Rewritten devutil.ProcessGroup with proper handling of subprocess deaths
- Terminates instantly when vital process dies (e.g. backend doesn't start) - Derived of TaskGroup, augmenting its functionality with similar semantics
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@@ -2,106 +2,76 @@
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"""Utilities meant for devserver script, used only in source repository with dev deps."""
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import asyncio
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import subprocess
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import sys
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from asyncio.subprocess import Process
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from collections.abc import Awaitable
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from contextlib import suppress
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from pathlib import Path
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from typing import TYPE_CHECKING, Any, Self
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from subprocess import CalledProcessError
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from typing import Any
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from urllib.parse import urlsplit
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from buildutil import find_dev_tool, find_install_tool, logger
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from fastapi_vue.hostutil import parse_endpoint
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if TYPE_CHECKING:
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from collections.abc import Coroutine
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class ProcessGroup(asyncio.TaskGroup):
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"""TaskGroup with structured ownership of async subprocesses."""
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class ProcessGroup:
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"""Manage async subprocesses with automatic cleanup, like TaskGroup for processes."""
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def __init__(self, *, terminate_timeout: float = 10) -> None:
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"""Set the grace period before terminate() escalates to kill()."""
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super().__init__()
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self._terminate_timeout = terminate_timeout
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self._cmds: dict[Process, tuple[str, ...]] = {}
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def __init__(self) -> None:
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"""Initialize empty process tracking."""
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self._procs: list[asyncio.subprocess.Process] = []
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self._cmds: dict[int, str] = {} # pid -> command name
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async def spawn(self, *cmd: str, cwd: str | None = None, vital: bool = False) -> Process:
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"""Spawn and own a subprocess. If a vital process exits, the group cancels."""
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async def spawn(
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self,
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*cmd: str,
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cwd: str | None = None,
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) -> asyncio.subprocess.Process:
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"""Spawn a subprocess and track it."""
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cmd_name = Path(cmd[0]).stem
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logger.info(">>> %s", " ".join([cmd_name, *cmd[1:]]))
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proc = await asyncio.create_subprocess_exec(*cmd, cwd=cwd)
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self._procs.append(proc)
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self._cmds[proc.pid] = cmd_name
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return proc
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async def run() -> None:
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name = Path(cmd[0]).stem
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logger.info(">>> %s", " ".join([name, *cmd[1:]]))
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try:
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proc = await asyncio.create_subprocess_exec(*cmd, cwd=cwd)
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self._cmds[proc] = cmd
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started.set_result(proc)
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except Exception as e: # noqa: BLE001
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started.set_exception(e)
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return
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async def wait(
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self,
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*waitables: "asyncio.subprocess.Process | Coroutine[Any, Any, Any]",
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) -> None:
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"""Wait for processes/coroutines to complete, raise SystemExit on failure."""
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async def wait_proc(proc: asyncio.subprocess.Process) -> None:
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returncode = await proc.wait()
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if returncode != 0:
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cmd_name = self._cmds.get(proc.pid, "unknown")
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raise subprocess.CalledProcessError(returncode, cmd_name)
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tasks = [
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wait_proc(w) if isinstance(w, asyncio.subprocess.Process) else w for w in waitables
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]
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try:
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await asyncio.gather(*tasks)
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except subprocess.CalledProcessError as e:
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logger.warning("%s failed with exit status %d", e.cmd, e.returncode)
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raise SystemExit(1) from None
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async def __aenter__(self) -> Self:
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"""Enter the async context manager."""
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return self
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async def __aexit__(self, exc_type: type[BaseException] | None, *_: object) -> None:
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"""Wait for one process to exit, terminate others, then wait for all."""
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await self._cleanup(immediate=exc_type is not None)
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async def _cleanup(self, *, immediate: bool = False) -> None:
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running = [p for p in self._procs if p.returncode is None]
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if not running:
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return
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if not immediate:
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# Wait for any one process to exit
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with suppress(asyncio.CancelledError):
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await asyncio.wait(
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[asyncio.create_task(p.wait()) for p in running],
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return_when=asyncio.FIRST_COMPLETED,
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)
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# Terminate remaining processes
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for p in self._procs:
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if p.returncode is None:
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try:
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returncode = await proc.wait()
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finally:
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with suppress(ProcessLookupError):
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p.terminate()
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# Wait for all to finish (with overall timeout), shielded from cancellation
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still_running = [p for p in self._procs if p.returncode is None]
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if still_running:
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with suppress(asyncio.CancelledError):
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proc.terminate()
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try:
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await asyncio.shield(
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asyncio.wait_for(
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asyncio.gather(*[p.wait() for p in still_running]),
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timeout=10,
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),
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)
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await asyncio.wait_for(proc.wait(), self._terminate_timeout)
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except TimeoutError:
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for p in self._procs:
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if p.returncode is None:
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with suppress(ProcessLookupError):
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p.kill()
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await p.wait()
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with suppress(ProcessLookupError):
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proc.kill()
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await proc.wait()
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if vital:
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logger.warning("Vital process %s exited", name)
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raise CalledProcessError(returncode, cmd)
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started = asyncio.get_running_loop().create_future()
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self.create_task(run())
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return await asyncio.shield(started)
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async def wait(self, *waitables: Process | Awaitable) -> tuple[Any, ...]:
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"""Wait concurrently and return results in argument order."""
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async def task(w: Process | Awaitable) -> Any: # noqa: ANN401
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if not isinstance(w, Process):
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return await w
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if retcode := await w.wait():
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raise CalledProcessError(retcode, self._cmds[w])
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return retcode
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async with asyncio.TaskGroup() as group:
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tasks = [group.create_task(task(w)) for w in waitables]
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return tuple(task.result() for task in tasks)
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async def http_get_server(url: str, timeout: float) -> str | None: # noqa: ASYNC109
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