Re: [milo-dev] Alarm/Event Notifications triggers from OPC server

[Isuru Samaraweera <isuru@xxxxxxxx>]

For instance Alarm/Events might need to be notified to the client as it happens instead of waiting till PublishRequest arrives from a client after frequency is met.

Please clarify.

On Fri, Nov 24, 2017 at 10:45 AM, Isuru Samaraweera <isuru@xxxxxxxx> wrote:

When subscribing to events through subscription we set up  a sampling interval.

If we set the interval as 5 seconds.Event notifications are also sent out to the client in the same frequency by queuing them in the server instead of as soon as event happens.

Is there anyway events notifications are sentout to the client as the event transpires bypassing PublishRequest/Response which happens in the frequency set up during Subscription?

Thanks,

Isuru

On Fri, Nov 24, 2017 at 12:36 AM, Kevin Herron <kevinherron@xxxxxxxxx> wrote:

Subscribing to events work like this, assuming you have a Subscription already:

1. Find the ObjectNode in the server that is the source of events you're interested in. Its EventNotifier attribute will be set.

2. Create a MonitoredItem, pointing at that EventNotifier attribute, in MonitoringMode.Reporting, optionally specifying an EventFilter. How you define an EventFilter is talked about in part 4 of the spec, section 7.17.3. It's almost like you're building a SQL query with a select and where clause that determines what kinds of events and what fields from those events are delivered.

3. Set an EventConsumer on the UaMonitoredItem you created. That will be the callback invoked when the server delivers events that passed the EventFilter.

You shouldn't need to worry about receiving empty PublishResponses or null NotificationMessages (neither of those things should happen, except an empty PublishResponse when its a KeepAlive). If you're using the OpcUaClient then you don't ever interact directly with PublishRequest/PublishResponse in the first place - the subscription manager takes care of that and you just receive callbacks on the items you create.

On Thu, Nov 23, 2017 at 9:44 AM, Isuru Samaraweera <isuru@xxxxxxxx> wrote:

Hi All,

Normal procedure for receiving notification from server is

1.Create Subscription

2.Create MpnitoringParameters/MonitoredItemCreateRequest

3.createMonitoredItems

Once you do this PublishRequest/Response is used to receive notifications.

If we have to receive specific notifications/alarms instead of all the notifications from the server

The right way is to define a filter(DataChangeFilter,EventFilter etc) of type Extensible Parameter MonitoringFilter along with above 3 steps and

sentout notifications only if filter criteria is met?

If criteria is not met PublishResponse will be sent out with NotificationMessage set to null?

Or Is there a different way for condtionalNotifications/Alarms to be sent out without creating subscriptions,filters and monitoreditems and without sending empty PublishResponses ?

Please clarify.

Thanks,

Isuru

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