第一次重试断路后没有重试

Question

我有以下政策：

var sharedBulkhead = Policy.BulkheadAsync(
            maxParallelization: maxParallelizations, 
            maxQueuingActions: maxQueuingActions,
            onBulkheadRejectedAsync: (context) =>
            {
                Log.Info($"Bulk head rejected => Policy Wrap: {context.PolicyWrapKey}, Policy: {context.PolicyKey}, Endpoint: {context.OperationKey}");
                return TaskHelper.EmptyTask;
            }
        );

var retryPolicy = Policy.Handle<Exception>(e => (e is HttpRequestException)).WaitAndRetryAsync(
            retryCount: maxRetryCount,
            sleepDurationProvider: attempt => TimeSpan.FromSeconds(Math.Pow(2, attempt)),
            onRetryAsync: (exception, calculatedWaitDuration, retryCount, context) =>
            {
                Log.Error($"Retry => Count: {retryCount}, Wait duration: {calculatedWaitDuration}, Policy Wrap: {context.PolicyWrapKey}, Policy: {context.PolicyKey}, Endpoint: {context.OperationKey}, Exception: {exception}.");
                return TaskHelper.EmptyTask;
            });

            var circuitBreaker = Policy.Handle<Exception>(e => (e is HttpRequestException)).CircuitBreakerAsync(
            exceptionsAllowedBeforeBreaking: maxExceptionsBeforeBreaking, 
            durationOfBreak: TimeSpan.FromSeconds(circuitBreakDurationSeconds), 
            onBreak: (exception, timespan, context) =>
            {
                Log.Error($"Circuit broken => Policy Wrap: {context.PolicyWrapKey}, Policy: {context.PolicyKey}, Endpoint: {context.OperationKey}, Exception: {exception}");
            },
            onReset: (context) =>
            {
                Log.Info($"Circuit reset => Policy Wrap: {context.PolicyWrapKey}, Policy: {context.PolicyKey}, Endpoint: {context.OperationKey}");
            }
        );

var fallbackForCircuitBreaker = Policy<bool>
         .Handle<BrokenCircuitException>()
         .FallbackAsync(
             fallbackValue: false,
             onFallbackAsync: (b, context) =>
             {
                 Log.Error($"Operation attempted on broken circuit => Policy Wrap: {context.PolicyWrapKey}, Policy: {context.PolicyKey}, Endpoint: {context.OperationKey}");
                 return TaskHelper.EmptyTask;
             }
         );

var fallbackForAnyException = Policy<bool>
            .Handle<Exception>()
            .FallbackAsync(
                fallbackAction: (ct, context) => { return Task.FromResult(false); },
                onFallbackAsync: (e, context) =>
                {
                    Log.Error($"An unexpected error occured => Policy Wrap: {context.PolicyWrapKey}, Policy: {context.PolicyKey}, Endpoint: {context.OperationKey}");
                    return TaskHelper.EmptyTask;
                }
            );


var resilienceStrategy = Policy.WrapAsync(retryPolicy, circuitBreaker, sharedBulkhead);
        var policyWrap = fallbackForAnyException.WrapAsync(fallbackForCircuitBreaker.WrapAsync(resilienceStrategy));

我这样执行政策：

Task.Run(() =>
        {
            foreach (var changeMessage in changeMessages)
            {
                policyWrap.ExecuteAsync((context) => CallApi(changeMessage), new Context(endPoint));
            }
        });

第一次调用 fallbackForCircuitBreaker 后不会重试。无论电路处于什么状态，我都希望根据等待持续时间进行重试。为什么这不起作用？

Answer 1

No retries happen after the first call to fallbackForCircuitBreaker. I want the retries to happen as per the wait duration regardless of the state the circuit is in.

重试策略未配置为处理 BrokenCircuitException，仅处理 HttpRequestException。

要使重试策略也为 BrokenCircuitException 重试，请配置策略：

var retryPolicy = Policy
    .Handle<HttpRequestException>()
    .Or<BrokenCircuitException>()
    .WaitAndRetryAsync( /* etc */ );

注意：如果只做上面的改动，问题PolicyWrap中贴出的政策顺序：

.., fallbackForCircuitBreaker, retryPolicy, circuitBreaker, sharedBulkhead

将意味着 fallbackForCircuitBreaker 仅在所有重试失败且最后一次重试失败并显示 BrokenCircuitException 时才会被调用。参见 PolicyWrap documentation。

第一次重试断路后没有重试

Retries are not happening after the first retry on a broken circuit

c#

asp.net

polly