Telegraf getting 400 errors

Telegraf
,
1

Is this only used for client authentification? Or is this always required to connect to influxdb via https?
According to Telegraf TLS Client Authentication in Influxdb output - #3 by cruscio they are not necessary for TLS usage without client auth.

[[output.influxdb]]
urls = ["https://influx.some.where:8086"]
# --- SNIP. --- 
  ## Optional TLS Config for use on HTTP connections.
#tls_ca = "/etc/telegraf/ca.pem"
#tls_cert = "/etc/telegraf/cert.pem"
#tls_key = "/etc/telegraf/key.pem"
  ## Use TLS but skip chain & host verification
#insecure_skip_verify = false

I seem to be unable to find appropriate documentation.

2

Backgroud:

I set up a TLS reverse Proxy which works fine for a lot of other services but for influx I keep getting the following:

2018-10-27T15:06:00Z E! [outputs.influxdb] when writing to [https://influx.some.where:8086]: 400 Bad Request
2018-10-27T15:06:00Z E! Error writing to output [influxdb]: could not write any address

Configuration posted here: TLS configuration with telefgraf and influxdb behind nginx proxy TLS Termination endpoint - #2 by drahnr