MemoryStoreQueue

The following code sample demonstrates using MemoryStoreQueue:ReadAsync() and MemoryStoreQueue:RemoveAsync() to reliably read, process, and remove items from a queue. Though this process can be as complicated as necessary, this example simply sets a flag in the corresponding data store item, which guarantees that every item will eventually be processed even if some of the calls encounter errors or the server crashes:

• If MemoryStoreQueue:ReadAsync() fails, no items are retrieved from the queue. An item will be picked up for processing during the next iteration of the loop.
• If MemoryStoreQueue:ReadAsync() succeeds but DataStoreService:UpdateAsync() fails, the item stays invisible until the queue's invisibility timeout expires, causing the item becoming visible again to be returned in a future loop iteration.
• Similarly, if MemoryStoreQueue:RemoveAsync() fails, the item will become visible again in the future and will be processed again.

Depending on where the failure happens, it's possible that an item will be processed more than once. You should account for that like the following code sample, in which the end result is the same even if DataStoreService:UpdateAsync() is invoked multiple times.

local MemoryStoreService = game:GetService("MemoryStoreService")
local DataStoreService = game:GetService("DataStoreService")

local queue = MemoryStoreService:GetQueue("PlayerQueue")
local dataStore = DataStoreService:GetDataStore("PlayerStore")

while true do
	pcall(function()
		-- wait for an item to process
		local items, id = queue:ReadAsync(1, false, 30)

		-- check if an item was retrieved
		if #items > 0 then
			-- mark the item as processed
			dataStore:UpdateAsync(items[0], function(data)
				data = data or {}
				data.processed = 1
				return data
			end)

			-- remove the item from the queue
			queue:RemoveAsync(id)
		end
	end)
end

The following code sample demonstrates using MemoryStoreQueue:ReadAsync() and MemoryStoreQueue:RemoveAsync() to reliably read, process, and remove items from a queue. Though this process can be as complicated as necessary, this example simply sets a flag in the corresponding data store item, which guarantees that every item will eventually be processed even if some of the calls encounter errors or the server crashes:

• If MemoryStoreQueue:ReadAsync() fails, no items are retrieved from the queue. An item will be picked up for processing during the next iteration of the loop.
• If MemoryStoreQueue:ReadAsync() succeeds but DataStoreService:UpdateAsync() fails, the item stays invisible until the queue's invisibility timeout expires, causing the item becoming visible again to be returned in a future loop iteration.
• Similarly, if MemoryStoreQueue:RemoveAsync() fails, the item will become visible again in the future and will be processed again.

Depending on where the failure happens, it's possible that an item will be processed more than once. You should account for that like the following code sample, in which the end result is the same even if DataStoreService:UpdateAsync() is invoked multiple times.

local MemoryStoreService = game:GetService("MemoryStoreService")
local DataStoreService = game:GetService("DataStoreService")

local queue = MemoryStoreService:GetQueue("PlayerQueue")
local dataStore = DataStoreService:GetDataStore("PlayerStore")

while true do
	pcall(function()
		-- wait for an item to process
		local items, id = queue:ReadAsync(1, false, 30)

		-- check if an item was retrieved
		if #items > 0 then
			-- mark the item as processed
			dataStore:UpdateAsync(items[0], function(data)
				data = data or {}
				data.processed = 1
				return data
			end)

			-- remove the item from the queue
			queue:RemoveAsync(id)
		end
	end)
end