sendMessage causing script to stop execution

Ignition
1

I am having an issue where system.perspective.sendMessage seems to stop execution of a change script.

def valueChanged(self, previousValue, currentValue, origin, missedEvents):
	from time import sleep 
	
	def confirm_reset():
		sleep(5)
		if self.custom.timingActive or self.custom.interruptFlag:
			self.custom.timingActive = False
			system.perspective.sendMessage('changeMessage', payload={'text': 'script', 'instanceId': self.view.custom.instanceId}, scope='page')
			self.custom.interruptFlag = True
			
	if currentValue.value:
		system.util.invokeAsynchronous(confirm_reset, [], "Confirm Delay")

I have split the 2 properties interruptFlag and timingActive to help me see what was going on. As posted, interruptFlag does not get set. As soon as I comment out the system.perspective.sendMessage, interruptFlag will be set as expected. I have been over and over this code to see what I may have fat fingered and can't find anything.

Any help would be greatly appreaciated.

2

Unless your version of Ignition is really recent, system.util.invokeAsynchronous() does not inherit the Perspective environment needed by system.perspective.sendMessage(). So that call will fail.

3

Running 8.1.44

4

I don't recall what version has that enhancement, and it is not showing in the v8.1 changelogs. I recall @PGriffith making a comment that it was added.

You have self in your closure, so you should be able to extract explicit session and page information from that to use in system.perspective.sendMessage().

5

I tried sending the sessionID to it but it still didn't work. As a workaround, I've moved the sendMessage outside of the called function and leveraged the second call of the change script (false transition) to send the message.

6

When using page scope for your message, you must supply both session and page IDs.

2 Likes
7

I thought I had made that change too, but git blame suggests not. I think I intended to, but wasn't able to with the fragile ScriptContext API in 8.1 (the change has been made to inherit ScriptContext in 8.3).

However, Perspective's session info is in a dedicated ThreadLocal and therefore not part of ScriptContext anyways, so it's a moot point.

2 Likes