/// <summary>
/// Simple helper method to set the acquired state and time acquired of a MutexInfo.
/// </summary>
/// <param name="info">The MutexInfo to set the status of</param>
/// <param name="isAcquired">True if the mutex is owned; false otherwise.</param>
private void SetOwned(MutexInfo info, bool isAcquired)
{
info.Attached = isAcquired;
if (isAcquired)
{
info.TimeAcquired = DateTime.Now;
}
_ownedMutexes[info.Name] = info;
}
/// <summary>
/// Releases the specified mutex, if owned.
/// </summary>
/// <param name="name">The name of the mutex to release</param>
public void ReleaseMutex(string name)
{
if (!OwnsMutex(name))
{
return;
}
MutexInfo mutex = _ownedMutexes[name];
this.MemcachedClient.Cas(this.KeyPrefix + mutex.Name, null, mutex.CasToken, 1);
this.SetOwned(mutex, false);
}
/// <summary>
/// Acquires a mutex.
/// </summary>
/// <param name="name">The name of the mutex to acquire</param>
/// <param name="msTimeout">The milliseconds to wait before giving up on acquiring</param>
/// <param name="msLifetime">The maximum length of time the mutex will last after being acquired; -1 for infinity.</param>
/// <returns>True on success, false on failure.</returns>
public bool AcquireMutex(string name, long msTimeout, long msLifetime)
{
if (msLifetime < -1 || msLifetime == 0)
{
throw new ArgumentOutOfRangeException("msLifetime", "msLifetime must be either -1 or a positive integer.");
}
if (OwnsMutex(name))
{
return(true);
}
long memcachedLifetime = (msLifetime == -1) ? 0 : msLifetime; //Memcached requires a lifetime of 0 for infinite-length mutexes
MutexInfo mutex;
if (!_ownedMutexes.ContainsKey(name))
{
mutex = new MutexInfo()
{
Name = name,
Lifetime = msLifetime,
ServerGUID = this.GUID,
};
}
else
{
mutex = _ownedMutexes[name];
mutex.Lifetime = msLifetime;
}
DateTime beganAcquiring = DateTime.Now;
string memcachedKey = this.KeyPrefix + name;
ulong casToken = 0;
while (((DateTime.Now - beganAcquiring).TotalMilliseconds < msTimeout) || msTimeout == -1)
{
object currentOwnerRaw = this.MemcachedClient.Get(memcachedKey, ref casToken);
if (currentOwnerRaw == null)
{
bool setOwner = casToken == 0 ? this.MemcachedClient.Add(memcachedKey, this.GUID, memcachedLifetime)
: this.MemcachedClient.Cas(memcachedKey, this.GUID, casToken, memcachedLifetime);
if (setOwner)
{
ulong newCasToken = 0;
string newOwner = (string)this.MemcachedClient.Get(memcachedKey, ref newCasToken);
if (newOwner == this.GUID)
{
mutex.CasToken = newCasToken;
this.SetOwned(mutex, true);
}
}
}
else
{
string currentOwner = (string)currentOwnerRaw;
if (currentOwner == this.GUID)
{
this.SetOwned(mutex, true);
return(true);
}
}
Thread.Sleep(this.SleepTime);
}
this.SetOwned(mutex, false);
return(false);
}
