utils/async: Add new utils.async module

Home for async-related utilities.

devlib/utils/asyn.py

@@ -0,0 +1,356 @@
+#    Copyright 2013-2018 ARM Limited
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+
+"""
+Async-related utilities
+"""
+
+import abc
+import asyncio
+import functools
+import itertools
+import contextlib
+import pathlib
+import os.path
+
+# Allow nesting asyncio loops, which is necessary for:
+# * Being able to call the blocking variant of a function from an async
+#   function for backward compat
+# * Critically, run the blocking variant of a function in a Jupyter notebook
+#   environment, since it also uses asyncio.
+#
+# Maybe there is still hope for future versions of Python though:
+# https://bugs.python.org/issue22239
+import nest_asyncio
+nest_asyncio.apply()
+
+
+def create_task(awaitable, name=None):
+    if isinstance(awaitable, asyncio.Task):
+        task = awaitable
+    else:
+        task = asyncio.create_task(awaitable)
+    if name is None:
+        name = getattr(awaitable, '__qualname__', None)
+    task.name = name
+    return task
+
+
+class AsyncManager:
+    def __init__(self):
+        self.task_tree = dict()
+        self.resources = dict()
+
+    def track_access(self, access):
+        """
+        Register the given ``access`` to have been handled by the current
+        async task.
+
+        :param access: Access that were done.
+        :type access: ConcurrentAccessBase
+
+        This allows :func:`concurrently` to check that concurrent tasks did not
+        step on each other's toes.
+        """
+        try:
+            task = asyncio.current_task()
+        except RuntimeError:
+            pass
+        else:
+            self.resources.setdefault(task, set()).add(access)
+
+    async def concurrently(self, awaitables):
+        """
+        Await concurrently for the given awaitables, and cancel them as soon as
+        one raises an exception.
+        """
+        awaitables = list(awaitables)
+
+        # Avoid creating asyncio.Tasks when it's not necessary, as it will
+        # disable a the blocking path optimization of Target._execute_async()
+        # that uses blocking calls as long as there is only one asyncio.Task
+        # running on the event loop.
+        if len(awaitables) == 1:
+            return [await awaitables[0]]
+
+        tasks = list(map(create_task, awaitables))
+
+        current_task = asyncio.current_task()
+        task_tree = self.task_tree
+
+        try:
+            node = task_tree[current_task]
+        except KeyError:
+            is_root_task = True
+            node = set()
+        else:
+            is_root_task = False
+        task_tree[current_task] = node
+
+        task_tree.update({
+            child: set()
+            for child in tasks
+        })
+        node.update(tasks)
+
+        try:
+            return await asyncio.gather(*tasks)
+        except BaseException:
+            for task in tasks:
+                task.cancel()
+            raise
+        finally:
+
+            def get_children(task):
+                immediate_children = task_tree[task]
+                return frozenset(
+                    itertools.chain(
+                        [task],
+                        immediate_children,
+                        itertools.chain.from_iterable(
+                            map(get_children, immediate_children)
+                        )
+                    )
+                )
+
+            # Get the resources created during the execution of each subtask
+            # (directly or indirectly)
+            resources = {
+                task: frozenset(
+                    itertools.chain.from_iterable(
+                        self.resources.get(child, [])
+                        for child in get_children(task)
+                    )
+                )
+                for task in tasks
+            }
+            for (task1, resources1), (task2, resources2) in itertools.combinations(resources.items(), 2):
+                for res1, res2 in itertools.product(resources1, resources2):
+                    if issubclass(res2.__class__, res1.__class__) and res1.overlap_with(res2):
+                        raise RuntimeError(
+                            'Overlapping resources manipulated in concurrent async tasks: {} (task {}) and {} (task {})'.format(res1, task1.name, res2, task2.name)
+                        )
+
+            if is_root_task:
+                self.resources.clear()
+                task_tree.clear()
+
+    async def map_concurrently(self, f, keys):
+        """
+        Similar to :meth:`concurrently`,
+        but maps the given function ``f`` on the given ``keys``.
+
+        :return: A dictionary with ``keys`` as keys, and function result as
+            values.
+        """
+        keys = list(keys)
+        return dict(zip(
+            keys,
+            await self.concurrently(map(f, keys))
+        ))
+
+
+def compose(*coros):
+    """
+    Compose coroutines, feeding the output of each as the input of the next
+    one.
+
+    ``await compose(f, g)(x)`` is equivalent to ``await f(await g(x))``
+
+    .. note:: In Haskell, ``compose f g h`` would be equivalent to ``f <=< g <=< h``
+    """
+    async def f(*args, **kwargs):
+        empty_dict = {}
+        for coro in reversed(coros):
+            x = coro(*args, **kwargs)
+            # Allow mixing corountines and regular functions
+            if asyncio.isfuture(x):
+                x = await x
+            args = [x]
+            kwargs = empty_dict
+
+        return x
+    return f
+
+
+class _AsyncPolymorphicFunction:
+    """
+    A callable that allows exposing both a synchronous and asynchronous API.
+
+    When called, the blocking synchronous operation is called. The ```asyn``
+    attribute gives access to the asynchronous version of the function, and all
+    the other attribute access will be redirected to the async function.
+    """
+    def __init__(self, asyn, blocking):
+        self.asyn = asyn
+        self.blocking = blocking
+
+    def __get__(self, *args, **kwargs):
+        return self.__class__(
+            asyn=self.asyn.__get__(*args, **kwargs),
+            blocking=self.blocking.__get__(*args, **kwargs),
+        )
+
+    def __call__(self, *args, **kwargs):
+        return self.blocking(*args, **kwargs)
+
+    def __getattr__(self, attr):
+        return getattr(self.asyn, attr)
+
+
+def asyncf(f):
+    """
+    Decorator used to turn a coroutine into a blocking function, with an
+    optional asynchronous API.
+
+    **Example**::
+
+        @asyncf
+        async def foo(x):
+            await do_some_async_things(x)
+            return x
+
+        # Blocking call, just as if the function was synchronous, except it may
+        # use asynchronous code inside, e.g. to do concurrent operations.
+        foo(42)
+
+        # Asynchronous API, foo.asyn being a corountine
+        await foo.asyn(42)
+
+    This allows the same implementation to be both used as blocking for ease of
+    use and backward compatibility, or exposed as a corountine for callers that
+    can deal with awaitables.
+    """
+    @functools.wraps(f)
+    def blocking(*args, **kwargs):
+        # Since run() needs a corountine, make sure we provide one
+        async def wrapper():
+            x = f(*args, **kwargs)
+            # Async generators have to be consumed and accumulated in a list
+            # before crossing a blocking boundary.
+            if inspect.isasyncgen(x):
+
+                def genf():
+                    asyncgen = x.__aiter__()
+                    while True:
+                        try:
+                            yield asyncio.run(asyncgen.__anext__())
+                        except StopAsyncIteration:
+                            return
+
+                return genf()
+            else:
+                return await x
+        return asyncio.run(wrapper())
+
+    return _AsyncPolymorphicFunction(
+        asyn=f,
+        blocking=blocking,
+    )
+
+
+class _AsyncPolymorphicCM:
+    """
+    Wrap an async context manager such that it exposes a synchronous API as
+    well for backward compatibility.
+    """
+    def __init__(self, async_cm):
+        self.cm = async_cm
+
+    def __aenter__(self, *args, **kwargs):
+        return self.cm.__aenter__(*args, **kwargs)
+
+    def __aexit__(self, *args, **kwargs):
+        return self.cm.__aexit__(*args, **kwargs)
+
+    def __enter__(self, *args, **kwargs):
+        return asyncio.run(self.cm.__aenter__(*args, **kwargs))
+
+    def __exit__(self, *args, **kwargs):
+        return asyncio.run(self.cm.__aexit__(*args, **kwargs))
+
+
+def asynccontextmanager(f):
+    """
+    Same as :func:`contextlib.asynccontextmanager` except that it can also be
+    used with a regular ``with`` statement for backward compatibility.
+    """
+    f = contextlib.asynccontextmanager(f)
+
+    @functools.wraps(f)
+    def wrapper(*args, **kwargs):
+        cm = f(*args, **kwargs)
+        return _AsyncPolymorphicCM(cm)
+
+    return wrapper
+
+
+class ConcurrentAccessBase(abc.ABC):
+    """
+    Abstract Base Class for resources tracked by :func:`concurrently`.
+    """
+    @abc.abstractmethod
+    def overlap_with(self, other):
+        """
+        Return ``True`` if the resource overlaps with the given one.
+
+        :param other: Resources that should not overlap with ``self``.
+        :type other: devlib.utils.asym.ConcurrentAccessBase
+
+        .. note:: It is guaranteed that ``other`` will be a subclass of our
+            class.
+        """
+
+class PathAccess(ConcurrentAccessBase):
+    """
+    Concurrent resource representing a file access.
+
+    :param namespace: Identifier of the namespace of the path. One of "target" or "host".
+    :type namespace: str
+
+    :param path: Normalized path to the file.
+    :type path: str
+
+    :param mode: Opening mode of the file. Can be ``"r"`` for read and ``"w"``
+        for writing.
+    :type mode: str
+    """
+    def __init__(self, namespace, path, mode):
+        assert namespace in ('host', 'target')
+        self.namespace = namespace
+        assert mode in ('r', 'w')
+        self.mode = mode
+        self.path = os.path.abspath(path) if namespace == 'host' else os.path.normpath(path)
+
+    def overlap_with(self, other):
+        path1 = pathlib.Path(self.path).resolve()
+        path2 = pathlib.Path(other.path).resolve()
+        return (
+            self.namespace == other.namespace and
+            'w' in (self.mode, other.mode) and
+            (
+                path1 == path2 or
+                path1 in path2.parents or
+                path2 in path1.parents
+            )
+        )
+
+    def __str__(self):
+        mode = {
+            'r': 'read',
+            'w': 'write',
+        }[self.mode]
+        return '{} ({})'.format(self.path, mode)

setup.py

@@ -94,6 +94,7 @@ params = dict(
         'numpy',
         'pandas',
         'lxml', # More robust xml parsing
+        'nest_asyncio', # Allows running nested asyncio loops
     ],
     extras_require={
         'daq': ['daqpower>=2'],