Polly 彈性瞬時錯誤處理庫
Polly是一個C#實現的彈性瞬時錯誤處理庫
它可以幫助我們做一些容錯模式處理,比如:
- 超時與重試(Timeout and Retry)
- 熔斷器(Circuit Breaker)
- 艙壁隔離(Bulkhead Isolation)
- 回退(Fallback)
使用也是非常簡單的,比如:
// Retry multiple times, calling an action on each retry
// with the current exception and retry count
Policy
.Handle<SomeExceptionType>()
.Retry(3, onRetry: (exception, retryCount) =>
{
// Add logic to be executed before each retry, such as logging
});
但是每個地方我們都得這樣寫,個人還是不喜,
那麼怎麼簡化呢?
當然是使用 Norns.Urd 這些AOP框架封裝我們常用的東西做成 Attribute
啦
如何實現簡化呢?
我們來嘗試將 Retry功能 做成 RetryAttribute
吧
- 安裝 AOP 框架
自己寫多累呀,用現成的多好呀
dotnet add package Norns.Urd
- 編寫 Retry InterceptorAttribute
public class RetryAttribute : AbstractInterceptorAttribute
{
private readonly int retryCount;
public RetryAttribute(int retryCount)
{
this.retryCount = retryCount;
}
public override async Task InvokeAsync(AspectContext context, AsyncAspectDelegate next)
{
await Policy.Handle<Exception>()
.RetryAsync(retryCount)
.ExecuteAsync(() => next(context));
}
}
- 考慮到 async 和 sync 在Polly 有差異,那麼我們相容一下吧
public class RetryAttribute : AbstractInterceptorAttribute
{
private readonly int retryCount;
public RetryAttribute(int retryCount)
{
this.retryCount = retryCount;
}
public override void Invoke(AspectContext context, AspectDelegate next)
{
Policy.Handle<Exception>()
.Retry(retryCount)
.Execute(() => next(context));
}
public override async Task InvokeAsync(AspectContext context, AsyncAspectDelegate next)
{
await Policy.Handle<Exception>()
.RetryAsync(retryCount)
.ExecuteAsync(() => next(context));
}
}
- 我們來做個測試吧
public class RetryTest
{
public class DoRetryTest
{
public int Count { get; set; }
[Retry(2)] // 使用 Retry
public virtual void Do()
{
if (Count < 50)
{
Count++; // 每呼叫一次就加1
throw new FieldAccessException();
}
}
}
public DoRetryTest Mock()
{
return new ServiceCollection()
.AddTransient<DoRetryTest>()
.ConfigureAop()
.BuildServiceProvider()
.GetRequiredService<DoRetryTest>();
}
[Fact]
public void RetryWhenSync()
{
var sut = Mock();
Assert.Throws<FieldAccessException>(() => sut.Do());
Assert.Equal(3, sut.Count); //我們期望呼叫總共 3 次
}
}
是的,就是這樣,我們可以在任何地方使用 RetryAttribute
當然,一些常見的方法已經封裝在了 Norns.Urd.Extensions.Polly
這裡通過Norns.Urd將Polly的各種功能整合為更加方便使用的功能
如何啟用 Norns.Urd + Polly, 只需使用EnablePolly()
如:
new ServiceCollection()
.AddTransient<DoTimeoutTest>()
.ConfigureAop(i => i.EnablePolly())
TimeoutAttribute
[Timeout(seconds: 1)] // timeout 1 seconds, when timeout will throw TimeoutRejectedException
double Wait(double seconds);
[Timeout(timeSpan: "00:00:00.100")] // timeout 100 milliseconds, only work on async method when no CancellationToken
async Task<double> WaitAsync(double seconds, CancellationToken cancellationToken = default);
[Timeout(timeSpan: "00:00:01")] // timeout 1 seconds, but no work on async method when no CancellationToken
async Task<double> NoCancellationTokenWaitAsync(double seconds);
RetryAttribute
[Retry(retryCount: 2, ExceptionType = typeof(AccessViolationException))] // retry 2 times when if throw Exception
void Do()
CircuitBreakerAttribute
[CircuitBreaker(exceptionsAllowedBeforeBreaking: 3, durationOfBreak: "00:00:01")]
//or
[AdvancedCircuitBreaker(failureThreshold: 0.1, samplingDuration: "00:00:01", minimumThroughput: 3, durationOfBreak: "00:00:01")]
void Do()
BulkheadAttribute
[Bulkhead(maxParallelization: 5, maxQueuingActions: 10)]
void Do()
有關 Norns.Urd, 大家可以檢視 https://fs7744.github.io/Norns.Urd/zh-cn/index.html