Use Own Systemd Unit File

I would like to use my own systemd unit file for logstash because I am starting a dedicated logstash process for each configfile via initscript.

I noticed that the logstash unit file is generated via /usr/share/logstash/bin/system-install. Not only during installation, it seems that this happens regulary. How can I disable this "feature" so i can use my own systemd unit file for logstash?

Ok I found the reason why the file has been overwritten regulary. This has been done by the logstash puppet module, I've changed the corresponding lines:

# Invoke 'system-install', which generates startup scripts based on the
# contents of the 'startup.options' file.
# Only if restart_on_change is not false
if $::logstash::restart_on_change {
  exec { 'logstash-system-install':
   #command     => "${logstash::home_dir}/bin/system-install",
    command     => "/bin/true",
    refreshonly => true,
    notify      => Service['logstash'],
  }
} else {
  exec { 'logstash-system-install':
   #command     => "${logstash::home_dir}/bin/system-install",
    command     => "/bin/true",
    refreshonly => true,
  }
}