@Yveaux For your influx flow you can try this :
[{"id":"8347dab9.7cb828","type":"mqtt-broker","broker":"localhost","port":"1883","clientid":""},{"id":"d92d398d.26d2c8","type":"mqtt in","name":"Temperature Bureau","topic":"MySensors/4/1","broker":"8347dab9.7cb828","x":159,"y":103,"z":"183ecd0f.e7c133","wires":[["a929fd06.56d6"]]},{"id":"a929fd06.56d6","type":"function","name":"","func":"var newMsg={};\nnewMsg.payload = new Buffer(\"temp,location=Bureau value=\"+msg.payload,\"binary\");\nreturn newMsg;","outputs":1,"noerr":0,"x":354,"y":103,"z":"183ecd0f.e7c133","wires":[["4b2e850f.b4d17c"]]},{"id":"4b2e850f.b4d17c","type":"http request","name":"","method":"POST","ret":"bin","url":"http://localhost:8086/write?db=test","x":505,"y":103,"z":"183ecd0f.e7c133","wires":[[]]}]