Papertrail not using system host name

Question

I am trying to figure out why Papertrail it not using the hostname as is advertised on this documentation page:

Papertrail honors the hostname sent by your log sender, such as rsyslog or remote_syslog2. By default, this is the system hostname.

Using this docker compose snippet:

services:
  nginx:
    logging:
      driver: syslog
      options:
        syslog-address: udp://logsN.papertrailapp.com:XXXXX
        tag: nginx

creates log entries on Papertrail with the machine IP instead of the hostname.

I have tested the same configuration using local syslog, with the below docker-compose snippet, and I could see the hostname in the log properly.

services:
  nginx:
    logging:
      driver: syslog

Not sure what I am missing.

Answer 1

With the help of the guys at Papertrail, here is the answer:

By default, Docker's syslog driver assumes the logs are being sent to a local syslog daemon, which means the hostname is omitted. To tell it otherwise, specify syslog-format: rfc5424.

logging:
  driver: syslog
  options:
    syslog-format: rfc5424
    syslog-address: udp://logsN.papertrailapp.com:XXXXX
    tag: nginx