public IDatabaseConnectionMonitoringHandle GetMonitoringHandle()
{
lock (this.Lock)
{
// Since this will be called via non-thread-safe paths, we do a true
// dispose check. This error should never reach callers unless they are
// using non-thread-safe stuff concurrently
if (this._state == State.Disposed)
{
throw new ObjectDisposedException(this.GetType().ToString());
}
// If the connection is already closed, we'll never see a state change
// event for the close so just return an already canceled handle
if (this._state == State.AutoStopped || this._state == State.Stopped)
{
return(new AlreadyCanceledHandle());
}
// If the connection does not support state monitoring, we can't produce
// a monitoring handle
if (this._stateChangedHandler == null)
{
return(NullHandle.Instance);
}
var hadRegisteredMonitoringHandles = this.HasRegisteredMonitoringHandlesNoLock;
var connectionLostTokenSource = new CancellationTokenSource();
var handle = new MonitoringHandle(this, connectionLostTokenSource.Token);
(this._monitoringHandleRegistrations ??= new Dictionary <MonitoringHandle, CancellationTokenSource>())
.Add(handle, connectionLostTokenSource);
if (!this.StartMonitorWorkerIfNeededNoLock() &&
!hadRegisteredMonitoringHandles &&
this._state == State.Active)
{
// If we get here, it means we already had an active worker which was not monitoring (doing
// keepalive). That worker is likely asleep, so we fire state changed to wake it up and have it
// switch over to monitoring
this.FireStateChangedNoLock();
}
return(handle);
}
}
private void ReleaseMonitoringHandle(MonitoringHandle handle)
{
lock (this.Lock)
{
if (this._monitoringHandleRegistrations !.TryGetValue(handle, out var cancellationTokenSource))
{
this._monitoringHandleRegistrations.Remove(handle);
cancellationTokenSource.Dispose();
// If we've removed the last reason to be monitoring, fire state changed to stop the monitoring process.
// Without this, the next query that attempts to acquire the connection lock will not think we are monitoring
// and therefore will not fire state change. Then, it will get stuck waiting for the monitoring query to complete
if (this._monitoringHandleRegistrations.Count == 0 && this._state == State.Active)
{
this.FireStateChangedNoLock();
}
}
}
}