Provide an example of using an in-process queue

Author: DarkArc

docs/howto/patterns.rst

@@ -87,6 +87,32 @@ terminates, after canceling the other task::
         for task in pending:
             task.cancel()
 
+In-process queue
+----------------
+
+For simple applications that need to be able to consume and act on multiple
+messages at one, an in-process queue can be leveraged::
+
+    MAX_WORKERS = os.cpu_count()
+
+    queue = asyncio.Queue(MAX_WORKERS)
+
+    async def consumer_handler(websocket):
+        async for message in websocket:
+            await queue.put(message)
+
+    async def worker(websocket):
+        while True:
+            message = await queue.get()
+            result = await long_running_task(message)
+            await websocket.send(result)
+
+    async def handler(websocket):
+        async with asyncio.TaskGroup() as tg:
+            tg.create_task(consumer_handler(websocket))
+            for _ in range(MAX_WORKERS):
+                tg.create_task(worker(websocket))
+
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