This is a fluentd parser plugin for parsing the systemd journal export format.

Add this to your fluent.conf

<source>
  @type http
  port 8888
  format journal
</source>

and your boxes can push their journal to the server with

/lib/systemd/systemd-journal-upload -u http://myfluentdserver:8888/journal

A better solution is of course to edit your /etc/systemd/journal-upload.conf to add the proper URL and run the daemon via services. Eg.:

systemctl enable systemd-journal-upload
systemctl start systemd-journal-upload