private MemoryLockStatus TryAcquireResources(MemoryLock memoryLock)
{
//这里可以不加锁，因为已经上了资源锁
long now = TimeUtil.UtcNowUnixTimeMilliseconds;
for (int i = 0; i < memoryLock.ResourceKeys.Count; ++i)
{
string resourceKey = memoryLock.ResourceKeys[i];
//不存在 or 存在但已经过期，因为MemoryCache并不能即使的清除过期，所以也得检查
if (!_memoryCache.TryGetValue(resourceKey, out MemoryLockResourceExpiryInfo storedInfo) || now - storedInfo.Timestamp >= storedInfo.ExpiryMilliseconds)
{
_memoryCache.Set(
resourceKey,
new MemoryLockResourceExpiryInfo(now, (long)memoryLock.ExpiryTime.TotalMilliseconds, memoryLock.ResourceValues[i]),
memoryLock.ExpiryTime);
continue;
}
else
{
//存在且不过期
return(MemoryLockStatus.Failed);
}
}
return(MemoryLockStatus.Acquired);
}
private void ExtendLockLifetime(MemoryLock memoryLock)
{
if (memoryLock.Status != MemoryLockStatus.Acquired)
{
_logger.LogDebug(
"锁已不是获取状态，停止自动延期... {ThreadID}, {ResourceKeys}, {Status}",
Thread.CurrentThread.ManagedThreadId, memoryLock.ResourceKeys, memoryLock.Status);
return;
}
memoryLock.ExtendCount++;
long now = TimeUtil.UtcNowUnixTimeMilliseconds;
for (int i = 0; i < memoryLock.ResourceKeys.Count; ++i)
{
if (_memoryCache.TryGetValue(memoryLock.ResourceKeys[i], out MemoryLockResourceExpiryInfo storedInfo) && storedInfo.ResourceValue == memoryLock.ResourceValues[i])
{
_memoryCache.Set(
memoryLock.ResourceKeys[i],
new MemoryLockResourceExpiryInfo(now, (long)memoryLock.ExpiryTime.TotalMilliseconds, memoryLock.ResourceValues[i]),
memoryLock.ExpiryTime);
}
}
}
internal static void StopKeepAliveTimer(MemoryLock memoryLock)
{
if (memoryLock.KeepAliveTimer != null)
{
memoryLock.KeepAliveTimer.Change(Timeout.Infinite, Timeout.Infinite);
memoryLock.KeepAliveTimer.Dispose();
memoryLock.KeepAliveTimer = null;
}
}
private void StartAutoExtendTimer(MemoryLock memoryLock)
{
long interval = (long)memoryLock.ExpiryTime.TotalMilliseconds / 2;
memoryLock.KeepAliveTimer = new Timer(
state => { ExtendLockLifetime(memoryLock); },
null,
interval,
interval);
}
internal void Unlock(MemoryLock memoryLock)
{
//这里不加锁也没关系，因为不影响上面Acquire时的三个判断
//比如：判断“存在但过期”，这里删掉了。不影响
StopKeepAliveTimer(memoryLock);
for (int i = 0; i < memoryLock.ResourceKeys.Count; ++i)
{
if (_memoryCache.TryGetValue(memoryLock.ResourceKeys[i], out MemoryLockResourceExpiryInfo storedInfo) && storedInfo.ResourceValue == memoryLock.ResourceValues[i])
{
_memoryCache.Remove(memoryLock.ResourceKeys[i]);
}
}
memoryLock.Status = MemoryLockStatus.Disposed;
}
public IMemoryLock Lock(string resourceType, IEnumerable <string> resources, TimeSpan expiryTime, TimeSpan?waitTime = null, CancellationToken cancellationToken = default)
{
if (waitTime == null)
{
waitTime = _options.DefaultWaitTime;
}
MemoryLock memoryLock = new MemoryLock(this, resourceType, resources, expiryTime);
SemaphoreSlim semaphore = _resourceTypeSemaphoreDict.GetOrAdd(resourceType, new SemaphoreSlim(1, 1));
Stopwatch stopwatch = Stopwatch.StartNew();
if (semaphore.Wait(waitTime.Value, cancellationToken))
{
try
{
if (waitTime != TimeSpan.Zero)
{
//可以等待
while (!memoryLock.IsAcquired && stopwatch.Elapsed <= waitTime)
{
memoryLock.Status = TryAcquireResources(memoryLock);
if (!memoryLock.IsAcquired)
{
#pragma warning disable VSTHRD002 // Avoid problematic synchronous waits
Task.Delay(_options.DefaultRetryIntervalMilliseconds, cancellationToken).Wait(cancellationToken);
#pragma warning restore VSTHRD002 // Avoid problematic synchronous waits
}
}
if (!memoryLock.IsAcquired)
{
memoryLock.Status = MemoryLockStatus.Expired;
}
}
else
{
//不等待
memoryLock.Status = TryAcquireResources(memoryLock);
}
}
finally
{
semaphore.Release();
}
if (memoryLock.IsAcquired)
{
StartAutoExtendTimer(memoryLock);
}
}
else
{
memoryLock.Status = MemoryLockStatus.ResourceTypeSemaphoreExpired;
}
stopwatch.Stop();
return(memoryLock);
}
