StackExchange.Redis - best way to wait for a lock - redis

Question

I have the following method that waits for an exclusive lock on a Redis key. This method works but I'm wondering if there is a better way without a for loop and a Thread.Sleep.
/// <summary>
/// wait up to 2 seconds to achieve a lock!
/// The lock is good for a maximum of 3 seconds
/// </summary>
/// <param name="codeID"></param>
internal void WaitForSingleUseLock(CodeID codeID)
{
var key = _redemptionRepo.SingleUseCodeLockPrefix + codeID.Value;
var expiration = TimeSpan.FromSeconds(3);
for (var i = 0; i < 20; i++)
{
var lockAchieved = _cacheRepo.LockTake(key, "1", expiration);
if (lockAchieved)
{
break;
}
Thread.Sleep(TimeSpan.FromMilliseconds(100));
}
}

Answer 1

The only thing I could suggest different would be to consider pub/sub as a side channel (meaning: in addition, not replacement) for indicating when the lock might now be available - i.e. publish when releasing, and use the sub to release a timer (via a monitor or an async-wait-handle).
Other than that: nope. Redis doesn't have the idea of a pending queue. You could perhaps possibly construct one using lists, but...

Answer 2

After taking #Marc's comments into consideration and meeting with my team about the benefits of Task.Delay() over Thread.Sleep() in this context I decided on this as a final solution:
/// <summary>
/// wait up to 3 seconds to achieve a lock!
/// The lock is good for a maximum of 3 seconds
///
/// Returns the total amount of time until the lock was taken
/// </summary>
internal virtual async Task<TimeSpan> WaitForSingleUseLock(CodeID codeID)
{
var key = _redemptionRepo.SingleUseCodeLockPrefix + codeID.Value;
var totalTime = TimeSpan.Zero;
var maxTime = TimeSpan.FromSeconds(3);
var expiration = TimeSpan.FromSeconds(3);
var sleepTime = TimeSpan.FromMilliseconds(50);
var lockAchieved = false;
while (!lockAchieved && totalTime < maxTime)
{
lockAchieved = _cacheRepo.LockTake(key, "1", expiration);
if (lockAchieved)
{
continue;
}
await Task.Delay(sleepTime);
totalTime += sleepTime;
}
return totalTime;
}