renamed group_size to num_concurrent in _map

docs/source/pages/control.rst

@@ -96,9 +96,9 @@ When you are dealing with a regular :py:class:`TaskPool <asyncio_taskpool.pool.T
 
 .. code-block:: none
 
-   > map mypackage.mymodule.worker ['x','y','z'] -g 3
+   > map mypackage.mymodule.worker ['x','y','z'] -n 3
 
-The :code:`-g` is a shorthand for :code:`--group-size` in this case. In general, all (public) pool methods will have a corresponding command in the control session.
+The :code:`-n` is a shorthand for :code:`--num-concurrent` in this case. In general, all (public) pool methods will have a corresponding command in the control session.
 
 .. note::
 

docs/source/pages/pool.rst

@@ -46,7 +46,7 @@ Let's take a look at an example. Say you have a coroutine function that takes tw
    async def queue_worker_function(in_queue: Queue, out_queue: Queue) -> None:
        while True:
            item = await in_queue.get()
-           ... # Do some work on the item amd arrive at a result.
+           ... # Do some work on the item and arrive at a result.
            await out_queue.put(result)
 
 How would we go about concurrently executing this function, say 5 times? There are (as always) a number of ways to do this with :code:`asyncio`. If we want to use tasks and be clean about it, we can do it like this:
@@ -141,7 +141,7 @@ Or we could use a task pool:
    async def main():
        ...
        pool = TaskPool()
-       await pool.map(another_worker_function, data_iterator, group_size=5)
+       await pool.map(another_worker_function, data_iterator, num_concurrent=5)
        ...
        pool.lock()
        await pool.gather_and_close()
@@ -231,5 +231,6 @@ One method to be aware of is :py:meth:`.flush() <asyncio_taskpool.pool.BaseTaskP
 
 In general, the act of adding tasks to a pool is non-blocking, no matter which particular methods are used. The only notable exception is when a limit on the pool size has been set and there is "not enough room" to add a task. In this case, both :py:meth:`SimpleTaskPool.start() <asyncio_taskpool.pool.SimpleTaskPool.start>` and :py:meth:`TaskPool.apply() <asyncio_taskpool.pool.TaskPool.apply>` will block until the desired number of new tasks found room in the pool (either because other tasks have ended or because the pool size was increased).
 
-:py:meth:`TaskPool.map() <asyncio_taskpool.pool.TaskPool.map>` (and its variants) will **never** block. Since it makes use of "meta-tasks" under the hood, it will always return immediately. However, if the pool was full when it was called, there is **no guarantee** that even a single task has started, when the method returns.
+:py:meth:`TaskPool.map() <asyncio_taskpool.pool.TaskPool.map>` (and its variants) will **never** block. Since it makes use of a "meta-task" under the hood, it will always return immediately. However, if the pool was full when it was called, there is **no guarantee** that even a single task has started, when the method returns.
+:py:meth:`TaskPool.map() <asyncio_taskpool.pool.TaskPool.map>` (and its variants) will **never** block. Since it makes use of a "meta-task" under the hood, it will always return immediately. However, if the pool was full when it was called, there is **no guarantee** that even a single task has started, when the method returns.
 

src/asyncio_taskpool/pool.py

@@ -31,15 +31,13 @@ import logging
 from asyncio.coroutines import iscoroutine, iscoroutinefunction
 from asyncio.exceptions import CancelledError
 from asyncio.locks import Semaphore
-from asyncio.queues import QueueEmpty
 from asyncio.tasks import Task, create_task, gather
 from contextlib import suppress
 from datetime import datetime
 from math import inf
-from typing import Any, Awaitable, Dict, Iterable, Iterator, List, Set, Union
+from typing import Any, Awaitable, Dict, Iterable, List, Set, Union
 
 from . import exceptions
-from .queue_context import Queue
 from .internals.constants import DEFAULT_TASK_GROUP, DATETIME_FORMAT
 from .internals.group_register import TaskGroupRegister
 from .internals.helpers import execute_optional, star_function
@@ -491,8 +489,6 @@ class TaskPool(BaseTaskPool):
     Adding tasks blocks **only if** the pool is full at that moment.
     """
 
-    _QUEUE_END_SENTINEL = object()
-
     def __init__(self, pool_size: int = inf, name: str = None) -> None:
         super().__init__(pool_size=pool_size, name=name)
         # In addition to all the attributes of the base class, we need a dictionary mapping task group names to sets of
@@ -714,34 +710,6 @@ class TaskPool(BaseTaskPool):
         await task
         return group_name
 
-    @classmethod
-    async def _queue_producer(cls, arg_queue: Queue, arg_iter: Iterator[Any], group_name: str) -> None:
-        """
-        Keeps the arguments queue from :meth:`_map` full as long as the iterator has elements.
-
-        Intended to be run as a meta task of a specific group.
-
-        Args:
-            arg_queue: The queue of function arguments to consume for starting a new task.
-            arg_iter: The iterator of function arguments to put into the queue.
-            group_name: Name of the task group associated with this producer.
-        """
-        try:
-            for arg in arg_iter:
-                await arg_queue.put(arg)  # This blocks as long as the queue is full.
-        except CancelledError:
-            # This means that no more tasks are supposed to be created from this `_map()` call;
-            # thus, we can immediately drain the entire queue and forget about the rest of the arguments.
-            log.debug("Cancelled consumption of argument iterable in task group '%s'", group_name)
-            while True:
-                try:
-                    arg_queue.get_nowait()
-                    arg_queue.item_processed()
-                except QueueEmpty:
-                    return
-        finally:
-            await arg_queue.put(cls._QUEUE_END_SENTINEL)
-
     @staticmethod
     def _get_map_end_callback(map_semaphore: Semaphore, actual_end_callback: EndCB) -> EndCB:
         """Returns a wrapped `end_callback` for each :meth:`_queue_consumer` task that releases the `map_semaphore`."""
@@ -750,23 +718,25 @@ class TaskPool(BaseTaskPool):
             await execute_optional(actual_end_callback, args=(task_id,))
         return release_callback
 
-    async def _queue_consumer(self, arg_queue: Queue, group_name: str, func: CoroutineFunc, arg_stars: int = 0,
-                              end_callback: EndCB = None, cancel_callback: CancelCB = None) -> None:
+    async def _arg_consumer(self, group_name: str, num_concurrent: int, func: CoroutineFunc, arg_iter: ArgsT,
+                            arg_stars: int, end_callback: EndCB = None, cancel_callback: CancelCB = None) -> None:
         """
-        Consumes arguments from the queue from :meth:`_map` and keeps a limited number of tasks working on them.
+        Consumes arguments from :meth:`_map` and keeps a limited number of tasks working on them.
 
-        The queue's maximum size is taken as the limiting value of an internal semaphore, which must be acquired before
-        a new task can be started, and which must be released when one of these tasks ends.
+        `num_concurrent` acts as the limiting value of an internal semaphore, which must be acquired before a new task
+        can be started, and which must be released when one of these tasks ends.
 
         Intended to be run as a meta task of a specific group.
 
         Args:
-            arg_queue:
-                The queue of function arguments to consume for starting a new task.
             group_name:
                 Name of the associated task group; passed into :meth:`_start_task`.
+            num_concurrent:
+                The maximum number new tasks spawned by this method to run concurrently.
             func:
                 The coroutine function to use for spawning the new tasks within the task pool.
+            arg_iter:
+                The iterable of arguments; each element is to be passed into a `func` call when spawning a new task.
             arg_stars (optional):
                 Whether or not to unpack an element from `arg_queue` using stars; must be 0, 1, or 2.
             end_callback (optional):
@@ -776,31 +746,29 @@ class TaskPool(BaseTaskPool):
                 The callback that was specified to execute after cancellation of the task (and the next one).
                 It is run with the task's ID as its only positional argument.
         """
-        map_semaphore = Semaphore(arg_queue.maxsize)  # value determined by `group_size` in :meth:`_map`
+        map_semaphore = Semaphore(num_concurrent)
         release_cb = self._get_map_end_callback(map_semaphore, actual_end_callback=end_callback)
-        while True:
-            # The following line blocks **only if** the number of running tasks spawned by this method has reached the
-            # specified maximum as determined in :meth:`_map`.
+        for next_arg in arg_iter:
+            # When the number of running tasks spawned by this method reaches the specified maximum,
+            # this next line will block, until one of them ends and releases the semaphore.
             await map_semaphore.acquire()
-            # We await the queue's `get()` coroutine and ensure that its `item_processed()` method is called.
-            async with arg_queue as next_arg:
-                if next_arg is self._QUEUE_END_SENTINEL:
-                    # The :meth:`_queue_producer` either reached the last argument or was cancelled.
-                    return
-                try:
-                    await self._start_task(star_function(func, next_arg, arg_stars=arg_stars), group_name=group_name,
-                                           ignore_lock=True, end_callback=release_cb, cancel_callback=cancel_callback)
-                except CancelledError:
-                    map_semaphore.release()
-                    return
-                except Exception as e:
-                    # This means an exception occurred during task **creation**, meaning no task has been created.
-                    # It does not imply an error within the task itself.
-                    log.exception("%s occurred while trying to create task: %s(%s%s)",
-                                  str(e.__class__.__name__), func.__name__, '*' * arg_stars, str(next_arg))
-                    map_semaphore.release()
+            try:
+                await self._start_task(star_function(func, next_arg, arg_stars=arg_stars), group_name=group_name,
+                                       ignore_lock=True, end_callback=release_cb, cancel_callback=cancel_callback)
+            except CancelledError:
+                # This means that no more tasks are supposed to be created from this `arg_iter`;
+                # thus, we can forget about the rest of the arguments.
+                log.debug("Cancelled consumption of argument iterable in task group '%s'", group_name)
+                map_semaphore.release()
+                return
+            except Exception as e:
+                # This means an exception occurred during task **creation**, meaning no task has been created.
+                # It does not imply an error within the task itself.
+                log.exception("%s occurred while trying to create task: %s(%s%s)",
+                              str(e.__class__.__name__), func.__name__, '*' * arg_stars, str(next_arg))
+                map_semaphore.release()
 
-    async def _map(self, group_name: str, group_size: int, func: CoroutineFunc, arg_iter: ArgsT, arg_stars: int,
+    async def _map(self, group_name: str, num_concurrent: int, func: CoroutineFunc, arg_iter: ArgsT, arg_stars: int,
                    end_callback: EndCB = None, cancel_callback: CancelCB = None) -> None:
         """
         Creates tasks in the pool with arguments from the supplied iterable.
@@ -809,23 +777,21 @@ class TaskPool(BaseTaskPool):
 
         All the new tasks are added to the same task group.
 
-        The `group_size` determines the maximum number of tasks spawned this way that shall be running concurrently at
-        any given moment in time. As soon as one task from this group ends, it triggers the start of a new task
+        `num_concurrent` determines the (maximum) number of tasks spawned this way that shall be running concurrently at
+        any given moment in time. As soon as one task from this method call ends, it triggers the start of a new task
         (assuming there is room in the pool), which consumes the next element from the arguments iterable. If the size
-        of the pool never imposes a limit, this ensures that the number of tasks belonging to this group and running
-        concurrently is always equal to `group_size` (except for when `arg_iter` is exhausted of course).
+        of the pool never imposes a limit, this ensures that the number of tasks spawned and running concurrently is
+        always equal to `num_concurrent` (except for when `arg_iter` is exhausted of course).
 
-        This method sets up an internal arguments queue which is continuously filled while consuming the `arg_iter`.
-        Because this method delegates the spawning of the tasks to two meta tasks (a producer and a consumer of the
-        aforementioned queue), it **never blocks**. However, just because this method returns immediately, this does
-        not mean that any task was started or that any number of tasks will start soon, as this is solely determined by
-        the :attr:`BaseTaskPool.pool_size` and the `group_size`.
+        Because this method delegates the spawning of the tasks to a meta task, it **never blocks**. However, just
+        because this method returns immediately, this does not mean that any task was started or that any number of
+        tasks will start soon, as this is solely determined by the :attr:`BaseTaskPool.pool_size` and `num_concurrent`.
 
         Args:
             group_name:
                 Name of the task group to add the new tasks to. It must be a name that doesn't exist yet.
-            group_size:
-                The maximum number new tasks spawned by this method to run concurrently.
+            num_concurrent:
+                The number new tasks spawned by this method to run concurrently.
             func:
                 The coroutine function to use for spawning the new tasks within the task pool.
             arg_iter:
@@ -840,29 +806,21 @@ class TaskPool(BaseTaskPool):
                 It is run with the task's ID as its only positional argument.
 
         Raises:
-            `ValueError`: `group_size` is less than 1.
+            `ValueError`: `num_concurrent` is less than 1.
             `asyncio_taskpool.exceptions.InvalidGroupName`: A group named `group_name` exists in the pool.
         """
         self._check_start(function=func)
-        if group_size < 1:
-            raise ValueError(f"Group size must be a positive integer.")
+        if num_concurrent < 1:
+            raise ValueError("`num_concurrent` must be a positive integer.")
         if group_name in self._task_groups.keys():
             raise exceptions.InvalidGroupName(f"Group named {group_name} already exists!")
         self._task_groups[group_name] = group_reg = TaskGroupRegister()
         async with group_reg:
-            # Set up internal arguments queue. We limit its maximum size to enable lazy consumption of `arg_iter` by the
-            # `_queue_producer()`; that way an argument
-            # TODO: Perhaps this can be simplified to just one meta-task with no need for a queue.
-            #       The limiting factor honoring the group size is already the semaphore in the queue consumer;
-            #       Try to write this without a producer, instead consuming the `arg_iter` directly.
-            arg_queue = Queue(maxsize=group_size)
             meta_tasks = self._group_meta_tasks_running.setdefault(group_name, set())
-            # Start the producer and consumer meta tasks.
-            meta_tasks.add(create_task(self._queue_producer(arg_queue, iter(arg_iter), group_name)))
-            meta_tasks.add(create_task(self._queue_consumer(arg_queue, group_name, func, arg_stars,
-                                                            end_callback, cancel_callback)))
+            meta_tasks.add(create_task(self._arg_consumer(group_name, num_concurrent, func, arg_iter, arg_stars,
+                                                          end_callback=end_callback, cancel_callback=cancel_callback)))
 
-    async def map(self, func: CoroutineFunc, arg_iter: ArgsT, group_size: int = 1, group_name: str = None,
+    async def map(self, func: CoroutineFunc, arg_iter: ArgsT, num_concurrent: int = 1, group_name: str = None,
                   end_callback: EndCB = None, cancel_callback: CancelCB = None) -> str:
         """
         A task-based equivalent of the `multiprocessing.pool.Pool.map` method.
@@ -872,25 +830,23 @@ class TaskPool(BaseTaskPool):
 
         All the new tasks are added to the same task group.
 
-        The `group_size` determines the maximum number of tasks spawned this way that shall be running concurrently at
-        any given moment in time. As soon as one task from this group ends, it triggers the start of a new task
+        `num_concurrent` determines the (maximum) number of tasks spawned this way that shall be running concurrently at
+        any given moment in time. As soon as one task from this method call ends, it triggers the start of a new task
         (assuming there is room in the pool), which consumes the next element from the arguments iterable. If the size
-        of the pool never imposes a limit, this ensures that the number of tasks belonging to this group and running
-        concurrently is always equal to `group_size` (except for when `arg_iter` is exhausted of course).
+        of the pool never imposes a limit, this ensures that the number of tasks spawned and running concurrently is
+        always equal to `num_concurrent` (except for when `arg_iter` is exhausted of course).
 
-        This method sets up an internal arguments queue which is continuously filled while consuming the `arg_iter`.
-        Because this method delegates the spawning of the tasks to two meta tasks (a producer and a consumer of the
-        aforementioned queue), it **never blocks**. However, just because this method returns immediately, this does
-        not mean that any task was started or that any number of tasks will start soon, as this is solely determined by
-        the :attr:`BaseTaskPool.pool_size` and the `group_size`.
+        Because this method delegates the spawning of the tasks to a meta task, it **never blocks**. However, just
+        because this method returns immediately, this does not mean that any task was started or that any number of
+        tasks will start soon, as this is solely determined by the :attr:`BaseTaskPool.pool_size` and `num_concurrent`.
 
         Args:
             func:
                 The coroutine function to use for spawning the new tasks within the task pool.
             arg_iter:
                 The iterable of arguments; each argument is to be passed into a `func` call when spawning a new task.
-            group_size (optional):
-                The maximum number new tasks spawned by this method to run concurrently. Defaults to 1.
+            num_concurrent (optional):
+                The number new tasks spawned by this method to run concurrently. Defaults to 1.
             group_name (optional):
                 Name of the task group to add the new tasks to. If provided, it must be a name that doesn't exist yet.
             end_callback (optional):
@@ -907,16 +863,16 @@ class TaskPool(BaseTaskPool):
             `PoolIsClosed`: The pool is closed.
             `NotCoroutine`: `func` is not a coroutine function.
             `PoolIsLocked`: The pool is currently locked.
-            `ValueError`: `group_size` is less than 1.
+            `ValueError`: `num_concurrent` is less than 1.
             `InvalidGroupName`: A group named `group_name` exists in the pool.
         """
         if group_name is None:
             group_name = self._generate_group_name('map', func)
-        await self._map(group_name, group_size, func, arg_iter, 0,
+        await self._map(group_name, num_concurrent, func, arg_iter, 0,
                         end_callback=end_callback, cancel_callback=cancel_callback)
         return group_name
 
-    async def starmap(self, func: CoroutineFunc, args_iter: Iterable[ArgsT], group_size: int = 1,
+    async def starmap(self, func: CoroutineFunc, args_iter: Iterable[ArgsT], num_concurrent: int = 1,
                       group_name: str = None, end_callback: EndCB = None, cancel_callback: CancelCB = None) -> str:
         """
         Like :meth:`map` except that the elements of `args_iter` are expected to be iterables themselves to be unpacked
@@ -925,11 +881,11 @@ class TaskPool(BaseTaskPool):
         """
         if group_name is None:
             group_name = self._generate_group_name('starmap', func)
-        await self._map(group_name, group_size, func, args_iter, 1,
+        await self._map(group_name, num_concurrent, func, args_iter, 1,
                         end_callback=end_callback, cancel_callback=cancel_callback)
         return group_name
 
-    async def doublestarmap(self, func: CoroutineFunc, kwargs_iter: Iterable[KwArgsT], group_size: int = 1,
+    async def doublestarmap(self, func: CoroutineFunc, kwargs_iter: Iterable[KwArgsT], num_concurrent: int = 1,
                             group_name: str = None, end_callback: EndCB = None,
                             cancel_callback: CancelCB = None) -> str:
         """
@@ -939,7 +895,7 @@ class TaskPool(BaseTaskPool):
         """
         if group_name is None:
             group_name = self._generate_group_name('doublestarmap', func)
-        await self._map(group_name, group_size, func, kwargs_iter, 2,
+        await self._map(group_name, num_concurrent, func, kwargs_iter, 2,
                         end_callback=end_callback, cancel_callback=cancel_callback)
         return group_name
 

tests/test_pool.py

@@ -20,7 +20,6 @@ Unittests for the `asyncio_taskpool.pool` module.
 
 from asyncio.exceptions import CancelledError
 from asyncio.locks import Semaphore
-from asyncio.queues import QueueEmpty
 from datetime import datetime
 from unittest import IsolatedAsyncioTestCase
 from unittest.mock import PropertyMock, MagicMock, AsyncMock, patch, call
@@ -555,28 +554,6 @@ class TaskPoolTestCase(CommonTestCase):
         check_assertions(generated_name, output)
         mock__generate_group_name.assert_called_once_with('apply', mock_func)
 
-    @patch.object(pool, 'Queue')
-    async def test__queue_producer(self, mock_queue_cls: MagicMock):
-        mock_put = AsyncMock()
-        mock_queue_cls.return_value = mock_queue = MagicMock(put=mock_put)
-        item1, item2, item3 = FOO, 420, 69
-        arg_iter = iter([item1, item2, item3])
-        self.assertIsNone(await self.task_pool._queue_producer(mock_queue, arg_iter, FOO + BAR))
-        mock_put.assert_has_awaits([call(item1), call(item2), call(item3), call(pool.TaskPool._QUEUE_END_SENTINEL)])
-        with self.assertRaises(StopIteration):
-            next(arg_iter)
-
-        mock_put.reset_mock()
-
-        mock_put.side_effect = [CancelledError, None]
-        arg_iter = iter([item1, item2, item3])
-        mock_queue.get_nowait.side_effect = [item2, item3, QueueEmpty]
-        self.assertIsNone(await self.task_pool._queue_producer(mock_queue, arg_iter, FOO + BAR))
-        mock_put.assert_has_awaits([call(item1), call(pool.TaskPool._QUEUE_END_SENTINEL)])
-        mock_queue.get_nowait.assert_has_calls([call(), call(), call()])
-        mock_queue.item_processed.assert_has_calls([call(), call()])
-        self.assertListEqual([item2, item3], list(arg_iter))
-
     @patch.object(pool, 'execute_optional')
     async def test__get_map_end_callback(self, mock_execute_optional: AsyncMock):
         semaphore, mock_end_cb = Semaphore(1), MagicMock()
@@ -592,30 +569,28 @@ class TaskPoolTestCase(CommonTestCase):
     @patch.object(pool, 'Semaphore')
     async def test__queue_consumer(self, mock_semaphore_cls: MagicMock, mock__get_map_end_callback: MagicMock,
                                    mock__start_task: AsyncMock, mock_star_function: MagicMock):
-        mock_semaphore_cls.return_value = semaphore = Semaphore(3)
+        n = 2
+        mock_semaphore_cls.return_value = semaphore = Semaphore(n)
         mock__get_map_end_callback.return_value = map_cb = MagicMock()
         awaitable = 'totally an awaitable'
-        mock_star_function.side_effect = [awaitable, awaitable, Exception()]
+        mock_star_function.side_effect = [awaitable, Exception(), awaitable]
         arg1, arg2, bad = 123456789, 'function argument', None
-        mock_q_maxsize = 3
-        mock_q = MagicMock(__aenter__=AsyncMock(side_effect=[arg1, arg2, bad, pool.TaskPool._QUEUE_END_SENTINEL]),
-                           __aexit__=AsyncMock(), maxsize=mock_q_maxsize)
+        args = [arg1, bad, arg2]
         group_name, mock_func, stars = 'whatever', MagicMock(__name__="mock"), 3
         end_cb, cancel_cb = MagicMock(), MagicMock()
-        self.assertIsNone(await self.task_pool._queue_consumer(mock_q, group_name, mock_func, stars, end_cb, cancel_cb))
-        # We expect the semaphore to be acquired 3 times, then be released once after the exception occurs, then
-        # acquired once more when the `_QUEUE_END_SENTINEL` is reached. Since we initialized it with a value of 3,
-        # at the end of the loop, we expect it be locked.
+        self.assertIsNone(await self.task_pool._arg_consumer(group_name, n, mock_func, args, stars, end_cb, cancel_cb))
+        # We expect the semaphore to be acquired 2 times, then be released once after the exception occurs, then
+        # acquired once more is reached. Since we initialized it with a value of 2, we expect it be locked.
         self.assertTrue(semaphore.locked())
-        mock_semaphore_cls.assert_called_once_with(mock_q_maxsize)
+        mock_semaphore_cls.assert_called_once_with(n)
         mock__get_map_end_callback.assert_called_once_with(semaphore, actual_end_callback=end_cb)
         mock__start_task.assert_has_awaits(2 * [
             call(awaitable, group_name=group_name, ignore_lock=True, end_callback=map_cb, cancel_callback=cancel_cb)
         ])
         mock_star_function.assert_has_calls([
             call(mock_func, arg1, arg_stars=stars),
-            call(mock_func, arg2, arg_stars=stars),
-            call(mock_func, bad, arg_stars=stars)
+            call(mock_func, bad, arg_stars=stars),
+            call(mock_func, arg2, arg_stars=stars)
         ])
 
         mock_semaphore_cls.reset_mock()
@@ -626,61 +601,53 @@ class TaskPoolTestCase(CommonTestCase):
         # With a CancelledError thrown while starting a task:
         mock_semaphore_cls.return_value = semaphore = Semaphore(1)
         mock_star_function.side_effect = CancelledError()
-        mock_q = MagicMock(__aenter__=AsyncMock(return_value=arg1), __aexit__=AsyncMock(), maxsize=mock_q_maxsize)
-        self.assertIsNone(await self.task_pool._queue_consumer(mock_q, group_name, mock_func, stars, end_cb, cancel_cb))
+        self.assertIsNone(await self.task_pool._arg_consumer(group_name, n, mock_func, args, stars, end_cb, cancel_cb))
         self.assertFalse(semaphore.locked())
-        mock_semaphore_cls.assert_called_once_with(mock_q_maxsize)
+        mock_semaphore_cls.assert_called_once_with(n)
         mock__get_map_end_callback.assert_called_once_with(semaphore, actual_end_callback=end_cb)
         mock__start_task.assert_not_called()
         mock_star_function.assert_called_once_with(mock_func, arg1, arg_stars=stars)
 
     @patch.object(pool, 'create_task')
-    @patch.object(pool.TaskPool, '_queue_consumer', new_callable=MagicMock)
-    @patch.object(pool.TaskPool, '_queue_producer', new_callable=MagicMock)
-    @patch.object(pool, 'Queue')
+    @patch.object(pool.TaskPool, '_arg_consumer', new_callable=MagicMock)
     @patch.object(pool, 'TaskGroupRegister')
     @patch.object(pool.BaseTaskPool, '_check_start')
-    async def test__map(self, mock__check_start: MagicMock, mock_reg_cls: MagicMock, mock_queue_cls: MagicMock,
-                        mock__queue_producer: MagicMock, mock__queue_consumer: MagicMock, mock_create_task: MagicMock):
+    async def test__map(self, mock__check_start: MagicMock, mock_reg_cls: MagicMock, mock__arg_consumer: MagicMock,
+                        mock_create_task: MagicMock):
         mock_group_reg = set_up_mock_group_register(mock_reg_cls)
-        mock_queue_cls.return_value = mock_q = MagicMock()
-        mock__queue_producer.return_value = fake_producer = object()
-        mock__queue_consumer.return_value = fake_consumer = object()
-        fake_task1, fake_task2 = object(), object()
-        mock_create_task.side_effect = [fake_task1, fake_task2]
+        mock__arg_consumer.return_value = fake_consumer = object()
+        mock_create_task.return_value = fake_task = object()
 
-        group_name, group_size = 'onetwothree', 0
+        group_name, n = 'onetwothree', 0
         func, arg_iter, stars = AsyncMock(), [55, 66, 77], 3
         end_cb, cancel_cb = MagicMock(), MagicMock()
 
         with self.assertRaises(ValueError):
-            await self.task_pool._map(group_name, group_size, func, arg_iter, stars, end_cb, cancel_cb)
+            await self.task_pool._map(group_name, n, func, arg_iter, stars, end_cb, cancel_cb)
         mock__check_start.assert_called_once_with(function=func)
 
         mock__check_start.reset_mock()
 
-        group_size = 1234
+        n = 1234
         self.task_pool._task_groups = {group_name: MagicMock()}
 
         with self.assertRaises(exceptions.InvalidGroupName):
-            await self.task_pool._map(group_name, group_size, func, arg_iter, stars, end_cb, cancel_cb)
+            await self.task_pool._map(group_name, n, func, arg_iter, stars, end_cb, cancel_cb)
         mock__check_start.assert_called_once_with(function=func)
 
         mock__check_start.reset_mock()
 
         self.task_pool._task_groups.clear()
-        self.task_pool._before_gathering = []
 
-        self.assertIsNone(await self.task_pool._map(group_name, group_size, func, arg_iter, stars, end_cb, cancel_cb))
+        self.assertIsNone(await self.task_pool._map(group_name, n, func, arg_iter, stars, end_cb, cancel_cb))
         mock__check_start.assert_called_once_with(function=func)
         mock_reg_cls.assert_called_once_with()
         self.task_pool._task_groups[group_name] = mock_group_reg
         mock_group_reg.__aenter__.assert_awaited_once_with()
-        mock_queue_cls.assert_called_once_with(maxsize=group_size)
-        mock__queue_producer.assert_called_once()
-        mock__queue_consumer.assert_called_once_with(mock_q, group_name, func, stars, end_cb, cancel_cb)
-        mock_create_task.assert_has_calls([call(fake_producer), call(fake_consumer)])
-        self.assertSetEqual({fake_task1, fake_task2}, self.task_pool._group_meta_tasks_running[group_name])
+        mock__arg_consumer.assert_called_once_with(group_name, n, func, arg_iter, stars,
+                                                   end_callback=end_cb, cancel_callback=cancel_cb)
+        mock_create_task.assert_called_once_with(fake_consumer)
+        self.assertSetEqual({fake_task}, self.task_pool._group_meta_tasks_running[group_name])
         mock_group_reg.__aexit__.assert_awaited_once()
 
     @patch.object(pool.TaskPool, '_map')
@@ -688,18 +655,18 @@ class TaskPoolTestCase(CommonTestCase):
     async def test_map(self, mock__generate_group_name: MagicMock, mock__map: AsyncMock):
         mock__generate_group_name.return_value = generated_name = 'name 1 2 3'
         mock_func = MagicMock()
-        arg_iter, group_size, group_name = (FOO, BAR, 1, 2, 3), 2, FOO + BAR
+        arg_iter, num_concurrent, group_name = (FOO, BAR, 1, 2, 3), 2, FOO + BAR
         end_cb, cancel_cb = MagicMock(), MagicMock()
-        output = await self.task_pool.map(mock_func, arg_iter, group_size, group_name, end_cb, cancel_cb)
+        output = await self.task_pool.map(mock_func, arg_iter, num_concurrent, group_name, end_cb, cancel_cb)
         self.assertEqual(group_name, output)
-        mock__map.assert_awaited_once_with(group_name, group_size, mock_func, arg_iter, 0,
+        mock__map.assert_awaited_once_with(group_name, num_concurrent, mock_func, arg_iter, 0,
                                            end_callback=end_cb, cancel_callback=cancel_cb)
         mock__generate_group_name.assert_not_called()
 
         mock__map.reset_mock()
-        output = await self.task_pool.map(mock_func, arg_iter, group_size, None, end_cb, cancel_cb)
+        output = await self.task_pool.map(mock_func, arg_iter, num_concurrent, None, end_cb, cancel_cb)
         self.assertEqual(generated_name, output)
-        mock__map.assert_awaited_once_with(generated_name, group_size, mock_func, arg_iter, 0,
+        mock__map.assert_awaited_once_with(generated_name, num_concurrent, mock_func, arg_iter, 0,
                                            end_callback=end_cb, cancel_callback=cancel_cb)
         mock__generate_group_name.assert_called_once_with('map', mock_func)
 
@@ -708,18 +675,18 @@ class TaskPoolTestCase(CommonTestCase):
     async def test_starmap(self, mock__generate_group_name: MagicMock, mock__map: AsyncMock):
         mock__generate_group_name.return_value = generated_name = 'name 1 2 3'
         mock_func = MagicMock()
-        args_iter, group_size, group_name = ([FOO], [BAR]), 2, FOO + BAR
+        args_iter, num_concurrent, group_name = ([FOO], [BAR]), 2, FOO + BAR
         end_cb, cancel_cb = MagicMock(), MagicMock()
-        output = await self.task_pool.starmap(mock_func, args_iter, group_size, group_name, end_cb, cancel_cb)
+        output = await self.task_pool.starmap(mock_func, args_iter, num_concurrent, group_name, end_cb, cancel_cb)
         self.assertEqual(group_name, output)
-        mock__map.assert_awaited_once_with(group_name, group_size, mock_func, args_iter, 1,
+        mock__map.assert_awaited_once_with(group_name, num_concurrent, mock_func, args_iter, 1,
                                            end_callback=end_cb, cancel_callback=cancel_cb)
         mock__generate_group_name.assert_not_called()
 
         mock__map.reset_mock()
-        output = await self.task_pool.starmap(mock_func, args_iter, group_size, None, end_cb, cancel_cb)
+        output = await self.task_pool.starmap(mock_func, args_iter, num_concurrent, None, end_cb, cancel_cb)
         self.assertEqual(generated_name, output)
-        mock__map.assert_awaited_once_with(generated_name, group_size, mock_func, args_iter, 1,
+        mock__map.assert_awaited_once_with(generated_name, num_concurrent, mock_func, args_iter, 1,
                                            end_callback=end_cb, cancel_callback=cancel_cb)
         mock__generate_group_name.assert_called_once_with('starmap', mock_func)
 
@@ -728,18 +695,18 @@ class TaskPoolTestCase(CommonTestCase):
     async def test_doublestarmap(self, mock__generate_group_name: MagicMock, mock__map: AsyncMock):
         mock__generate_group_name.return_value = generated_name = 'name 1 2 3'
         mock_func = MagicMock()
-        kwargs_iter, group_size, group_name = [{'a': FOO}, {'a': BAR}], 2, FOO + BAR
+        kw_iter, num_concurrent, group_name = [{'a': FOO}, {'a': BAR}], 2, FOO + BAR
         end_cb, cancel_cb = MagicMock(), MagicMock()
-        output = await self.task_pool.doublestarmap(mock_func, kwargs_iter, group_size, group_name, end_cb, cancel_cb)
+        output = await self.task_pool.doublestarmap(mock_func, kw_iter, num_concurrent, group_name, end_cb, cancel_cb)
         self.assertEqual(group_name, output)
-        mock__map.assert_awaited_once_with(group_name, group_size, mock_func, kwargs_iter, 2,
+        mock__map.assert_awaited_once_with(group_name, num_concurrent, mock_func, kw_iter, 2,
                                            end_callback=end_cb, cancel_callback=cancel_cb)
         mock__generate_group_name.assert_not_called()
 
         mock__map.reset_mock()
-        output = await self.task_pool.doublestarmap(mock_func, kwargs_iter, group_size, None, end_cb, cancel_cb)
+        output = await self.task_pool.doublestarmap(mock_func, kw_iter, num_concurrent, None, end_cb, cancel_cb)
         self.assertEqual(generated_name, output)
-        mock__map.assert_awaited_once_with(generated_name, group_size, mock_func, kwargs_iter, 2,
+        mock__map.assert_awaited_once_with(generated_name, num_concurrent, mock_func, kw_iter, 2,
                                            end_callback=end_cb, cancel_callback=cancel_cb)
         mock__generate_group_name.assert_called_once_with('doublestarmap', mock_func)
 

usage/USAGE.md

@@ -41,7 +41,7 @@ async def main() -> None:
     pool = SimpleTaskPool(work, args=(5,))  # initializes the pool; no work is being done yet
     await pool.start(3)  # launches work tasks 0, 1, and 2
     await asyncio.sleep(1.5)  # lets the tasks work for a bit
-    await pool.start()  # launches work task 3
+    await pool.start(1)  # launches work task 3
     await asyncio.sleep(1.5)  # lets the tasks work for a bit
     pool.stop(2)  # cancels tasks 3 and 2 (LIFO order)
     pool.lock()  # required for the last line
@@ -135,7 +135,7 @@ async def main() -> None:
     # Once there is room in the pool again, the third and fourth will each start (with IDs 4 and 5)
     # only once there is room in the pool and no more than one other task of these new ones is running.
     args_list = [(0, 10), (10, 20), (20, 30), (30, 40)]
-    await pool.starmap(other_work, args_list, group_size=2)
+    await pool.starmap(other_work, args_list, num_concurrent=2)
     print("> Called `starmap`")
     # Now we lock the pool, so that we can safely await all our tasks.
     pool.lock()
@@ -199,7 +199,7 @@ Started TaskPool-0_Task-3
 > other_work with 15
 Ended TaskPool-0_Task-0
 Ended TaskPool-0_Task-1    <--- these two end and free up two more slots in the pool
-Started TaskPool-0_Task-4    <--- since the group size is set to 2, Task-5 will not start
+Started TaskPool-0_Task-4    <--- since `num_concurrent` is set to 2, Task-5 will not start
 > work with 190
 > work with 190
 > other_work with 16