/// <summary>
/// Creates a new set of monitored items for a set of variables.
/// </summary>
/// <remarks>
/// This method only handles data change subscriptions. Event subscriptions are created by the SDK.
/// </remarks>
protected override ServiceResult CreateMonitoredItem(ServerSystemContext context, NodeHandle handle, uint subscriptionId, double publishingInterval, DiagnosticsMasks diagnosticsMasks, TimestampsToReturn timestampsToReturn, MonitoredItemCreateRequest itemToCreate, ref long globalIdCounter, out MonitoringFilterResult filterResult, out IMonitoredItem monitoredItem)
{
filterResult = null;
monitoredItem = null;
// validate parameters.
MonitoringParameters parameters = itemToCreate.RequestedParameters;
// validate attribute.
if (!Attributes.IsValid(handle.Node.NodeClass, itemToCreate.ItemToMonitor.AttributeId))
{
return StatusCodes.BadAttributeIdInvalid;
}
NodeState cachedNode = AddNodeToComponentCache(context, handle, handle.Node);
// check if the node is already being monitored.
MonitoredNode2 monitoredNode = null;
if (!MonitoredNodes.TryGetValue(handle.Node.NodeId, out monitoredNode))
{
MonitoredNodes[handle.Node.NodeId] = monitoredNode = new MonitoredNode2(this, cachedNode);
}
handle.Node = monitoredNode.Node;
handle.MonitoredNode = monitoredNode;
// create a globally unique identifier.
uint monitoredItemId = Utils.IncrementIdentifier(ref globalIdCounter);
// determine the sampling interval.
double samplingInterval = itemToCreate.RequestedParameters.SamplingInterval;
if (samplingInterval < 0)
{
samplingInterval = publishingInterval;
}
// ensure minimum sampling interval is not exceeded.
if (itemToCreate.ItemToMonitor.AttributeId == Attributes.Value)
{
BaseVariableState variable = handle.Node as BaseVariableState;
if (variable != null && samplingInterval < variable.MinimumSamplingInterval)
{
samplingInterval = variable.MinimumSamplingInterval;
}
}
// put a large upper limit on sampling.
if (samplingInterval == Double.MaxValue)
{
samplingInterval = 365 * 24 * 3600 * 1000.0;
}
// put an upper limit on queue size.
uint queueSize = itemToCreate.RequestedParameters.QueueSize;
if (queueSize > MaxQueueSize)
{
queueSize = MaxQueueSize;
}
// validate the monitoring filter.
Range euRange = null;
MonitoringFilter filterToUse = null;
ServiceResult error = ValidateMonitoringFilter(
context,
handle,
itemToCreate.ItemToMonitor.AttributeId,
samplingInterval,
queueSize,
parameters.Filter,
out filterToUse,
out euRange,
out filterResult);
if (ServiceResult.IsBad(error))
{
return error;
}
// create the item.
MonitoredItem datachangeItem = new ComMonitoredItem(
Server,
this,
handle,
subscriptionId,
monitoredItemId,
context.OperationContext.Session,
itemToCreate.ItemToMonitor,
diagnosticsMasks,
timestampsToReturn,
itemToCreate.MonitoringMode,
itemToCreate.RequestedParameters.ClientHandle,
filterToUse,
filterToUse,
euRange,
samplingInterval,
queueSize,
itemToCreate.RequestedParameters.DiscardOldest,
0);
// report the initial value.
ReadInitialValue(context, handle, datachangeItem);
// update monitored item list.
monitoredItem = datachangeItem;
// save the monitored item.
MonitoredItems.Add(monitoredItemId, datachangeItem);
monitoredNode.Add(datachangeItem);
// report change.
OnMonitoredItemCreated(context, handle, datachangeItem);
return error;
}
/// <summary>
/// Called after subscribing/unsubscribing to events.
/// </summary>
/// <param name="context">The context.</param>
/// <param name="monitoredNode">The monitored node.</param>
/// <param name="unsubscribe">if set to <c>true</c> unsubscribing.</param>
protected virtual void OnSubscribeToEvents(
ServerSystemContext context,
MonitoredNode2 monitoredNode,
bool unsubscribe)
{
// defined by the sub-class
}
/// <summary>
/// Returns true if the system must be scanning to provide updates for the monitored item.
/// </summary>
private bool SystemScanRequired(MonitoredNode2 monitoredNode, IDataChangeMonitoredItem2 monitoredItem)
{
// ingore other types of monitored items.
if (monitoredItem == null)
{
return false;
}
// only care about variables.
BaseDataVariableState source = monitoredNode.Node as BaseDataVariableState;
if (source == null)
{
return false;
}
// check for variables that need to be scanned.
if (monitoredItem.AttributeId == Attributes.Value)
{
TestDataObjectState test = source.Parent as TestDataObjectState;
if (test != null && test.SimulationActive.Value)
{
return true;
}
}
return false;
}
/// <summary>
/// Subscribes to events.
/// </summary>
/// <param name="context">The context.</param>
/// <param name="source">The source.</param>
/// <param name="monitoredItem">The monitored item.</param>
/// <param name="unsubscribe">if set to <c>true</c> [unsubscribe].</param>
/// <returns>Any error code.</returns>
protected virtual ServiceResult SubscribeToEvents(
ServerSystemContext context,
NodeState source,
IEventMonitoredItem monitoredItem,
bool unsubscribe)
{
MonitoredNode2 monitoredNode = null;
// handle unsubscribe.
if (unsubscribe)
{
// check for existing monitored node.
if (!MonitoredNodes.TryGetValue(source.NodeId, out monitoredNode))
{
return StatusCodes.BadNodeIdUnknown;
}
monitoredNode.Remove(monitoredItem);
// check if node is no longer being monitored.
if (!monitoredNode.HasMonitoredItems)
{
MonitoredNodes.Remove(source.NodeId);
}
// update flag.
source.SetAreEventsMonitored(context, !unsubscribe, true);
// call subclass.
OnSubscribeToEvents(context, monitoredNode, unsubscribe);
// all done.
return ServiceResult.Good;
}
// only objects or views can be subscribed to.
BaseObjectState instance = source as BaseObjectState;
if (instance == null || (instance.EventNotifier & EventNotifiers.SubscribeToEvents) == 0)
{
ViewState view = source as ViewState;
if (view == null || (view.EventNotifier & EventNotifiers.SubscribeToEvents) == 0)
{
return StatusCodes.BadNotSupported;
}
}
// check for existing monitored node.
if (!MonitoredNodes.TryGetValue(source.NodeId, out monitoredNode))
{
MonitoredNodes[source.NodeId] = monitoredNode = new MonitoredNode2(this, source);
}
// this links the node to specified monitored item and ensures all events
// reported by the node are added to the monitored item's queue.
monitoredNode.Add(monitoredItem);
// This call recursively updates a reference count all nodes in the notifier
// hierarchy below the area. Sources with a reference count of 0 do not have
// any active subscriptions so they do not need to report events.
source.SetAreEventsMonitored(context, !unsubscribe, true);
// signal update.
OnSubscribeToEvents(context, monitoredNode, unsubscribe);
// all done.
return ServiceResult.Good;
}
