SqlClient 中可設定的重試邏輯核心 API

發行項
05/23/2023

適用於：.NET Framework .NET .NET Standard

下載 ADO.NET

如果內建重試邏輯提供者未涵蓋您的需求，您可以建立自己的自訂提供者。然後，您可以將這些提供者指派給 SqlConnection 或 SqlCommand 物件，以套用您的自訂邏輯。

內建提供者是針對可用來實作自訂提供者的三個介面所設計。接著就可以在 SqlConnection 或 SqlCommand 上，透過與內部重試提供者相同的方式來使用自訂重試提供者:

SqlRetryIntervalBaseEnumerator：產生時間間隔序列。
SqlRetryLogicBase：如果尚未超過重試次數且符合暫時性狀況，則擷取指定列舉值的下一個時間間隔。
SqlRetryLogicBaseProvider：將重試邏輯套用至連線和命令作業。

警告

透過實作自訂重試邏輯提供者，您就可以掌控所有層面，包括並行、效能和例外狀況管理。

範例

此範例中的實作將盡可能簡單，以便逐步示範自訂。不會包含執行緒安全性、非同步和並行等進階實務。若要深入了解實際實作，您可以研究 Microsoft.Data.SqlClient GitHub 存放庫 (英文) 中預先定義的重試邏輯。

定義可設定的自訂重試邏輯類別：

列舉值：定義固定的時間間隔序列，並將可接受的時間範圍從兩分鐘延長到四分鐘。

public class CustomEnumerator : SqlRetryIntervalBaseEnumerator
{
    // Set the maximum acceptable time to 4 minutes
    private readonly TimeSpan _maxValue = TimeSpan.FromMinutes(4);

    public CustomEnumerator(TimeSpan timeInterval, TimeSpan maxTime, TimeSpan minTime)
        : base(timeInterval, maxTime, minTime) {}

    // Return fixed time on each request
    protected override TimeSpan GetNextInterval()
    {
        return GapTimeInterval;
    }

    // Override the validate method with the new time range validation
    protected override void Validate(TimeSpan timeInterval, TimeSpan maxTimeInterval, TimeSpan minTimeInterval)
    {
        if (minTimeInterval < TimeSpan.Zero || minTimeInterval > _maxValue)
        {
            throw new ArgumentOutOfRangeException(nameof(minTimeInterval));
        }

        if (maxTimeInterval < TimeSpan.Zero || maxTimeInterval > _maxValue)
        {
            throw new ArgumentOutOfRangeException(nameof(maxTimeInterval));
        }

        if (timeInterval < TimeSpan.Zero || timeInterval > _maxValue)
        {
            throw new ArgumentOutOfRangeException(nameof(timeInterval));
        }

        if (maxTimeInterval < minTimeInterval)
        {
            throw new ArgumentOutOfRangeException(nameof(minTimeInterval));
        }
    }
}

重試邏輯：在任何不屬於使用中交易的命令上實作重試邏輯。將重試次數從 60 降到 20。

public class CustomRetryLogic : SqlRetryLogicBase
{
    // Maximum number of attempts
    private const int maxAttempts = 20;

    public CustomRetryLogic(int numberOfTries,
                             SqlRetryIntervalBaseEnumerator enumerator,
                             Predicate<Exception> transientPredicate)
    {
        if (!(numberOfTries > 0 && numberOfTries <= maxAttempts))
        {
            // 'numberOfTries' should be between 1 and 20.
            throw new ArgumentOutOfRangeException(nameof(numberOfTries));
        }

        // Assign parameters to the relevant properties
        NumberOfTries = numberOfTries;
        RetryIntervalEnumerator = enumerator;
        TransientPredicate = transientPredicate;
        Current = 0;
    }

    // Prepare this object for the next round
    public override void Reset()
    {
        Current = 0;
        RetryIntervalEnumerator.Reset();
    }

    public override bool TryNextInterval(out TimeSpan intervalTime)
    {
        intervalTime = TimeSpan.Zero;
        // First try has occurred before starting the retry process. 
        // Check if retry is still allowed
        bool result = Current < NumberOfTries - 1;

        if (result)
        {
            // Increase the number of attempts
            Current++;
            // It's okay if the RetryIntervalEnumerator gets to the last value before we've reached our maximum number of attempts.
            // MoveNext() will simply leave the enumerator on the final interval value and we will repeat that for the final attempts.
            RetryIntervalEnumerator.MoveNext();
            // Receive the current time from enumerator
            intervalTime = RetryIntervalEnumerator.Current;
        }
        return result;
    }
}

提供者：實作重試提供者，以在同步作業上重試，而不需要 Retrying 事件。將 TimeoutException 新增至現有的 SqlException 暫時性例外狀況錯誤號碼。

public class CustomProvider : SqlRetryLogicBaseProvider
{
    // Preserve the given retryLogic on creation
    public CustomProvider(SqlRetryLogicBase retryLogic)
    {
        RetryLogic = retryLogic;
    }

    public override TResult Execute<TResult>(object sender, Func<TResult> function)
    {
        // Create a list to save transient exceptions to report later if necessary
        IList<Exception> exceptions = new List<Exception>();
        // Prepare it before reusing
        RetryLogic.Reset();
        // Create an infinite loop to attempt the defined maximum number of tries
        do
        {
            try
            {
                // Try to invoke the function
                return function.Invoke();
            }
            // Catch any type of exception for further investigation
            catch (Exception e)
            {
                // Ask the RetryLogic object if this exception is a transient error
                if (RetryLogic.TransientPredicate(e))
                {
                    // Add the exception to the list of exceptions we've retried on
                    exceptions.Add(e);
                    // Ask the RetryLogic for the next delay time before the next attempt to run the function
                    if (RetryLogic.TryNextInterval(out TimeSpan gapTime))
                    {
                        Console.WriteLine($"Wait for {gapTime} before next try");
                        // Wait before next attempt
                        Thread.Sleep(gapTime);
                    }
                    else
                    {
                        // Number of attempts has exceeded the maximum number of tries
                        throw new AggregateException("The number of retries has exceeded the maximum number of attempts.", exceptions);
                    }
                }
                else
                {
                    // If the exception wasn't a transient failure throw the original exception
                    throw;
                }
            }
        } while (true);
    }

    public override Task<TResult> ExecuteAsync<TResult>(object sender, Func<Task<TResult>> function, CancellationToken cancellationToken = default)
    {
        throw new NotImplementedException();
    }

    public override Task ExecuteAsync(object sender, Func<Task> function, CancellationToken cancellationToken = default)
    {
        throw new NotImplementedException();
    }
}

建立包含已定義自訂類型的重試提供者執行個體：

public static SqlRetryLogicBaseProvider CreateCustomProvider(SqlRetryLogicOption options)
{
    // 1. create an enumerator instance
    CustomEnumerator customEnumerator = new CustomEnumerator(options.DeltaTime, options.MaxTimeInterval, options.MinTimeInterval);
    // 2. Use the enumerator object to create a new RetryLogic instance
    CustomRetryLogic customRetryLogic = new CustomRetryLogic(5, customEnumerator, (e) => TransientErrorsCondition(e, options.TransientErrors));
    // 3. Create a provider using the RetryLogic object
    CustomProvider customProvider = new CustomProvider(customRetryLogic);
    return customProvider;
}

下列函數會使用指定的可重試例外狀況清單和特殊 TimeoutException 例外狀況來評估例外狀況，以判斷其是否可重試：

// Return true if the exception is a transient fault.
private static bool TransientErrorsCondition(Exception e, IEnumerable<int> retriableConditions)
{
    bool result = false;

    // Assess only SqlExceptions
    if (retriableConditions != null && e is SqlException ex)
    {
        foreach (SqlError item in ex.Errors)
        {
            // Check each error number to see if it is a retriable error number
            if (retriableConditions.Contains(item.Number))
            {
                result = true;
                break;
            }
        }
    }
    // Other types of exceptions can also be assessed
    else if (e is TimeoutException)
    {
        result = true;
    }
    return result;
}

使用自訂的重試邏輯：

定義重試邏輯參數：

// Define the retry logic parameters
var options = new SqlRetryLogicOption()
{
    // Tries 5 times before throwing an exception
    NumberOfTries = 5,
    // Preferred gap time to delay before retry
    DeltaTime = TimeSpan.FromSeconds(1),
    // Maximum gap time for each delay time before retry
    MaxTimeInterval = TimeSpan.FromSeconds(20),
    // SqlException retriable error numbers
    TransientErrors = new int[] { 4060, 1024, 1025}
};

建立自訂重試提供者：

// Create a custom retry logic provider
SqlRetryLogicBaseProvider provider = CustomRetry.CreateCustomProvider(options);

將重試提供者指派給 SqlConnection.RetryLogicProvider 或 SqlCommand.RetryLogicProvider：

// Assumes that connection is a valid SqlConnection object 
// Set the retry logic provider on the connection instance
connection.RetryLogicProvider = provider;
// Establishing the connection will trigger retry if one of the given transient failure occurs.
connection.Open();

注意

使用之前，別忘了啟用可設定的重試邏輯參數。如需詳細資訊，請參閱啟用可設定的重試邏輯。

共用方式為

SqlClient 中可設定的重試邏輯核心 API

範例

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其他資源