|
| 1 | +import asyncio |
| 2 | + |
| 3 | +from .context import Context as _Context |
| 4 | + |
| 5 | + |
| 6 | +class AsyncContext(_Context): |
| 7 | + """ |
| 8 | + Async Context for storing segments. |
| 9 | +
|
| 10 | + Inherits nearly everything from the main Context class. |
| 11 | + Replaces threading.local with a task based local storage class, |
| 12 | + Also overrides clear_trace_entities |
| 13 | + """ |
| 14 | + def __init__(self, *args, loop=None, use_task_factory=True, **kwargs): |
| 15 | + super(AsyncContext, self).__init__(*args, **kwargs) |
| 16 | + |
| 17 | + self._loop = loop |
| 18 | + if loop is None: |
| 19 | + self._loop = asyncio.get_event_loop() |
| 20 | + |
| 21 | + if use_task_factory: |
| 22 | + self._loop.set_task_factory(task_factory) |
| 23 | + |
| 24 | + self._local = TaskLocalStorage(loop=loop) |
| 25 | + |
| 26 | + def clear_trace_entities(self): |
| 27 | + """ |
| 28 | + Clear all trace_entities stored in the task local context. |
| 29 | + """ |
| 30 | + if self._local is not None: |
| 31 | + self._local.clear() |
| 32 | + |
| 33 | + |
| 34 | +class TaskLocalStorage(object): |
| 35 | + """ |
| 36 | + Simple task local storage |
| 37 | + """ |
| 38 | + def __init__(self, loop=None): |
| 39 | + if loop is None: |
| 40 | + loop = asyncio.get_event_loop() |
| 41 | + self._loop = loop |
| 42 | + |
| 43 | + def __setattr__(self, name, value): |
| 44 | + if name in ('_loop',): |
| 45 | + # Set normal attributes |
| 46 | + object.__setattr__(self, name, value) |
| 47 | + |
| 48 | + else: |
| 49 | + # Set task local attributes |
| 50 | + task = asyncio.Task.current_task(loop=self._loop) |
| 51 | + if task is None: |
| 52 | + return None |
| 53 | + |
| 54 | + if not hasattr(task, 'context'): |
| 55 | + task.context = {} |
| 56 | + |
| 57 | + task.context[name] = value |
| 58 | + |
| 59 | + def __getattribute__(self, item): |
| 60 | + if item in ('_loop', 'clear'): |
| 61 | + # Return references to local objects |
| 62 | + return object.__getattribute__(self, item) |
| 63 | + |
| 64 | + task = asyncio.Task.current_task(loop=self._loop) |
| 65 | + if task is None: |
| 66 | + return None |
| 67 | + |
| 68 | + if hasattr(task, 'context') and item in task.context: |
| 69 | + return task.context[item] |
| 70 | + |
| 71 | + raise AttributeError('Task context does not have attribute {0}'.format(item)) |
| 72 | + |
| 73 | + def clear(self): |
| 74 | + # If were in a task, clear the context dictionary |
| 75 | + task = asyncio.Task.current_task(loop=self._loop) |
| 76 | + if task is not None and hasattr(task, 'context'): |
| 77 | + task.context.clear() |
| 78 | + |
| 79 | + |
| 80 | +def task_factory(loop, coro): |
| 81 | + """ |
| 82 | + Task factory function |
| 83 | +
|
| 84 | + Fuction closely mirrors the logic inside of |
| 85 | + asyncio.BaseEventLoop.create_task. Then if there is a current |
| 86 | + task and the current task has a context then share that context |
| 87 | + with the new task |
| 88 | + """ |
| 89 | + task = asyncio.Task(coro, loop=loop) |
| 90 | + if task._source_traceback: # flake8: noqa |
| 91 | + del task._source_traceback[-1] # flake8: noqa |
| 92 | + |
| 93 | + # Share context with new task if possible |
| 94 | + current_task = asyncio.Task.current_task(loop=loop) |
| 95 | + if current_task is not None and hasattr(current_task, 'context'): |
| 96 | + setattr(task, 'context', current_task.context) |
| 97 | + |
| 98 | + return task |
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