                }

                throw;
            }

            break;
        }
    }
}

用法如下：

public class Service : IService
{
    [RetryOnExceptionAspect(5, typeof(TimeoutException)]
    public void DoSomething()
    {
    }
}

【讨论】：