Issue Configuring a Tag with Data from WebDev Post

[FNNewGuy]

Hi,

I have been working to try and send tag configurations from one Gateway to another using the WebDev module.

The issue I have comes down to this. When I run a getConfiguration and then a configure directly on a tag it functions as expected.

However, I have a very similar script in a doPost resource and, while the strings appear identical, the Configure fails when run on the string returned from the WebDev resource.

I have tried all the different ways of formulating the response, tried to jsonEncode the string, and a few methods to strip any kind of formatting but have so far been unsuccessful.

Any help would be greatly appreciated!

Thanks

[YF129701]

Check this out:

system.util.jsonEncode(system.tag.getConfiguration()) exceeds maximum recursion depth / why can't we export MQTT Tag Configuration?

This is unexpected but a known issue that we've already got logged. The workaround on the ticket is to cast each of the dictionaries returned in the getConfiguration result to string before passing to system.util.jsonEncode. result = system.tag.getConfiguration(PathToTag) print system.util.jsonEncode(str(result[0])) What are you hoping to achieve in the end? You aren't going to be able to create or modify MQTT tags by importing whatever you manage to export. They are managed by the MQTT modu…

Specifically, this part:

This is unexpected but a known issue that we've already got logged.

The workaround on the ticket is to cast each of the dictionaries returned in the getConfiguration result to string before passing to system.util.jsonEncode.

result = system.tag.getConfiguration(PathToTag)
print system.util.jsonEncode(str(result[0]))

You would do this in your httpPost response before you send the tag configuration

[PGriffith]

Don't use system.net.httpPost, it's liable to do all kinds of mangling of your input data and responses; use system.net.httpClient.

[FNNewGuy]

Thanks for the response, I did find that post and tried to cast it to a string both before the Post and after. It basically just adds " to both ends and the jsonEncode fails with the error that it is "Not a JSON object" unfortunately.

[FNNewGuy]

This is interesting, I think I had happened across this function before and was trying to avoid it as it says the instances are fairly heavy. Luckily there isn't much else going on in this project though, so this might be the right solution. I'll try some of these out and post if I have success.

[PGriffith]

Put a line like this:

client = system.net.httpClient()

Somewhere in your project library. Literally that - don't put it inside a function or anything.

Then you'll get one ^[1] instance of the HTTP client per Ignition scope (gateway, Vision client, designer) you can re-use as many times as needed in your scripts/transforms/etc.

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1. some pedantic exceptions aside ↩︎

[FNNewGuy]

Hi Paul, thanks for pointing me in the right direction. I was able to get that setup and use it to try and get this working.

(I'm a little curious what the differences and use cases are for this vs the WebDev module but I digress)

At the end of the day I still wasn't able to acheive what I was looking for. I'm very much still learning especially when it comes to interacting over the web. I was able to export the tags into a WebDev resource and then configure them from the export file but could not get the getConfiguration > Post > Configure workflow to work.

Not a huge deal since I am able to get the same result, I was just trying to figure out if it could be done different/more efficiently.

Thanks again for the help!

[pturmel]

@FNNewGuy

this vs the WebDev module

Opposite directions. WebDev exposes an API for external users to target. httpClient targets external APIs.

[FNNewGuy]

Ah, that makes sense. the httpClient doesn't create the URL endpoints like the WebDev module does. Thanks Phil