Run apt get update in a more reasonable fashion

update.pp

class apt::update {
    # execute apt-get update if any of the following conditions met:
    # - there is no apt-get update cache data (eg. first run)
    # - any file in the /etc/apt/** was changed after the last execution
    # - it was executed more than 24h ago
    $apt_update_min_age_in_seconds = "24 * 60 * 60" # you can edit this

    $apt_update_condition_1 = "[[ ! -f /var/cache/apt/pkgcache.bin ]]"
    $apt_update_condition_2 = "find /etc/apt -cnewer /var/cache/apt/pkgcache.bin | grep ."
    $apt_update_condition_3 = "[[ $(( $(date +%s) - $(stat -c %Z /var/cache/apt/pkgcache.bin) )) -gt $(( ${apt_update_min_age_in_seconds} )) ]]"
    $apt_update_run_check = "bash -c '${apt_update_condition_1} || ${apt_update_condition_2} || ${apt_update_condition_3}'"

    exec { "apt-get update": 
        onlyif  => $apt_update_run_check,
    }
}