prefect.utilities.asyncutils
¶
Utilities for interoperability with async functions and workers from various contexts.
GatherIncomplete
¶
Bases: RuntimeError
Used to indicate retrieving gather results before completion
Source code in prefect/utilities/asyncutils.py
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GatherTaskGroup
¶
Bases: TaskGroup
A task group that gathers results.
AnyIO does not include support gather
. This class extends the TaskGroup
interface to allow simple gathering.
See https://github.com/agronholm/anyio/issues/100
This class should be instantiated with create_gather_task_group
.
Source code in prefect/utilities/asyncutils.py
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start
async
¶
Since start
returns the result of task_status.started()
but here we must
return the key instead, we just won't support this method for now.
Source code in prefect/utilities/asyncutils.py
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add_event_loop_shutdown_callback
async
¶
Adds a callback to the given callable on event loop closure. The callable must be a coroutine function. It will be awaited when the current event loop is shutting down.
Requires use of asyncio.run()
which waits for async generator shutdown by
default or explicit call of asyncio.shutdown_asyncgens()
. If the application
is entered with asyncio.run_until_complete()
and the user calls
asyncio.close()
without the generator shutdown call, this will not trigger
callbacks.
asyncio does not provided any other way to clean up a resource when the event loop is about to close.
Source code in prefect/utilities/asyncutils.py
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create_gather_task_group
¶
Create a new task group that gathers results
Source code in prefect/utilities/asyncutils.py
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gather
async
¶
Run calls concurrently and gather their results.
Unlike asyncio.gather
this expects to receive callables not coroutines.
This matches anyio
semantics.
Source code in prefect/utilities/asyncutils.py
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is_async_fn
¶
Returns True
if a function returns a coroutine.
See https://github.com/microsoft/pyright/issues/2142 for an example use
Source code in prefect/utilities/asyncutils.py
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is_async_gen_fn
¶
Returns True
if a function is an async generator.
Source code in prefect/utilities/asyncutils.py
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raise_async_exception_in_thread
¶
Raise an exception in a thread asynchronously.
This will not interrupt long-running system calls like sleep
or wait
.
Source code in prefect/utilities/asyncutils.py
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run_async_from_worker_thread
¶
Runs an async function in the main thread's event loop, blocking the worker thread until completion
Source code in prefect/utilities/asyncutils.py
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run_sync
¶
Runs a coroutine from a synchronous context. A thread will be spawned to run the event loop if necessary, which allows coroutines to run in environments like Jupyter notebooks where the event loop runs on the main thread.
Parameters:
Name | Type | Description | Default |
---|---|---|---|
coroutine |
Coroutine[Any, Any, T]
|
The coroutine to run. |
required |
Returns:
Type | Description |
---|---|
T
|
The return value of the coroutine. |
Example
Basic usage:
async def my_async_function(x: int) -> int:
return x + 1
run_sync(my_async_function(1))
Source code in prefect/utilities/asyncutils.py
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run_sync_in_interruptible_worker_thread
async
¶
Runs a sync function in a new interruptible worker thread so that the main thread's event loop is not blocked
Unlike the anyio function, this performs best-effort cancellation of the
thread using the C API. Cancellation will not interrupt system calls like
sleep
.
Source code in prefect/utilities/asyncutils.py
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run_sync_in_worker_thread
async
¶
Runs a sync function in a new worker thread so that the main thread's event loop is not blocked
Unlike the anyio function, this defaults to a cancellable thread and does not allow passing arguments to the anyio function so users can pass kwargs to their function.
Note that cancellation of threads will not result in interrupted computation, the thread may continue running — the outcome will just be ignored.
Source code in prefect/utilities/asyncutils.py
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sync
¶
Call an async function from a synchronous context. Block until completion.
If in an asynchronous context, we will run the code in a separate loop instead of failing but a warning will be displayed since this is not recommended.
Source code in prefect/utilities/asyncutils.py
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sync_compatible
¶
Converts an async function into a dual async and sync function.
When the returned function is called, we will attempt to determine the best way to enter the async function.
- If in a thread with a running event loop, we will return the coroutine for the caller to await. This is normal async behavior.
- If in a blocking worker thread with access to an event loop in another thread, we will submit the async method to the event loop.
- If we cannot find an event loop, we will create a new one and run the async method then tear down the loop.
Source code in prefect/utilities/asyncutils.py
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