Script Library reloading and Project Inheritance

Ignition
1

I’m playing around with multi-project inheritance trees, for example where two runnable projects inherit from a single “Global” project, to see how project saves impact inherited script libraries, and i’m seeing odd results that I can’t explain.

I set something dumb up just for testing… I know you shouldn’t perform tag reads/writes within the root of a script library. However…

I have this script library defined in my Global project (which is not overridden in either of the two inheriting Main projects):

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tagPath = '[default]Testing/Test 2'
oldVal = system.tag.readBlocking(tagPath)[0].value
r = system.tag.writeBlocking(tagPath, oldVal + 1)
system.util.getLogger('BOB').info('{} -> {}'.format(oldVal, r))

Every time the library reloads it should increment the Test 2 tag value by 1.

  • If I save the Global project, it increments 1 (I kind of expected it to flakily increment 1 or 2 depending on the speed that each Main project reloads the script library…)
  • If I save the “Main” project, it increments 1. Edit: If I set the GSP to the Global project, it doesn’t increment at all.
  • If I save the “Main2” project, it doesn’t increment at all.

I’m just looking to understand what’s happening here. I would have expected saving Main2 would also increment the tag value by 1, but it’s not. And why does saving Global not write 1 or sometimes 2?

Projects defined:

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Edit:

Note: the Main project is the global scripting project (GSP).

It seems to have to do with the GSP, but I would have expected a change to an inherited script library would reload it in all inherting projects which would then run it and therefore write to the tag in all locations. I added a lock to get rid of the race condition where two threads could read the current tag value at the same time and hence increment by 1 always instead of 2:

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2

First - is this 8.1 or 8.3?

Second - don't use tags as your counter object - too race-y. Just store an int in globals if you want an accurate count.

3

It’s 8.3. I tried using a global variable as well but had the same “issue”, but in that case it’s due to different scopes I think… it depends where you read the value of the global key from as to what value you’ll see.

4

Do keep in mind that each leaf project, and the GSP if not a leaf itself, will all have their own interpreters. Only system.util.globals is shared across the JVM.

5

Would this not fix the raceyness with tags?

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6

Yes, until some other programmer stomps on your too-common name. (One of the reasons system.util.globalVarMap() takes a namespace argument.)

7

Of course, but I point you back to here :stuck_out_tongue:

8

Good thing you made it a screenshot, so desperate future visitors cannot copy/paste it... :frowning:

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