System.tag.exists ..... but it doesn't

Ignition
1

If I run the following in the script console

gnamePath = '[MQTT Engine]DCNET/MAP/S1/R1/B1/G10/Name'
if system.tag.exists (gnamePath):
	print 'Tag Exists'

and a folder for [MQTT Engine]DCNET/MAP/S1/R1/B1/G10/ is present , BUT the tag “Name” is NOT present in that folder then this will print " Tag Exists"

The function description is
Checks whether or not a Tag with a given path exists.

The folder has no tags in it is this the problem?

2

What version of Ignition is this happening on?

3

8.1.7

4

Updated to 8.1.12 now getting this message

image

only file in this path is modules file. Tried uninstalling, and downloading designer for reinstall. No luck

5

Delete the 11.0.11.1 folder in that path and you should be able to launch.

6

That fixed the designer launch after upgrade .

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Still have issue with system.tag.exists

7

Have you tried refreshing the tag provider to make sure the folder is actually empty? I just ran a test in 8.1.9 and it worked as expected for me (empty folder and returned false when I checked for a non-existent tag in the empty folder).

Edit: Just wanted to note that the provider I tested against does not use MQTT.

8

Yes. Did this in the tag browser same results.

9

I think this might be a bug that is specific to the MQTT modules.

I thought maybe it affected any ManagedTagProvider implementation but I just tested against the provider from the SDK example and it works as expected.

I’d contact Cirrus Link or maybe paging @wes0johnson will work :slight_smile:

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10

This is not something I’ve seen before. I’m not sure how the MQTT Engine module could be causing this other than maybe with the way we configure the ManagedTagProvider. I believe some of the config options we use are different from the SDK example. I’ll take a look and see if I can repro this and isolate the cause.

11

system.tag.exists expects QualityCode Bad_NotFound to be returned after trying to read a tag that doesn’t exist.

12

Is this not something that is handled by the ManagedTagProvider itself? I just glanced at the SDK example and it doesn’t do anything explicitly around this that I can see…

13

Well, that’s what I thought, but like I said when I tested the MTP example it all works fine :confused:

I’m not sure why it’s not behaving the same for tags from the MQTT provider.

14

I’ll do some digging on my side and see what I can find.

15

So I think I figured this out. I was not able to reproduce with the SDK example, but I was with Engine. This is how I got it to happen:

  1. I created an Edge Node with 3 tags under a single device and published from Transmission
  2. I deleted one of the tags from the Edge side
  3. I restarted MQTT Engine (this is key)
  4. I published a new birth from the Edge

This produced the following:

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The reason is that MQTT Engine does not persist tags. But, it does still persist the tag configuration. So, I think ‘tagExists’ looks to see if it is in the DB tag table - which does not necessarily mean it is visible in Designer. With this, I suspect the tag you are trying to look up did exist at one point and was never deleted from the Ignition Tag DB (via a delete event or similar). But, Engine has since been restarted which is why it is not visible in Designer.

I believe that if you delete that tag from the DB, tagExists will properly return false.