Charting a LastUpdate DateTime value

[rlkoshak (Rich Koshak)]

@ralfonat

Has anything changed from this to OH4? Or is there a more recent version (v2+?) of the binding? How are bindings assigned to items?

As of OH 3, Expire is not a binding. It’s a built in function.

And bindings are not ever assigned to Items. Items support metadata (the stuff between { }) in a .items file. That metadata can be used to link an Item to a Channel, or it can be used to configure the Item’s behavior (Autoupdate, Expire) or MainUI (State Description, Default X Widgets), 3rd party service integration (Google Assistant, Alexa integration), and you can put your own stuff into Item metadata.

As for Expire, it follows the same format for the Item metadata as was used in 2.5 to configure the binding. In OH 3 a number of new features were added:

• change whether Expire updates or commands the Item
• option to ignore state updates that do not result in a change
• option to ignore commands

I don’t see it documented anywhere in the docs. It probably should be a section in Items. It’s not been a big deal until now I think because it’s self documenting in the UI.

One thing you can do to learn the text file syntax of a Thing or Item Metadata in a text file is to configure an example in the UI, click on the Code tab, and translate the YAML you find there to the custom XText syntax used in .items or .things files.

For example, for metadata, the overall syntax is (see Items | openHAB):

<namespace>="<value>"[<config1>="<value>", <config2>="<value>", ...]

So given:

the metadata would be

expire="1h2m3s,command=ON"[ignoreStateUpdates="true", ignoreCommands="true"]

The extent to which a Binding is assigned to an Item, it’s done through a Channel Link.

@ralfonat

OK, I understood it more as a architectural decision, as there currently doesn’t seem to be a “device is offline/not reporting” handling neither in logic, nor in persistance nor in charting out of the box. I mean I don’t want to complain, just want to understand that this is currently by design not because of my lack of knowledge/experience.

It’s hard to make something out-of-the-box because what constitutes “offline/not reporting” can vary widely from technology to technology and from device to device.

But there are two rule templates on the marketplace that handle these use cases.

• Threshold Alert and Open Reminder [4.0.0.0;5.9.9.9] which is configured to call another rule when an Item doesn’t change or update after a time. That called rule can take remedial actions, generate an alert, update an Item, etc.

• Thing Status Reporting [4.0.0.0;5.9.9.9] which will call a rule you write when a Thing changes status (e.g. changes to OFFLINE). The called rule can take remedial actions, generate an alert, update an Item, etc.

@ralfonat

If the arduino itself is offline, I assumed that all the items derived from the channel/links would be marked as offline as well, etc.

There is no such thing as an Item being OFFLINE.

@ralfonat

But is there something that helps here in the connection of the thing to the items?

You can set the Item to some value that indicates it’s offline (not UNDEF or NULL as those don’t get saved, or use periodic persistence strategy to repeat the last state every minute in the database. That will make the chart look more like a stair step than saw toothed. Or you can use Grafana which has more features on how to handle this case built in.