Problems with OH2 and mqtt-persistence

Add-ons Bindings
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1

Hi all,

I’m facing some problems trying to get mqtt persistence running with OH2 (online snapshot a day old). Here is my config:

mqtt.cfg
broker.url=tcp://medienkiste:1883
broker.clientId=openhab

mqtt-persistence.cfg
topic=openhab/
message=%1$s, %3$s

I have mosquitto running on a Synology Diskstation (medienkiste). Using e.g. MQTT.fx, I can subscribe to the topic “openhab/” and see state changes of all items being reported. So far so good…

But in habmin, when trying to have a look at persisted data, all i get is an error msg: “error getting list of items supported by the persistence service”. And indeed, looking up persisted items in REST API, i get “Persistence service not queryable: null”. MQTT is set as default persistence service in habmin.

Any helpful thought is highly appreciated!

Cheers,
wickedP

2

I assume that you installed MQTT persistence. Have you created a persistence file? I use MQTT, but log data to standard rrd4j and also to mysql. your mqtt.persist should contain something like:

// persistence strategies have a name and a definition and are referred to in the “Items” section
Strategies {

everyMinute : "0 * * * * ?"

}

Items {

*: strategy = everyMinute, restoreOnStartup

}

3

Yep, my mqtt.persist looks like this:

Strategies {
        everyMinute : "0 * * * * ?"
        default = everyChange
}

Items {
        // persist all items every minute and on every change
        * : strategy = everyChange, everyMinute
}

For testing I set it to everyMinute and this seems to work, since I can subscribe to an mqtt topic and see updates every minute. Only problem is getting access to the mosquitto-db to plot some persistence data. I chose to persist using mqtt becausse it seemed like an easy way to store data externally (my pi got entirely frozen once because the rrd4j-db became too big and i wasn’t able to restrict its size).

4

From the source code of the MQTT persistence service:

It can be used to persist item states through MQTT messages. The service only supports sending of data, not receiving.

So openHAB cannot query MQTT-persisted states, only publish them.

5

oops, could have found that myself. thanks for your help! will switch to rrd4j instead.

6

No worries! For future reference, the wiki page “Persistence” should be kept up to date on which persistence services are queryable.