|
| 1 | +.. currentmodule:: asyncio |
| 2 | + |
| 3 | +.. _asyncio-introspection-tools: |
| 4 | + |
| 5 | +================================ |
| 6 | +Command-line introspection tools |
| 7 | +================================ |
| 8 | + |
| 9 | +**Source code:** :source:`Lib/asyncio/tools.py` |
| 10 | + |
| 11 | +------------------------------------- |
| 12 | + |
| 13 | +The :mod:`!asyncio` module can be invoked as a script via ``python -m |
| 14 | +asyncio`` to inspect the task graph of another running Python process without |
| 15 | +modifying it or restarting it. The :mod:`!asyncio.tools` submodule implements |
| 16 | +this interface. |
| 17 | + |
| 18 | +The following commands inspect the process identified by ``PID``: |
| 19 | + |
| 20 | +.. code-block:: shell-session |
| 21 | +
|
| 22 | + $ python -m asyncio pstree [--retries N] PID |
| 23 | + $ python -m asyncio ps [--retries N] PID |
| 24 | +
|
| 25 | +The commands read the target process state without executing any code in it. |
| 26 | +They are only available on supported platforms and may require permission to |
| 27 | +inspect another process. See the :ref:`permission-requirements <permission-requirements>` for details. |
| 28 | + |
| 29 | +.. seealso:: |
| 30 | + |
| 31 | + :ref:`asyncio-graph` |
| 32 | + Programmatic APIs for inspecting the async call graph of a task or |
| 33 | + future in the current process. |
| 34 | + |
| 35 | +The command examples below use this program, which creates a task hierarchy |
| 36 | +suitable for inspection and prints its process ID: |
| 37 | + |
| 38 | +.. code-block:: python |
| 39 | + :caption: example.py |
| 40 | +
|
| 41 | + import asyncio |
| 42 | + import os |
| 43 | +
|
| 44 | + async def play(track): |
| 45 | + await asyncio.sleep(3600) |
| 46 | + print(f"🎵 Finished: {track}") |
| 47 | +
|
| 48 | + async def album(name, tracks): |
| 49 | + async with asyncio.TaskGroup() as tg: |
| 50 | + for track in tracks: |
| 51 | + tg.create_task(play(track), name=track) |
| 52 | +
|
| 53 | + async def main(): |
| 54 | + print(f"PID: {os.getpid()}") |
| 55 | + async with asyncio.TaskGroup() as tg: |
| 56 | + tg.create_task( |
| 57 | + album("Sundowning", ["TNDNBTG", "Levitate"]), |
| 58 | + name="Sundowning", |
| 59 | + ) |
| 60 | + tg.create_task( |
| 61 | + album("TMBTE", ["DYWTYLM", "Aqua Regia"]), |
| 62 | + name="TMBTE", |
| 63 | + ) |
| 64 | +
|
| 65 | + asyncio.run(main()) |
| 66 | +
|
| 67 | +Run the program in one terminal and leave it running: |
| 68 | + |
| 69 | +.. code-block:: shell-session |
| 70 | +
|
| 71 | + $ python example.py |
| 72 | + PID: 12345 |
| 73 | +
|
| 74 | +Then pass the printed process ID to the commands from another terminal. |
| 75 | +Thread IDs, task IDs, file paths, and line numbers vary between runs and |
| 76 | +source layouts. |
| 77 | + |
| 78 | +.. versionadded:: 3.14 |
| 79 | + |
| 80 | +Command-line options |
| 81 | +==================== |
| 82 | + |
| 83 | +.. option:: pstree PID |
| 84 | + |
| 85 | + Display task and coroutine relationships as a tree. Each task is shown |
| 86 | + with its full coroutine stack, nested under the task (if any) that is |
| 87 | + awaiting it. This subcommand is useful for quickly identifying which branch |
| 88 | + of a task hierarchy is blocked and where in its coroutine stack execution |
| 89 | + has paused: |
| 90 | + |
| 91 | + .. code-block:: shell-session |
| 92 | +
|
| 93 | + $ python -m asyncio pstree 12345 |
| 94 | + └── (T) Task-1 |
| 95 | + └── main example.py:12 |
| 96 | + └── TaskGroup.__aexit__ Lib/asyncio/taskgroups.py:75 |
| 97 | + └── TaskGroup._aexit Lib/asyncio/taskgroups.py:124 |
| 98 | + ├── (T) Sundowning |
| 99 | + │ └── album example.py:7 |
| 100 | + │ └── TaskGroup.__aexit__ Lib/asyncio/taskgroups.py:75 |
| 101 | + │ └── TaskGroup._aexit Lib/asyncio/taskgroups.py:124 |
| 102 | + │ ├── (T) TNDNBTG |
| 103 | + │ │ └── play example.py:4 |
| 104 | + │ │ └── sleep Lib/asyncio/tasks.py:702 |
| 105 | + │ └── (T) Levitate |
| 106 | + │ └── play example.py:4 |
| 107 | + │ └── sleep Lib/asyncio/tasks.py:702 |
| 108 | + └── (T) TMBTE |
| 109 | + └── album example.py:7 |
| 110 | + └── TaskGroup.__aexit__ Lib/asyncio/taskgroups.py:75 |
| 111 | + └── TaskGroup._aexit Lib/asyncio/taskgroups.py:124 |
| 112 | + ├── (T) DYWTYLM |
| 113 | + │ └── play example.py:4 |
| 114 | + │ └── sleep Lib/asyncio/tasks.py:702 |
| 115 | + └── (T) Aqua Regia |
| 116 | + └── play example.py:4 |
| 117 | + └── sleep Lib/asyncio/tasks.py:702 |
| 118 | +
|
| 119 | + If the await graph contains a cycle, ``pstree`` reports an error instead |
| 120 | + of printing a tree. A cycle in the await graph is unusual and typically |
| 121 | + indicates a programming error: |
| 122 | + |
| 123 | + .. code-block:: shell-session |
| 124 | +
|
| 125 | + $ python -m asyncio pstree 12345 |
| 126 | + ERROR: await-graph contains cycles - cannot print a tree! |
| 127 | +
|
| 128 | + cycle: Task-2 → Task-3 → Task-2 |
| 129 | +
|
| 130 | +.. option:: ps PID |
| 131 | + |
| 132 | + Display a flat table of all pending tasks in the process *PID*. Each row |
| 133 | + shows the event-loop thread ID, task ID and name, coroutine stack, and the |
| 134 | + awaiting task's stack, name, and ID, if any. |
| 135 | + |
| 136 | + This subcommand prints all tasks regardless of whether the await graph |
| 137 | + contains cycles: |
| 138 | + |
| 139 | + .. code-block:: shell-session |
| 140 | +
|
| 141 | + $ python -m asyncio ps 12345 |
| 142 | + tid task id task name coroutine stack awaiter chain awaiter name awaiter id |
| 143 | + ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
| 144 | + 18445801 0x10a456060 Task-1 TaskGroup._aexit -> TaskGroup.__aexit__ -> main 0x0 |
| 145 | + 18445801 0x10a439f60 Sundowning TaskGroup._aexit -> TaskGroup.__aexit__ -> album TaskGroup._aexit -> TaskGroup.__aexit__ -> main Task-1 0x10a456060 |
| 146 | + 18445801 0x10a439d70 TMBTE TaskGroup._aexit -> TaskGroup.__aexit__ -> album TaskGroup._aexit -> TaskGroup.__aexit__ -> main Task-1 0x10a456060 |
| 147 | + 18445801 0x10a2a3a80 TNDNBTG sleep -> play TaskGroup._aexit -> TaskGroup.__aexit__ -> album Sundowning 0x10a439f60 |
| 148 | + 18445801 0x10a2a38a0 Levitate sleep -> play TaskGroup._aexit -> TaskGroup.__aexit__ -> album Sundowning 0x10a439f60 |
| 149 | + 18445801 0x10a2d7150 DYWTYLM sleep -> play TaskGroup._aexit -> TaskGroup.__aexit__ -> album TMBTE 0x10a439d70 |
| 150 | + 18445801 0x10a6bdaa0 Aqua Regia sleep -> play TaskGroup._aexit -> TaskGroup.__aexit__ -> album TMBTE 0x10a439d70 |
| 151 | +
|
| 152 | +.. option:: --retries N |
| 153 | + |
| 154 | + Retry failed attempts to inspect the target process up to *N* times. This |
| 155 | + can help when the target process changes while its state is being read. |
| 156 | + |
| 157 | + .. versionadded:: 3.15 |
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