UM 8.3: Event Streams

[Susan_Shamgar]

We want to make sure all IA documentation is clear, complete, and helpful for all users. If you noticed anything confusing or missing, this is the perfect place to let us know how we can improve!

This forum topic is where you can provide the docs team with feedback on the Event Streams page. To report issues on a different piece of documentation, or for more general docs feedback, please email us at docs@inductiveautomation.com.

[Sfenwick]

Passing some feedback I found

Event Streams Thoughts and Questions

I really like the idea of the event streams module. Just barely cobbled together a tag event stream from a UDT instance a log in a data base (much like a transaction group but cleaner IMO). I have so much more to learn with this new feature. I wanted to see who else out there is playing with event streams. What are you building /thinking of building with it? Next I’m gonna try out a “tags to Kafka” stream for certain UDTs as a way of logging domain events. I really like this compared to MQTT’s…

[jomaldonado209]

I was a bit confused by this table here in the encoder section.
I don't really know what its for, if I'm supposed to interact with it or its supposed to show me something.

I've only played with JSON encoding so far but I don't see it doing anything.

Didn't cause an issue though, my stream still worked.

I was kind of hoping it would maybe preview the encoded message for me or something. Just not sure what its for though.

[Brandon_Au]

Hey, sorry for the delay! So encoding your data to a specific format will make it compatible with the type of handler(s) you are using. That's why there's also an encoding stage after the transform stage: the format might be different after transforming, so encoding it again will set it back to whichever format you want.

As far as the table goes, if you change the encoding format to String, it should populate that table with an additional row. That new row will let you change the encoding property from UTF-8 to something else, like UTF-16.

Currently, that table will populate with that new row even if the encoding format is changed to ByteArray or back to JSON, but that's a bug. I believe development also has a ticket open to update the UI so that it uses something other than a table to make it less misleading. I'll update the docs to explain the encoder property.

[Brandon_Tanner]

Can you provide more clarification on the syntax for the expression used in the value field of the tag message handler? I would like to use a value from the payload; however, the handler expression language that works in the filter portion is giving me an “ExpressionException: unable to parse ‘value’ field.” error.

Additionally, it would be helpful to be able to see what the contents of the data and metadata payloads are.

[Brandon_Au]

Hey Brandon, what syntax are you using for the expression? I got the same error as you when using event.data.value, but it started working after encapsulating the expression in curly brackets ({event.data.value}).

As for your second part, do you mean it would be nice to see the different types of data and metadata you can reference? That information should be on that linked Source Data and Metadata page in the table. If you’re talking about seeing the actual payload values, you can try writing a script in the filter stage to print the contents to your log files. If you want something a little more fine-tuned and baked into Ignition, I’d recommend submitting feature request to the IA ideas page.