Tradfri but not carefree.
the good news first, it is still green, online after 2 days 
However, I see quite a few exceptions in the log, they seem to originate from a recurrent task scheduled for every minute. This task does not fail every minute, all ran fine for 10 hours and then exception on 13:00:19.260,13:01:19.340, 13:02:19.258 ,
… 13:08:19.272. Then all is fine for a while and then it fails again at the 19th second
2019-05-02 13:00:19.260 [ERROR] [alifornium.core.network.CoapEndpoint] - Exception in protocol stage thread: This is not a JSON Array.
java.lang.IllegalStateException: This is not a JSON Array.
at com.google.gson.JsonElement.getAsJsonArray(JsonElement.java:106) ~[?:?]
at org.eclipse.smarthome.binding.tradfri.handler.TradfriGatewayHandler.onUpdate(TradfriGatewayHandler.java:304) ~[?:?]
at org.eclipse.smarthome.binding.tradfri.internal.TradfriCoapHandler.onLoad(TradfriCoapHandler.java:65) ~[?:?]
at org.eclipse.californium.core.CoapClient$MessageObserverImpl.deliver(CoapClient.java:1016) ~[249:californium-osgi:1.0.6]
at org.eclipse.californium.core.CoapClient$MessageObserverImpl.succeeded(CoapClient.java:995) ~[249:californium-osgi:1.0.6]
at org.eclipse.californium.core.CoapClient$MessageObserverImpl.onResponse(CoapClient.java:974) ~[249:californium-osgi:1.0.6]
at org.eclipse.californium.core.coap.Request.setResponse(Request.java:509) ~[249:californium-osgi:1.0.6]
at org.eclipse.californium.core.network.EndpointManager$ClientMessageDeliverer.deliverResponse(EndpointManager.java:267) ~[249:californium-osgi:1.0.6]
at org.eclipse.californium.core.network.stack.CoapStack$StackTopAdapter.receiveResponse(CoapStack.java:193) ~[249:californium-osgi:1.0.6]
at org.eclipse.californium.core.network.stack.AbstractLayer.receiveResponse(AbstractLayer.java:98) ~[249:californium-osgi:1.0.6]
at org.eclipse.californium.core.network.stack.ObserveLayer.receiveResponse(ObserveLayer.java:137) ~[249:californium-osgi:1.0.6]
at org.eclipse.californium.core.network.stack.AbstractLayer.receiveResponse(AbstractLayer.java:98) ~[249:californium-osgi:1.0.6]
at org.eclipse.californium.core.network.stack.BlockwiseLayer.receiveResponse(BlockwiseLayer.java:321) ~[249:californium-osgi:1.0.6]
at org.eclipse.californium.core.network.stack.AbstractLayer.receiveResponse(AbstractLayer.java:98) ~[249:californium-osgi:1.0.6]
at org.eclipse.californium.core.network.stack.ReliabilityLayer.receiveResponse(ReliabilityLayer.java:269) ~[249:californium-osgi:1.0.6]
at org.eclipse.californium.core.network.stack.AbstractLayer.receiveResponse(AbstractLayer.java:98) ~[249:californium-osgi:1.0.6]
at org.eclipse.californium.core.network.stack.CoapStack.receiveResponse(CoapStack.java:135) ~[249:californium-osgi:1.0.6]
at org.eclipse.californium.core.network.CoapEndpoint$InboxImpl.receiveMessage(CoapEndpoint.java:656) ~[249:californium-osgi:1.0.6]
at org.eclipse.californium.core.network.CoapEndpoint$InboxImpl.access$700(CoapEndpoint.java:562) ~[249:californium-osgi:1.0.6]
at org.eclipse.californium.core.network.CoapEndpoint$InboxImpl$1.run(CoapEndpoint.java:574) ~[249:californium-osgi:1.0.6]
at org.eclipse.californium.core.network.CoapEndpoint$5.run(CoapEndpoint.java:721) [249:californium-osgi:1.0.6]
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) [?:?]
at java.util.concurrent.FutureTask.run(FutureTask.java:266) [?:?]
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(ScheduledThreadPoolExecutor.java:180) [?:?]
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:293) [?:?]
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) [?:?]
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) [?:?]
at java.lang.Thread.run(Thread.java:748) [?:?]
I searched the archives and found it mentioned once before in 2017
Things still seem to work. it just trashes the logs and openhab2 lags when it’s busy throwing exceptions.