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from __future__ import annotations
import os
import platform
import threading
from concurrent.futures import FIRST_COMPLETED, Future, ThreadPoolExecutor, wait
from contextlib import ExitStack
from contextvars import copy_context
from datetime import datetime, timezone
from logging import Logger, getLogger
from typing import Callable, Optional
from uuid import UUID
import attrs
from ..abc import DataStore, EventSource
from ..context import current_worker, job_info
from ..enums import JobOutcome, RunState
from ..eventbrokers.local import LocalEventBroker
from ..events import JobAdded, WorkerStarted, WorkerStopped
from ..structures import Job, JobInfo, JobResult
from ..validators import positive_integer
@attrs.define(eq=False)
class Worker:
"""Runs jobs locally in a thread pool."""
data_store: DataStore
max_concurrent_jobs: int = attrs.field(kw_only=True, validator=positive_integer, default=20)
identity: str = attrs.field(kw_only=True, default=None)
logger: Optional[Logger] = attrs.field(kw_only=True, default=getLogger(__name__))
_state: RunState = attrs.field(init=False, default=RunState.stopped)
_wakeup_event: threading.Event = attrs.field(init=False)
_acquired_jobs: set[Job] = attrs.field(init=False, factory=set)
_events: LocalEventBroker = attrs.field(init=False, factory=LocalEventBroker)
_running_jobs: set[UUID] = attrs.field(init=False, factory=set)
_exit_stack: ExitStack = attrs.field(init=False)
_executor: ThreadPoolExecutor = attrs.field(init=False)
def __attrs_post_init__(self) -> None:
if not self.identity:
self.identity = f'{platform.node()}-{os.getpid()}-{id(self)}'
@property
def events(self) -> EventSource:
return self._events
@property
def state(self) -> RunState:
return self._state
def __enter__(self) -> Worker:
self._state = RunState.starting
self._wakeup_event = threading.Event()
self._exit_stack = ExitStack()
self._exit_stack.__enter__()
self._exit_stack.enter_context(self._events)
# Initialize the data store and start relaying events to the worker's event broker
self._exit_stack.enter_context(self.data_store)
self._exit_stack.enter_context(self.data_store.events.subscribe(self._events.publish))
# Wake up the worker if the data store emits a significant job event
self._exit_stack.enter_context(
self.data_store.events.subscribe(lambda event: self._wakeup_event.set(), {JobAdded})
)
# Start the worker and return when it has signalled readiness or raised an exception
start_future: Future[None] = Future()
with self._events.subscribe(start_future.set_result, one_shot=True):
self._executor = ThreadPoolExecutor(1)
run_future = self._executor.submit(copy_context().run, self.run)
wait([start_future, run_future], return_when=FIRST_COMPLETED)
if run_future.done():
run_future.result()
return self
def __exit__(self, exc_type, exc_val, exc_tb):
self._state = RunState.stopping
self._wakeup_event.set()
self._executor.shutdown(wait=exc_type is None)
self._exit_stack.__exit__(exc_type, exc_val, exc_tb)
del self._wakeup_event
def run(self) -> None:
if self._state is not RunState.starting:
raise RuntimeError(f'This function cannot be called while the worker is in the '
f'{self._state} state')
# Set the current worker
token = current_worker.set(self)
# Signal that the worker has started
self._state = RunState.started
self._events.publish(WorkerStarted())
executor = ThreadPoolExecutor(max_workers=self.max_concurrent_jobs)
exception: Optional[BaseException] = None
try:
while self._state is RunState.started:
available_slots = self.max_concurrent_jobs - len(self._running_jobs)
if available_slots:
jobs = self.data_store.acquire_jobs(self.identity, available_slots)
for job in jobs:
task = self.data_store.get_task(job.task_id)
self._running_jobs.add(job.id)
executor.submit(copy_context().run, self._run_job, job, task.func)
self._wakeup_event.wait()
self._wakeup_event = threading.Event()
except BaseException as exc:
self.logger.exception('Worker crashed')
exception = exc
else:
self.logger.info('Worker stopped')
finally:
current_worker.reset(token)
self._state = RunState.stopped
self._events.publish(WorkerStopped(exception=exception))
executor.shutdown()
def _run_job(self, job: Job, func: Callable) -> None:
try:
# Check if the job started before the deadline
start_time = datetime.now(timezone.utc)
if job.start_deadline is not None and start_time > job.start_deadline:
result = JobResult(job_id=job.id, outcome=JobOutcome.missed_start_deadline)
self.data_store.release_job(self.identity, job.task_id, result)
return
token = job_info.set(JobInfo.from_job(job))
try:
retval = func(*job.args, **job.kwargs)
except BaseException as exc:
result = JobResult(job_id=job.id, outcome=JobOutcome.error, exception=exc)
self.data_store.release_job(self.identity, job.task_id, result)
if not isinstance(exc, Exception):
raise
else:
result = JobResult(job_id=job.id, outcome=JobOutcome.success, return_value=retval)
self.data_store.release_job(self.identity, job.task_id, result)
finally:
job_info.reset(token)
finally:
self._running_jobs.remove(job.id)
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