Polly是一个.NET弹性和瞬态故障处理库,允许开发人员以流畅和线程安全的方式表达诸如重试,断路器,超时,隔离头和回退之类的策略。
Polly面向.NET Standard 1.1(覆盖范围:.NET Core 1.0,Mono,Xamarin,UWP,WP8.1 +)和.NET Standard 2.0+(覆盖范围:.NET Core 2.0 + 、. NET Core 3.0和更高版本的Mono,Xamarin和UWP目标)。nuget软件包还包括.NET Framework 4.6.1和4.7.2的直接目标。
使用方式
通过NuGet安装
Install-Package Polly
用法
故障处理,响应策略
故障处理策略处理您通过策略执行的委托引发的特定异常或 返回的结果。
步骤1:指定您希望策略处理的异常/错误
// 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)
步骤2:指定策略应如何处理这些故障
2.1、重试
// 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、永远重试(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、等待并重试
// 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 } );
开源地址:
https://github.com/App-vNext/Polly