惰性超时解决方案断路器抛出 ArgumentOutOfRangeException

发布于 2024-08-17 20:08:09 字数 1206 浏览 4 评论 0原文

Ayende 发布了修改到 Davy Brion 的断路器，其中他更改了超时解决惰性模型的问题。

private readonly DateTime expiry;

public OpenState(CircuitBreaker outer)
    : base(outer)
{
    expiry = DateTime.UtcNow + outer.timeout;
}

public override void ProtectedCodeIsAboutToBeCalled()
{
    if(DateTime.UtcNow < expiry)
        throw new OpenCircuitException();

    outer.MoveToHalfOpenState();
}

但是，构造函数可能会失败，因为 TimeSpan 可以快速溢出 日期时间。例如，当断路器的超时时间是TimeSpan的最大值时。

System.ArgumentOutOfRangeException 被捕获
Message="添加或减去的值会导致无法表示的日期时间。"
...
在 System.DateTime.op_Addition(DateTime d, TimeSpan t)

我们如何避免这个问题并保持预期的行为？

原文

Ayende posted a modification to Davy Brion's circuit breaker, wherein he changed the timeout resolution to a lazy model.

private readonly DateTime expiry;

public OpenState(CircuitBreaker outer)
    : base(outer)
{
    expiry = DateTime.UtcNow + outer.timeout;
}

public override void ProtectedCodeIsAboutToBeCalled()
{
    if(DateTime.UtcNow < expiry)
        throw new OpenCircuitException();

    outer.MoveToHalfOpenState();
}

However, the constructor can fail because a TimeSpan can quickly overflow the maximum value of a DateTime. For example, when the circuit breaker’s timeout is the maximum value of a TimeSpan.

System.ArgumentOutOfRangeException was caught
Message="The added or subtracted value results in an un-representable DateTime."
...
at System.DateTime.op_Addition(DateTime d, TimeSpan t)

How do we avoid this problem and maintain the expected behavior?

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勿忘初心 2024-08-24 20:08:09

做一点数学计算

确定超时是否大于DateTime 的最大值和当前DateTime 的余数。最大TimeSpan通常表示功能上的无限超时（使其成为“一次性”断路器）。

public OpenState(CircuitBreaker outer)
    : base(outer)
{
    DateTime now = DateTime.UtcNow;
    expiry = outer.Timeout > (DateTime.MaxValue - now) 
        ? DateTime.MaxValue
        : now + outer.Timeout;
}

Do a little bit of math

Determine if the timeout is greater than the remainder of the maximum value of a DateTime and the current DateTime. A maximum TimeSpan usually indicates a functionally infinite timeout (making this a "one-time" circuit breaker).

public OpenState(CircuitBreaker outer)
    : base(outer)
{
    DateTime now = DateTime.UtcNow;
    expiry = outer.Timeout > (DateTime.MaxValue - now) 
        ? DateTime.MaxValue
        : now + outer.Timeout;
}

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