Limit smoke effects, e.g. from concrete cure

Standardize a "fair limiting" mechanism that
limits the items accepted into a queue, and
returns a uniform random sample when flushed.

Pass all cooking/curing smoke effects into fair
limit queue.

Apply fairl limit queue to fire sparks too.

Pliant concrete curing checks still seem to lag
the server somewhat, but at least now they
shouldn't hammer the client with particles and
kill framerate too.

mods/nc_api/util_misc.lua

@@ -41,6 +41,29 @@ function nodecore.mkreg()
 	return f, t
 end
 
+function nodecore.fairlimit(max)
+	local queue = {}
+	local qty = 0
+	local function add(item)
+		qty = qty + 1
+		if qty > max then
+			local id = math_random(1, qty)
+			if id <= max then
+				queue[id] = item
+			end
+		else
+			queue[qty] = item
+		end
+	end
+	local function flush()
+		local batch = queue
+		queue = {}
+		qty = 0
+		return batch
+	end
+	return add, flush
+end
+
 function nodecore.memoize(func)
 	local cachedval
 	local cached

mods/nc_api_craft/fx_smoke.lua

@@ -1,41 +1,50 @@
 -- LUALOCALS < ---------------------------------------------------------
-local math, minetest, nodecore, type
+local ipairs, math, minetest, nodecore, type
-    = math, minetest, nodecore, type
+    = ipairs, math, minetest, nodecore, type
 local math_random
     = math.random
 -- LUALOCALS > ---------------------------------------------------------
 
+local smoke_add, smoke_flush = nodecore.fairlimit(50)
+
 local smoking = {}
 
+nodecore.register_globalstep("smoke queue", function()
+		for _, item in ipairs(smoke_flush()) do
+			local pos, qty, time = item.pos, item.qty, item.time
+			local now = minetest.get_us_time() / 1000000
+			local key = minetest.hash_node_position(pos)
+			local old = smoking[key]
+			if old and now < old.exp then minetest.delete_particlespawner(old.id) end
+			if (not time) or (time <= 0) then
+				smoking[key] = nil
+				return
+			end
+			if type(qty) ~= "number" then qty = 1 end
+			if qty < 1 then
+				if math_random() > qty then return end
+				qty = 1
+			end
+			smoking[key] = {
+				id = minetest.add_particlespawner({
+						texture = "nc_api_craft_smoke.png",
+						collisiondetection = true,
+						amount = (qty or 2) * time,
+						time = time,
+						minpos = {x = pos.x - 0.4, y = pos.y - 0.4, z = pos.z - 0.4},
+						maxpos = {x = pos.x + 0.4, y = pos.y + 0.4, z = pos.z + 0.4},
+						minvel = {x = -0.1, y = 0.3, z = -0.1},
+						maxvel = {x = 0.1, y = 0.7, z = 0.1},
+						minexptime = 1,
+						maxexptime = 5,
+						minsize = 1,
+						maxsize = 3
+					}),
+				exp = now + time
+			}
+		end
+	end)
+
 function nodecore.smokefx(pos, time, qty)
-	local now = minetest.get_us_time() / 1000000
+	return smoke_add({pos = pos, time = time, qty = qty})
-	local key = minetest.hash_node_position(pos)
-	local old = smoking[key]
-	if old and now < old.exp then minetest.delete_particlespawner(old.id) end
-	if (not time) or (time <= 0) then
-		smoking[key] = nil
-		return
-	end
-	if type(qty) ~= "number" then qty = 1 end
-	if qty < 1 then
-		if math_random() > qty then return end
-		qty = 1
-	end
-	smoking[key] = {
-		id = minetest.add_particlespawner({
-				texture = "nc_api_craft_smoke.png",
-				collisiondetection = true,
-				amount = (qty or 2) * time,
-				time = time,
-				minpos = {x = pos.x - 0.4, y = pos.y - 0.4, z = pos.z - 0.4},
-				maxpos = {x = pos.x + 0.4, y = pos.y + 0.4, z = pos.z + 0.4},
-				minvel = {x = -0.1, y = 0.3, z = -0.1},
-				maxvel = {x = 0.1, y = 0.7, z = 0.1},
-				minexptime = 1,
-				maxexptime = 5,
-				minsize = 1,
-				maxsize = 3
-			}),
-		exp = now + time
-	}
 end

mods/nc_fire/abm.lua

@@ -7,13 +7,10 @@ local math_random
 
 local modname = minetest.get_current_modname()
 
-local sparks = {}
+local sparks_add, sparks_flush = nodecore.fairlimit(50)
-local sparkqty = 0
+
-local sparkmax = 50
 nodecore.register_globalstep("fire sparks", function()
-		if sparkqty < 1 then return end
+		for _, pos in ipairs(sparks_flush()) do
-		for i = 1, #sparks do
-			local pos = sparks[i]
 			minetest.after(math_random(), function()
 					minetest.add_particlespawner({
 							amount = math_random(1, 3),
@@ -35,8 +32,6 @@ nodecore.register_globalstep("fire sparks", function()
 						})
 				end)
 		end
-		sparks = {}
-		sparkqty = 0
 	end)
 
 do
@@ -55,16 +50,7 @@ do
 			chance = 1,
 			nodenames = {modname .. ":fire"},
 			action = function(pos)
-				sparkqty = sparkqty + 1
+				sparks_add(pos)
-				if sparkqty > sparkmax then
-					local sparkid = math_random(1, sparkqty)
-					if sparkid <= sparkmax then
-						sparks[sparkid] = pos
-					end
-				else
-					sparks[sparkqty] = pos
-				end
-
 				local found = {}
 				for _, dp in ipairs(flamedirs) do
 					local npos = vector.add(pos, dp)