I am totally new to InfluxDB but managed to get data into the database, downsample and visualize it.
But I am struggeling with the retention policies.
In my bucket I store different data from different sensors and the default retention is “infinite”. But for one measurement I would like to implement a retention policy of 3 days. If the data is older than three days it can be deleted.
I think you would (will) need to have a separate bucket (whose retention policy is 3 days) and then send & store your data for that one specific measurement in that bucket.
As someone who is also relatively new to InfluxDB, I have found that planning is everything. Buckets (incl. retention times), measurement names, tag names, field names, etc. should all be sketched out before you send your data. I will usually send data to a bucket called JuckBucket which I can make sure is exactly the way it should be before I start sending it to a an actual bucket.
Also, since you mentioned sensor data, if you were grabbing, for example, the current draw (amps) and speed (Hz) from a motor, then you can grab them both at the same time and send them to Influx with the same timestamp. I do this also with temperatures (actual and setpoint), pressure, etc.