public IDistributedLock AcquireLock(string name, TimeSpan?maxValidFor, TimeSpan?timeout)
{
try {
DistributedLock result = AcquireLockInternal(name, maxValidFor, timeout, throwOnTimeout: true);
Logger.Debug("Successfully acquired lock '{0}'.", name);
return(result);
}
catch (Exception ex) {
Logger.Error(ex, "Error while trying to acquire lock '{0}'.", name);
throw;
}
}
private DistributedLock AcquireLockInternal(string name, TimeSpan?maxValidFor, TimeSpan?timeout, bool throwOnTimeout)
{
var internalName = GetInternalLockName(name);
var monitorTimeout = timeout.HasValue ? timeout.Value : TimeSpan.FromMilliseconds(-1); // -1 ms is .NET magic number for "infinite".
var monitorObj = String.Intern(String.Format("{0}:{1}", _applicationEnvironment.GetEnvironmentIdentifier(), internalName));
if (!Monitor.TryEnter(monitorObj, monitorTimeout))
{
Logger.Debug("Could not enter local monitor for lock '{0}' within the specified timeout ({1}).", internalName, timeout);
if (throwOnTimeout)
{
throw new TimeoutException(String.Format("Failed to acquire lock '{0}' within the specified timeout ({1}).", internalName, timeout));
}
return(null);
}
Logger.Debug("Successfully entered local monitor for lock '{0}'.", internalName);
try {
DistributedLock dLock = null;
// If there's already a distributed lock object in our dictionary, that means
// this acquisition is a reentrance. Use the existing lock object from the
// dictionary but increment its count.
if (_locks.TryGetValue(monitorObj, out dLock))
{
Logger.Debug("Current thread is re-entering lock '{0}'; incrementing count.", internalName);
dLock.Increment();
}
else
{
// No distributed lock object existed in our dictionary. Try to take ownership
// of database record until timeout expires, and if successful create a distributed
// lock object and add it to our dictionary.
var success = RepeatUntilTimeout(timeout, _defaultRepeatInterval, () => {
if (EnsureDistributedLockRecord(internalName, maxValidFor))
{
Logger.Debug("Record for lock '{0}' already owned by current machine or was successfully created; creating lock object.", internalName);
dLock = new DistributedLock(name, internalName, releaseLockAction: () => {
Monitor.Exit(monitorObj);
DeleteDistributedLockRecord(internalName);
});
_locks.Add(monitorObj, dLock);
return(true);
}
return(false);
});
if (!success)
{
Logger.Debug("Record for lock '{0}' could not be created for current machine within the specified timeout ({1}).", internalName, timeout);
if (throwOnTimeout)
{
throw new TimeoutException(String.Format("Failed to acquire lock '{0}' within the specified timeout ({1}).", internalName, timeout));
}
return(null);
}
}
return(dLock);
}
catch (Exception ex) {
Monitor.Exit(monitorObj);
Logger.Error(ex, "An error occurred while trying to acquire lock '{0}'.", internalName);
throw;
}
}