--- a/mod_firewall/definitions.lib.lua	Fri Mar 18 09:45:02 2016 +0000
+++ b/mod_firewall/definitions.lib.lua	Fri Mar 18 09:47:52 2016 +0000
@@ -6,6 +6,9 @@
 
 local set = require"util.set";
 local new_throttle = require "util.throttle".create;
+local new_cache = require "util.cache".new;
+
+local multirate_cache_size = module:get_option_number("firewall_multirate_cache_limit", 1000);
 
 function definition_handlers.ZONE(zone_name, zone_members)
 			local zone_member_list = {};
@@ -15,10 +18,45 @@
 			return set.new(zone_member_list)._items;
 end
 
+-- Helper function used by RATE handler
+local function evict_only_unthrottled(name, throttle)
+	throttle:update();
+	-- Check whether the throttle is at max balance (i.e. totally safe to forget about it)
+	if throttle.balance < throttle.max then
+		-- Not safe to forget
+		return false;
+	end
+end
+
 function definition_handlers.RATE(name, line)
 			local rate = assert(tonumber(line:match("([%d.]+)")), "Unable to parse rate");
 			local burst = tonumber(line:match("%(%s*burst%s+([%d.]+)%s*%)")) or 1;
-			return new_throttle(rate*burst, burst);
+			local max_throttles = tonumber(line:match("%(%s*entries%s+([%d]+)%s*%)")) or multirate_cache_size;
+
+			local cache = new_cache(max_throttles, evict_only_unthrottled);
+
+			return {
+				single = function ()
+					return new_throttle(rate*burst, burst);
+				end;
+				
+				multi = function ()
+					return {
+						poll_on = function (_, key, amount)
+							assert(key, "no key");
+							local throttle = cache:get(key);
+							if not throttle then
+								throttle = new_throttle(rate*burst, burst);
+								if not cache:set(key, throttle) then
+									module:log("warn", "Multirate '%s' has hit its maximum number of active throttles (%d), denying new events", name, max_throttles);
+									return false;
+								end
+							end
+							return throttle:poll(amount);
+						end;
+					}
+				end;
+			};
 end
 
 return definition_handlers;