背景

Polly是一個.NET彈性和瞬態故障處理庫，允許開發人員以流暢和線程安全的方式表達諸如重試，斷路器，超時，隔離頭和回退之類的策略。

Polly面向.NET Standard 1.1（覆蓋范圍：.NET Core 1.0，Mono，Xamarin，UWP，WP8.1 +）和.NET Standard 2.0+（覆蓋范圍：.NET Core 2.0 + 、. NET Core 3.0和更高版本的Mono，Xamarin和UWP目標）。nuget軟件包還包括.NET Framework 4.6.1和4.7.2的直接目標。

使用方式

通過NuGet安裝

Install-Package Polly

代碼實現

故障處理，響應策略

故障處理策略處理您通過策略執行的委托引發的特定異?；? ? ? ? ? 返回的結果。

? 步驟1：指定您希望策略處理的異常/錯誤

// Single exception type Policy.Handle<HttpRequestException>()// Single exception type with condition Policy.Handle<SqlException>(ex => ex.Number == 1205)// Multiple exception types Policy.Handle<HttpRequestException>().Or<OperationCanceledException>()// Multiple exception types with condition Policy.Handle<SqlException>(ex => ex.Number == 1205).Or<ArgumentException>(ex => ex.ParamName == "example")// Inner exceptions of ordinary exceptions or AggregateException, with or without conditions // (HandleInner matches exceptions at both the top-level and inner exceptions) Policy.HandleInner<HttpRequestException>().OrInner<OperationCanceledException>(ex => ex.CancellationToken != myToken)

步驟2：指定策略應如何處理這些故障

2.1、重試

?

// Retry once Policy.Handle<SomeExceptionType>().Retry()// Retry multiple times Policy.Handle<SomeExceptionType>().Retry(3)// 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});// Retry multiple times, calling an action on each retry // with the current exception, retry count and context // provided to Execute() Policy.Handle<SomeExceptionType>().Retry(3, onRetry: (exception, retryCount, context) =>{// Add logic to be executed before each retry, such as logging });

2.2、永遠重試（直到成功）

// Retry forever Policy.Handle<SomeExceptionType>().RetryForever()// Retry forever, calling an action on each retry with the // current exception Policy.Handle<SomeExceptionType>().RetryForever(onRetry: exception =>{// Add logic to be executed before each retry, such as logging });// Retry forever, calling an action on each retry with the // current exception and context provided to Execute() Policy.Handle<SomeExceptionType>().RetryForever(onRetry: (exception, context) =>{// Add logic to be executed before each retry, such as logging });

2.3、等待并重試

// Retry, waiting a specified duration between each retry. // (The wait is imposed on catching the failure, before making the next try.) Policy.Handle<SomeExceptionType>().WaitAndRetry(new[]{TimeSpan.FromSeconds(1),TimeSpan.FromSeconds(2),TimeSpan.FromSeconds(3)});// Retry, waiting a specified duration between each retry, // calling an action on each retry with the current exception // and duration Policy.Handle<SomeExceptionType>().WaitAndRetry(new[]{TimeSpan.FromSeconds(1),TimeSpan.FromSeconds(2),TimeSpan.FromSeconds(3)}, (exception, timeSpan) => {// Add logic to be executed before each retry, such as logging }); // Retry, waiting a specified duration between each retry, // calling an action on each retry with the current exception, // duration and context provided to Execute() Policy.Handle<SomeExceptionType>().WaitAndRetry(new[]{TimeSpan.FromSeconds(1),TimeSpan.FromSeconds(2),TimeSpan.FromSeconds(3)}, (exception, timeSpan, context) => {// Add logic to be executed before each retry, such as logging });// Retry, waiting a specified duration between each retry, // calling an action on each retry with the current exception, // duration, retry count, and context provided to Execute() Policy.Handle<SomeExceptionType>().WaitAndRetry(new[]{TimeSpan.FromSeconds(1),TimeSpan.FromSeconds(2),TimeSpan.FromSeconds(3)}, (exception, timeSpan, retryCount, context) => {// Add logic to be executed before each retry, such as logging });// Retry a specified number of times, using a function to // calculate the duration to wait between retries based on // the current retry attempt (allows for exponential backoff) // In this case will wait for // 2 ^ 1 = 2 seconds then // 2 ^ 2 = 4 seconds then // 2 ^ 3 = 8 seconds then // 2 ^ 4 = 16 seconds then // 2 ^ 5 = 32 seconds Policy.Handle<SomeExceptionType>().WaitAndRetry(5, retryAttempt => TimeSpan.FromSeconds(Math.Pow(2, retryAttempt)) );// Retry a specified number of times, using a function to // calculate the duration to wait between retries based on // the current retry attempt, calling an action on each retry // with the current exception, duration and context provided // to Execute() Policy.Handle<SomeExceptionType>().WaitAndRetry(5, retryAttempt => TimeSpan.FromSeconds(Math.Pow(2, retryAttempt)), (exception, timeSpan, context) => {// Add logic to be executed before each retry, such as logging});// Retry a specified number of times, using a function to // calculate the duration to wait between retries based on // the current retry attempt, calling an action on each retry // with the current exception, duration, retry count, and context // provided to Execute() Policy.Handle<SomeExceptionType>().WaitAndRetry(5, retryAttempt => TimeSpan.FromSeconds(Math.Pow(2, retryAttempt)), (exception, timeSpan, retryCount, context) => {// Add logic to be executed before each retry, such as logging});

開源地址

https://github.com/App-vNext/Polly

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