OH 3.2/Influx DB: Do not persist every change for dedicated items

Dear all,
I do have an item that fetches an update every second or less.
To not overload the persistence service InfluxDB, I would like to persist the change only every 5 seconds.

Currently my strategy is:
Items {
* : strategy = everyChange

How can I change the strategy for only a single item e.g. to persist the change every 5 minutes.

Thanks for your feedback.


create a group gEvery5Seconds, put the items you need in it or define the special item.

Strategies {
    every5Seconds : "*/5 * * * * ?"
    everyMinute : "0 * * * * ?"
    default = everyMinute

gEvery5Seconds* : strategy = every5Seconds
itemEvery5Seconds : strategy = every5Seconds

Not tested. :wink:

Hope, this helps.

Just to elaborate a bit on @HFM’s answer. The * under Items will apply to every Item. So your .persist file will need two entries, one which has the everyChange applied to every Item except this one Item and another one that has the every5Seconds strategy. To accomplish this the easiest way is to use Groups.

Thanks for your response.

The issue is exactly with

How do I specify that “all items expect ITEM_XYZ applies everyChange” ?

Thanks. Best

You can’t. You have to list all the Items but the one for one strategy and just the one Item for the other strategy. You have a bit more control and it’s a little easier if you use Groups. then you can use MyGroup* for the one strategy and all members of that Group will be persisted based on that strategy.

There is no shortcut.

@ruebox Here is a little helper JS script:

var runtime = (typeof(require) === "function") ? require("@runtime") : {
  itemRegistry: itemRegistry,
  events: events,
  items: items,
  DateTimeType: DateTimeType

// filter Items by Type
var filteredItems = utils.javaSetToJsArray(runtime.itemRegistry.getItems().stream().filter((i) => { return i.type.indexOf("Rollershutter") >= 0; }));  
console.log("FilterdItems Length " + filteredItems.length);

for (var i = 0; i < filteredItems.length; i++) {
  console.log("Item " + i );
  console.log("Itemname " + filteredItems1[i].name);
  console.log("ItemType " + filteredItems1[i].type);
  console.log("ItemState " + filteredItems1[i].state);
  console.log("ItemGroups" + filteredItems1[i].groupNames);
  var tempItem = items.getItem(filteredItems1[i].name);
  // add Group

This example looks for all Rollershutter items and adds the group “gDatabaseRollershutter”. In my scenario I used it to put all Rollershutter items into a group, so that I can index them in a database.

  • Create a new Script or Rule
  • edit the types or adjust the filter expression to your needs
  • edit the “addGroups” line with your groups

if you need help, let me know

All these answers are all good, but is it really a problem to be writing to influxdb every second? Are you hitting any kind of performance issues as a consequence? If not, it will be a lot easier to simply leave it as-is.

Influxdb (on dedicated hardware) supports hundreds of thousands of writes per second.

To be honest, I do not know. I have 20 sensors with approximately 100 items which write on everyChange. So there is a lot of traffic, but I think it is a lot more than 1 second on average.

I would try and monitor load of the host.

Have a great Easter Monday!

My approach has been to only store metrics for the things that I actually care about measuring by using a specific group. But then again, I’m generating the openhab configuration so it’s very easy to have various types of items automatically added to that group.

With influxdb you can enable a special “_internal” database that gives you metrics on influxdb itself. I haven’t tried it, but it but it might give you more data.

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