When to refresh the binding on a table edited by multiple-clients?

Transistor · February 20, 2021, 4:28pm

I’ve got a simple configurations table in my Perspective application. It’s used to populate various dropdowns in other views. Multiple users can edit the table. It seems to me …

I don’t want a polling binding to the database as it’s wasteful.
I want to keep the user in the same pager page and on the same selected row. The binding refresh would have to respect that.
I should indicate to the user that the data has been changed and, perhaps, give the opportunity to refresh by button.

How do others manage this? Do I create a memory tag to log the last update time and bind the refresh button’s visibility to that?

Any ideas?

bmusson · February 20, 2021, 4:55pm

Sounds like a job for message handlers.
When a client saves changes, a message is sent to all other clients informing them a change has taken place. Then you can either refresh the table automatically or prompt the user to manually refresh.

Transistor · February 20, 2021, 6:29pm

OK. I’ll read up on those. I’ve watched the video so I should be able to figure it out.

Thanks.

Transistor · February 21, 2021, 12:27pm

I can't get this to work reliably. (I thought I saw it work once between a Chrome and Edge browser on the one PC.)

Here's the sendMessage in my table's onEditCellCommit script:

			msg = system.util.sendMessage(
				project = system.project.getProjectName(),
				messageHandler = 'configUpdate', 
				payload = {'table': 'config'}, 
				scope = "C"
			)

Here's the Edit Message Handler to set my table refresh button's visibility. It's on the button's Message Handlers configUpdate script.

def onMessageReceived(self, payload):
	system.perspective.print('configUpdate message received')
	if payload.has_key('table'):
		if payload['table'] == 'config':    # Corrected after code_skin's comment.
			self.meta.visible = True
			system.perspective.print('Refresh visible')

I have the Listen Scopes set to Session + Page + View in an attempt to get it to work. The message handler is not firing on update of the table cell.

Can anyone clarify what settings I require to sendMessage all active clients that the table has been update?

What scope should be specified in the sendMessage?
What scope should be specified in the message handler?

Update: When I print the msg variable I get the following which I suspect is one of our guys using the Vision client version of the application. I don't see any sign of me using the Perspective version.

[type=Client,sessionId=D292FDD2,clientAddress=10.X.X.X,clientHostName=UsersHostname, project=MyProject,messageHandler=configUpdate,filterParams={userRoles=, scope=C, userZones=},sendStatus=SENT]

Many thanks.

code_skin · February 21, 2021, 12:36pm

This might be an issue.

Try:
if payload['table'] == 'config':

Transistor · February 21, 2021, 12:48pm

Oops! Thanks. I’ve fixed that but the event isn’t being called. I have system.perspective.print statements before that and they don’t execute.

Can you spot anything with my scoping?

Thanks!

code_skin · February 21, 2021, 12:53pm

~~This looks wrong too. try changing this to system.util.getProjectName()~~
nvm.

code_skin · February 21, 2021, 12:56pm

Yes, what is scope='C' ?

You need to specify perspective scopes here; session, page, or view

String scope - The scope that the message should be delivered to. Valid values are "session", "page", or "view". If omitted, "page" will be used. [optional]

https://docs.inductiveautomation.com/display/DOC81/system.perspective.sendMessage

Transistor · February 21, 2021, 1:04pm

They seemed to use shorthand 'S', 'C' or 'G' (gateway) somewhere in the documentation. I've changed to 'session' and the returned value from sendMessage is

[type=Session,sessionId=5a8074b9-acde-4b50-b52f-c17380322f84,
project=MyProject,
messageHandler=configUpdate,
filterParams={userRoles=, scope=session, userZones=},
isRequest=no,
sendStatus=SENT,
type=Session,
sessionId=dbf2304c-01bf-4ffa-b3fd-5aba862d7341,
project=MyProject,
messageHandler=configUpdate,
filterParams={userRoles=, scope=session, userZones=},
isRequest=no,
sendStatus=SENT]

Am I right in thinking that I can send directly from one client to all the others? I don't need to send it to the gateway and have it broadcast it, do I?

code_skin · February 21, 2021, 1:17pm

Oh. I think you want to use system.perspective.sendMessage and not util.sendMessage. they are different.

pturmel · February 21, 2021, 1:19pm

You are confusing system.util.sendMessage with system.perspective.sendMessage. In this case, if all editing is done in Perspective, sending to Perspective’s session scope should be the right answer.

pturmel · February 21, 2021, 1:21pm

Perspective scripts are already running in the gateway.

Transistor · February 21, 2021, 1:23pm

Doesn't system.perspective.sendMessage only send the the client the code is triggered from.

Send a message to a message handler within the same session. system.perspective.sendMessage.

I want to notify all clients that the table has been updated.

pturmel · February 21, 2021, 1:25pm

Ah, yes, you do need system.util.sendMessage, but with scope=‘S’. Scope ‘C’ broadcasts to Vision clients.

Transistor · February 21, 2021, 1:32pm

Thanks, guys. No success yet. When I run the following code the first two messages return the expected values but msg is empty.

	msg = system.perspective.sendMessage(
		project = system.project.getProjectName(),
		messageHandler = 'configUpdate', 
		payload = {'table': 'config'}, 
		scope = "S"
	)
	system.perspective.print(system.project.getProjectName())
	system.perspective.print('sendMessage configUpdate')
	system.perspective.print(msg)

pturmel · February 21, 2021, 1:34pm

See edited emphasis above.

Transistor · February 21, 2021, 1:47pm

Thanks, Phil. (I'm blaming you for that one from earlier. )

Now I'm getting a response to my sendMessage:

[type=Session,sessionId=5a8074b9-acde-4b50-b52f-c17380322f84,
project=MyProject,
messageHandler=configUpdate,
filterParams={userRoles=, scope=S, userZones=},
isRequest=no,
sendStatus=SENT,
type=Session,
sessionId=dbf2304c-01bf-4ffa-b3fd-5aba862d7341,
project=MyProject,
messageHandler=configUpdate,
filterParams={userRoles=, scope=S, userZones=},
isRequest=no,
sendStatus=SENT]

so it looks like it's seeing another client. The clients still aren't triggering. (I just have a system.perspective.print in the onMessageReceived for now. Listen Scopes is set to Session.)

Transistor · February 21, 2021, 2:53pm

Reading through the documentation again, I'm beginning to think that component message handlers can't see system.util.sendMessage messages but only system.perspective.sendMessage messages. Component message handlers says:

The idea being that some other component will broadcast a message, and if the type of the message matches what the Message Handler is listening for, the Message Handler will execute a script.

That means I am going about this the wrong way and that I need to:

Create a Project Browser | Session Events | Message | configUpdate session message handler to receive a broadcast message.
Have that create a system.perspective.sendMessage and pass the payload to the components in the session.

I can't get the session message handler to detect the incoming message though.

Am I on the right track?

bmusson · February 21, 2021, 8:07pm

It's a little bit simpler than that.
system.perspective.sendMessage() takes a sessionID parameter that you can use to directly send messages to other sessions.

Try something like this:

def broadcastPerspectiveMessage(messageType, payload):
	"""Broadcast a Perspective message to all sessions in the current project."""
	project = system.util.getProjectName()
	sessions = system.perspective.getSessionInfo(projectFilter=project)	
	scope = 'session'
	for session in sessions:
		try:
			system.perspective.sendMessage(messageType, payload, scope=scope, sessionID=session['id'])
		except:
			# Try/except to avoid 'Unvalid UUID String' errors from open designer sessions.
			pass

Then on your save button:

payload = {
	'sessionID': self.session.props.id
}
shared.util.broadcastPerspectiveMessage("ConfigTableSaved", payload)

And on a message handler on your table (with message type of ConfigTableSaved listening to Session messages):

if payload['sessionID'] == self.session.props.id:
	# Do something on the session that initiated the save.
	pass
else:
	# Do something on all other listening sessions.
	pass
		
# Do something for all sessions.
pass

Transistor · February 21, 2021, 8:59pm

Thanks for this information. I haven’t found anything like this. All the documentation and examples suggest that I can just send a broadcast using system.util.sendMessage and the others will pick it up. Your approach seems to target them all individually.

Q1. Where does the broadcastPerspectiveMessage code go? Scriptiong | Project Library or on the gateway?
Q2. You seem to be bypassing the Session Event message handler and going directly to the component message handler. Can you do that?