Kamailio limit CPS/CPM/Concurrent calls per gateway.

Small task to make some generic limiters for calls per gateway, which in my case - destination.
Limiting concurrent calls is based on dialog module, limiting CPS/CPM - on htable module, actual solution taken from here.

On a modparam I'm pointing only on settings, that needed for this solution, so, if you want to adopt it to your case - use your settings along with provided.

loadmodule "htable.so"
...
modparam("htable", "htable", "rhs=>size=32;initval=0;autoexpire=300;")
modparam("htable", "htable", "rhm=>size=32;initval=0;autoexpire=1800;")

loadmodule "dialog.so"
...
modparam("dialog", "profiles_with_value", "concurrent_calls")

...

request_route {

...

   if (is_method("INVITE")) {

      route(LIMIT_CALLS)

   }

...

}

route[LIMIT_CALLS] {
    # Limit oncurrent calls per gateway
    if (!dlg_isflagset("1")) {
        if (get_profile_size("concurrent_calls", "$td", "$avp(calls)")) {
            $avp(concCallLimit) = <ACTUAL_CONCURRENT_CALLS_LIMIT_HERE>;
            if ($avp(calls) >= $avp(concCallLimit)) {
                xlog("L_INFO", "Concurrent calls to $td limit reached");
                send_reply("503", "Calls limit reached");
                exit;
            } else {
                dlg_manage();
                dlg_setflag("1");
                set_dlg_profile("concurrent_calls","$td");
            }
        }
    }

    $avp(rateHashSec) = "$td:sec:"+$timef(%Y/%m/%d_%H_%M_%S);
    $avp(rateHashMin) = "$td:min:"+$timef(%Y/%m/%d_%H_%M_00);

    $avp(ratePerSec) = $shtinc(rhs=>$avp(rateHashSec));
    $avp(ratePerMin) = $shtinc(rhm=>$avp(rateHashMin));
    $avp(limitPerSec) = <ACTUAL_LIMIT_PER_SECOND_HERE>;
    $avp(limitPerMin) = <ACTUAL_LIMIT_PER_MINUTE_HERE>;
    if ($avp(ratePerSec) > $avp(limitPerSec) || $avp(ratePerMin) > $avp(limitPerMin)) {
        xlog("L_INFO", "CPS/CPM Limit on $td");
        send_reply("503", "CPS/CPM Limit on $td");
        exit;
    }
}

Main idea in concurrent calls - use dialog profiles and ability to count them. Point, it can be used only in stateful mode, so dialogs are tracked and deleted after it's end. Flag "1" is used not to count same dialog several times.

Idea in CPS/CPM limiter - using htable with keys, that can be accessible only in specific time due name formation rules.

And $td is used to limit to current destination, that was set up previously (no touching this part)
This one is not very best for copy-paste, so, adopt it to your needs :)