First: you provide two times

mfoss — Wed, 14 May 2014 11:30:57 +0000

First: you provide two times the out_dir option, which is not allowed: provide only one.
Second: the option is called outdir, not out_dir.
Third: there is a bug in ejabberd that is triggered when the option outdir isn't specified.

So, try with this and it will work:

  mod_muc_log:
    access_admin: muc_admin
    access_create: muc
    access_log: muc
    dirtype: plain
    dirname: room_name
    file_format: html
    outdir: "/srv/http/xmpp-logs/"
    file_permissions:
      mode: 644
      group: 33
    timezone: local

ejabberd - Comments for "mod_muc_log error"

First: you provide two times