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Extract task management to a separate module (no changes, just a move)
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Sergey Vasilyev
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Jul 24, 2019
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,169 @@ | ||
| import asyncio | ||
| import functools | ||
| import logging | ||
| import signal | ||
| import threading | ||
| from typing import Optional, Callable | ||
|
|
||
| from kopf.engines import peering | ||
| from kopf.engines import posting | ||
| from kopf.reactor import handling | ||
| from kopf.reactor import lifecycles | ||
| from kopf.reactor import queueing | ||
| from kopf.reactor import registries | ||
|
|
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| logger = logging.getLogger(__name__) | ||
|
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|
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| def run( | ||
| loop: Optional[asyncio.AbstractEventLoop] = None, | ||
| lifecycle: Optional[Callable] = None, | ||
| registry: Optional[registries.BaseRegistry] = None, | ||
| standalone: bool = False, | ||
| priority: int = 0, | ||
| peering_name: str = peering.PEERING_DEFAULT_NAME, | ||
| namespace: Optional[str] = None, | ||
| ): | ||
| """ | ||
| Serve the events for all the registered resources and handlers. | ||
| This process typically never ends, unless an unhandled error happens | ||
| in one of the consumers/producers. | ||
| """ | ||
| loop = loop if loop is not None else asyncio.get_event_loop() | ||
| tasks = create_tasks( | ||
| loop=loop, | ||
| lifecycle=lifecycle, | ||
| registry=registry, | ||
| standalone=standalone, | ||
| namespace=namespace, | ||
| priority=priority, | ||
| peering_name=peering_name, | ||
| ) | ||
|
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||
| # Run the infinite tasks until one of them fails/exits (they never exit normally). | ||
| # Give some time for the remaining tasks to handle the cancellations (e.g. via try-finally). | ||
| done1, pending1 = _wait_gracefully(loop, tasks, return_when=asyncio.FIRST_COMPLETED) | ||
| done2, pending2 = _wait_cancelled(loop, pending1) | ||
| done3, pending3 = _wait_gracefully(loop, asyncio.all_tasks(loop), timeout=1.0) | ||
| done4, pending4 = _wait_cancelled(loop, pending3) | ||
|
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||
| # Check the results of the non-cancelled tasks, and re-raise of there were any exceptions. | ||
| # The cancelled tasks are not re-raised, as it is a normal flow. | ||
| _reraise(loop, list(done1) + list(done2) + list(done3) + list(done4)) | ||
|
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|
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| def create_tasks( | ||
| loop: asyncio.AbstractEventLoop, | ||
| lifecycle: Optional[Callable] = None, | ||
| registry: Optional[registries.BaseRegistry] = None, | ||
| standalone: bool = False, | ||
| priority: int = 0, | ||
| peering_name: str = peering.PEERING_DEFAULT_NAME, | ||
| namespace: Optional[str] = None, | ||
| ): | ||
| """ | ||
| Create all the tasks needed to run the operator, but do not spawn/start them. | ||
| The tasks are properly inter-connected depending on the runtime specification. | ||
| They can be injected into any event loop as needed. | ||
| """ | ||
|
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||
| # The freezer and the registry are scoped to this whole task-set, to sync them all. | ||
| lifecycle = lifecycle if lifecycle is not None else lifecycles.get_default_lifecycle() | ||
| registry = registry if registry is not None else registries.get_default_registry() | ||
| event_queue = asyncio.Queue(loop=loop) | ||
| freeze_flag = asyncio.Event(loop=loop) | ||
| should_stop = asyncio.Event(loop=loop) | ||
| tasks = [] | ||
|
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||
| # A top-level task for external stopping by setting a stop-flag. Once set, | ||
| # this task will exit, and thus all other top-level tasks will be cancelled. | ||
| tasks.extend([ | ||
| loop.create_task(_stop_flag_checker(should_stop)), | ||
| ]) | ||
|
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||
| # K8s-event posting. Events are queued in-memory and posted in the background. | ||
| # NB: currently, it is a global task, but can be made per-resource or per-object. | ||
| tasks.extend([ | ||
| loop.create_task(posting.poster( | ||
| event_queue=event_queue)), | ||
| ]) | ||
|
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||
| # Monitor the peers, unless explicitly disabled. | ||
| ourselves: Optional[peering.Peer] = peering.Peer.detect( | ||
| id=peering.detect_own_id(), priority=priority, | ||
| standalone=standalone, namespace=namespace, name=peering_name, | ||
| ) | ||
| if ourselves: | ||
| tasks.extend([ | ||
| loop.create_task(peering.peers_keepalive( | ||
| ourselves=ourselves)), | ||
| loop.create_task(queueing.watcher( | ||
| namespace=namespace, | ||
| resource=ourselves.resource, | ||
| handler=functools.partial(peering.peers_handler, | ||
| ourselves=ourselves, | ||
| freeze=freeze_flag))), # freeze is set/cleared | ||
| ]) | ||
|
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||
| # Resource event handling, only once for every known resource (de-duplicated). | ||
| for resource in registry.resources: | ||
| tasks.extend([ | ||
| loop.create_task(queueing.watcher( | ||
| namespace=namespace, | ||
| resource=resource, | ||
| handler=functools.partial(handling.custom_object_handler, | ||
| lifecycle=lifecycle, | ||
| registry=registry, | ||
| resource=resource, | ||
| event_queue=event_queue, | ||
| freeze=freeze_flag))), # freeze is only checked | ||
| ]) | ||
|
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||
| # On Ctrl+C or pod termination, cancel all tasks gracefully. | ||
| if threading.current_thread() is threading.main_thread(): | ||
| loop.add_signal_handler(signal.SIGINT, should_stop.set) | ||
| loop.add_signal_handler(signal.SIGTERM, should_stop.set) | ||
| else: | ||
| logger.warning("OS signals are ignored: running not in the main thread.") | ||
|
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| return tasks | ||
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| def _wait_gracefully(loop, tasks, *, timeout=None, return_when=asyncio.ALL_COMPLETED): | ||
| if not tasks: | ||
| return [], [] | ||
| try: | ||
| done, pending = loop.run_until_complete(asyncio.wait(tasks, return_when=return_when, timeout=timeout)) | ||
| except asyncio.CancelledError: | ||
| # ``asyncio.wait()`` is cancelled, but the tasks can be running. | ||
| done, pending = [], tasks | ||
| return done, pending | ||
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| def _wait_cancelled(loop, tasks, *, timeout=None): | ||
| for task in tasks: | ||
| task.cancel() | ||
| if tasks: | ||
| done, pending = loop.run_until_complete(asyncio.wait(tasks, return_when=asyncio.ALL_COMPLETED, timeout=timeout)) | ||
| assert not pending | ||
| return done, pending | ||
| else: | ||
| return [], [] | ||
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| def _reraise(loop, tasks): | ||
| for task in tasks: | ||
| try: | ||
| task.result() # can raise the regular (non-cancellation) exceptions. | ||
| except asyncio.CancelledError: | ||
| pass | ||
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| async def _stop_flag_checker(should_stop): | ||
| try: | ||
| await should_stop.wait() | ||
| except asyncio.CancelledError: | ||
| pass # operator is stopping for any other reason | ||
| else: | ||
| logger.debug("Stop-flag is raised. Operator is stopping.") |
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