|  | 
|  | 1 | +.. currentmodule:: asyncio | 
|  | 2 | + | 
|  | 3 | + | 
|  | 4 | +.. _asyncio-graph: | 
|  | 5 | + | 
|  | 6 | +======================== | 
|  | 7 | +Call Graph Introspection | 
|  | 8 | +======================== | 
|  | 9 | + | 
|  | 10 | +**Source code:** :source:`Lib/asyncio/graph.py` | 
|  | 11 | + | 
|  | 12 | +------------------------------------- | 
|  | 13 | + | 
|  | 14 | +asyncio has powerful runtime call graph introspection utilities | 
|  | 15 | +to trace the entire call graph of a running *coroutine* or *task*, or | 
|  | 16 | +a suspended *future*.  These utilities and the underlying machinery | 
|  | 17 | +can be used from within a Python program or by external profilers | 
|  | 18 | +and debuggers. | 
|  | 19 | + | 
|  | 20 | +.. versionadded:: next | 
|  | 21 | + | 
|  | 22 | + | 
|  | 23 | +.. function:: print_call_graph(future=None, /, *, file=None, depth=1, limit=None) | 
|  | 24 | + | 
|  | 25 | +   Print the async call graph for the current task or the provided | 
|  | 26 | +   :class:`Task` or :class:`Future`. | 
|  | 27 | + | 
|  | 28 | +   This function prints entries starting from the top frame and going | 
|  | 29 | +   down towards the invocation point. | 
|  | 30 | + | 
|  | 31 | +   The function receives an optional *future* argument. | 
|  | 32 | +   If not passed, the current running task will be used. | 
|  | 33 | + | 
|  | 34 | +   If the function is called on *the current task*, the optional | 
|  | 35 | +   keyword-only *depth* argument can be used to skip the specified | 
|  | 36 | +   number of frames from top of the stack. | 
|  | 37 | + | 
|  | 38 | +   If the optional keyword-only *limit* argument is provided, each call stack | 
|  | 39 | +   in the resulting graph is truncated to include at most ``abs(limit)`` | 
|  | 40 | +   entries. If *limit* is positive, the entries left are the closest to | 
|  | 41 | +   the invocation point. If *limit* is negative, the topmost entries are | 
|  | 42 | +   left. If *limit* is omitted or ``None``, all entries are present. | 
|  | 43 | +   If *limit* is ``0``, the call stack is not printed at all, only | 
|  | 44 | +   "awaited by" information is printed. | 
|  | 45 | + | 
|  | 46 | +   If *file* is omitted or ``None``, the function will print | 
|  | 47 | +   to :data:`sys.stdout`. | 
|  | 48 | + | 
|  | 49 | +   **Example:** | 
|  | 50 | + | 
|  | 51 | +   The following Python code: | 
|  | 52 | + | 
|  | 53 | +   .. code-block:: python | 
|  | 54 | +
 | 
|  | 55 | +      import asyncio | 
|  | 56 | +
 | 
|  | 57 | +      async def test(): | 
|  | 58 | +          asyncio.print_call_graph() | 
|  | 59 | +
 | 
|  | 60 | +      async def main(): | 
|  | 61 | +          async with asyncio.TaskGroup() as g: | 
|  | 62 | +              g.create_task(test(), name='test') | 
|  | 63 | +
 | 
|  | 64 | +      asyncio.run(main()) | 
|  | 65 | +
 | 
|  | 66 | +   will print:: | 
|  | 67 | + | 
|  | 68 | +      * Task(name='test', id=0x1039f0fe0) | 
|  | 69 | +      + Call stack: | 
|  | 70 | +      |   File 't2.py', line 4, in async test() | 
|  | 71 | +      + Awaited by: | 
|  | 72 | +         * Task(name='Task-1', id=0x103a5e060) | 
|  | 73 | +            + Call stack: | 
|  | 74 | +            |   File 'taskgroups.py', line 107, in async TaskGroup.__aexit__() | 
|  | 75 | +            |   File 't2.py', line 7, in async main() | 
|  | 76 | + | 
|  | 77 | +.. function:: format_call_graph(future=None, /, *, depth=1, limit=None) | 
|  | 78 | + | 
|  | 79 | +   Like :func:`print_call_graph`, but returns a string. | 
|  | 80 | +   If *future* is ``None`` and there's no current task, | 
|  | 81 | +   the function returns an empty string. | 
|  | 82 | + | 
|  | 83 | + | 
|  | 84 | +.. function:: capture_call_graph(future=None, /, *, depth=1, limit=None) | 
|  | 85 | + | 
|  | 86 | +   Capture the async call graph for the current task or the provided | 
|  | 87 | +   :class:`Task` or :class:`Future`. | 
|  | 88 | + | 
|  | 89 | +   The function receives an optional *future* argument. | 
|  | 90 | +   If not passed, the current running task will be used. If there's no | 
|  | 91 | +   current task, the function returns ``None``. | 
|  | 92 | + | 
|  | 93 | +   If the function is called on *the current task*, the optional | 
|  | 94 | +   keyword-only *depth* argument can be used to skip the specified | 
|  | 95 | +   number of frames from top of the stack. | 
|  | 96 | + | 
|  | 97 | +   Returns a ``FutureCallGraph`` data class object: | 
|  | 98 | + | 
|  | 99 | +   * ``FutureCallGraph(future, call_stack, awaited_by)`` | 
|  | 100 | + | 
|  | 101 | +      Where *future* is a reference to a :class:`Future` or | 
|  | 102 | +      a :class:`Task` (or their subclasses.) | 
|  | 103 | + | 
|  | 104 | +      ``call_stack`` is a tuple of ``FrameCallGraphEntry`` objects. | 
|  | 105 | + | 
|  | 106 | +      ``awaited_by`` is a tuple of ``FutureCallGraph`` objects. | 
|  | 107 | + | 
|  | 108 | +   * ``FrameCallGraphEntry(frame)`` | 
|  | 109 | + | 
|  | 110 | +      Where *frame* is a frame object of a regular Python function | 
|  | 111 | +      in the call stack. | 
|  | 112 | + | 
|  | 113 | + | 
|  | 114 | +Low level utility functions | 
|  | 115 | +=========================== | 
|  | 116 | + | 
|  | 117 | +To introspect an async call graph asyncio requires cooperation from | 
|  | 118 | +control flow structures, such as :func:`shield` or :class:`TaskGroup`. | 
|  | 119 | +Any time an intermediate :class:`Future` object with low-level APIs like | 
|  | 120 | +:meth:`Future.add_done_callback() <asyncio.Future.add_done_callback>` is | 
|  | 121 | +involved, the following two functions should be used to inform asyncio | 
|  | 122 | +about how exactly such intermediate future objects are connected with | 
|  | 123 | +the tasks they wrap or control. | 
|  | 124 | + | 
|  | 125 | + | 
|  | 126 | +.. function:: future_add_to_awaited_by(future, waiter, /) | 
|  | 127 | + | 
|  | 128 | +   Record that *future* is awaited on by *waiter*. | 
|  | 129 | + | 
|  | 130 | +   Both *future* and *waiter* must be instances of | 
|  | 131 | +   :class:`Future` or :class:`Task` or their subclasses, | 
|  | 132 | +   otherwise the call would have no effect. | 
|  | 133 | + | 
|  | 134 | +   A call to ``future_add_to_awaited_by()`` must be followed by an | 
|  | 135 | +   eventual call to the :func:`future_discard_from_awaited_by` function | 
|  | 136 | +   with the same arguments. | 
|  | 137 | + | 
|  | 138 | + | 
|  | 139 | +.. function:: future_discard_from_awaited_by(future, waiter, /) | 
|  | 140 | + | 
|  | 141 | +   Record that *future* is no longer awaited on by *waiter*. | 
|  | 142 | + | 
|  | 143 | +   Both *future* and *waiter* must be instances of | 
|  | 144 | +   :class:`Future` or :class:`Task` or their subclasses, otherwise | 
|  | 145 | +   the call would have no effect. | 
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