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Code source de axqua.jobs.launcher
"""Starting a job that outlives whatever started it.
This is the interface plan §8 asks for, and the reason it is an interface rather than one
implementation is that "detached" means four genuinely different things:
* **systemd user services** on Linux, where the kernel already provides the thing this
module wants - a named unit whose whole cgroup can be queried, killed and logged as a
unit. MPI ranks belong to it automatically.
* **A new POSIX session** everywhere else, where the process group is the unit.
* **A Windows Job Object**, because Windows has no process groups in the POSIX sense and
without a Job Object there is no reliable tree-kill at all.
* **WSL**, where the job must be detached *inside* the distro and the Windows side acts
on it only by running commands through ``wsl.exe``.
Two rules cut across all four:
**The environment goes on the process, not into a wrapper shell.** Every launcher takes
an already-captured environment dict (:meth:`SolverEnvironment.capture`) and sets it
directly. A ``bash -lc 'source ...; axqua execute'`` in the middle would add a layer
between the unit and the ranks, and each such layer is somewhere a signal can fail to
propagate.
**A handle must survive the launching process.** Everything needed to query or cancel the
job later - unit name, pid, pgid, job-object name, the recording host and boot id - is
serialized into ``status.json``. A fresh ``axqua cancel`` days later reconstructs the
launcher from that alone.
"""
from __future__ import annotations
import logging
import os
from dataclasses import dataclass, field
from enum import Enum
from pathlib import Path
from typing import Any, Protocol, runtime_checkable
from axqua.core.environment import EnvironmentKind, SolverEnvironment
from axqua.core.errors import ConfigError
from axqua.jobs import procs
from axqua.jobs.model import utc_now
log = logging.getLogger("axqua.jobs.launcher")
__all__ = ["JobLauncher", "LaunchHandle", "LaunchState", "available_launchers",
"launcher_for", "select_launcher"]
[docs]
class LaunchState(str, Enum):
"""What the launcher can say about a handle.
``UNKNOWN`` is a real answer and is treated as "still running" by the reaper.
Reporting a job dead because its supervisor was momentarily unreachable would be
worse than saying nothing.
"""
RUNNING = "running"
GONE = "gone"
UNKNOWN = "unknown"
[docs]
@dataclass
class LaunchHandle:
"""Everything needed to find the job again from a different process."""
backend: str
pid: int | None = None
pgid: int | None = None
proc_started: float | None = None
unit: str | None = None
job_object: str | None = None
distro: str | None = None
host: str = field(default_factory=procs.host_id)
boot_id: str | None = field(default_factory=procs.boot_id)
started: str = field(default_factory=utc_now)
log_path: str | None = None
[docs]
def as_dict(self) -> dict[str, Any]:
return {"backend": self.backend, "pid": self.pid, "pgid": self.pgid,
"proc_started": self.proc_started, "unit": self.unit,
"job_object": self.job_object, "distro": self.distro,
"host": self.host, "boot_id": self.boot_id, "started": self.started,
"log_path": self.log_path}
[docs]
@classmethod
def from_dict(cls, data: dict[str, Any]) -> "LaunchHandle":
known = {f for f in cls.__dataclass_fields__}
return cls(**{k: v for k, v in dict(data or {}).items() if k in known})
[docs]
@runtime_checkable
class JobLauncher(Protocol):
name: str
[docs]
@classmethod
def available(cls, env: SolverEnvironment | None = None) -> bool:
"""Can this launcher be used on this machine, right now?"""
...
[docs]
def submit(self, job_dir: Any, argv: list[str], *, env: dict[str, str],
cwd: Path | str) -> LaunchHandle:
...
# ------------------------------------------------------------------------ selection
#: Env override, so a machine with a broken user manager can be told to skip systemd
#: without editing a profile.
ENV_LAUNCHER = "AXQUA_LAUNCHER"
def _registry() -> dict[str, type]:
from axqua.jobs.launchers.posix import PosixDetachedLauncher
from axqua.jobs.launchers.systemd import SystemdUserLauncher
from axqua.jobs.launchers.windows import WindowsJobObjectLauncher
from axqua.jobs.launchers.wsl import WslLauncher
return {"systemd": SystemdUserLauncher, "posix": PosixDetachedLauncher,
"windows": WindowsJobObjectLauncher, "wsl": WslLauncher}
[docs]
def available_launchers(env: SolverEnvironment | None = None) -> list[str]:
"""Which launchers this machine can actually use. For ``axqua profiles``."""
return [name for name, cls in _registry().items() if cls.available(env)]
[docs]
def select_launcher(env: SolverEnvironment | None = None, *,
prefer: str | None = None) -> JobLauncher:
"""Pick a launcher, first hit wins.
The WSL rule is a **forced** match rather than a preference: a captured Linux
environment cannot start a Windows process, so a WSL solver has exactly one way to
be launched and letting a preference override it would produce a job that cannot
run.
"""
registry = _registry()
prefer = prefer or os.environ.get(ENV_LAUNCHER) or None
if env is not None and env.kind is EnvironmentKind.WSL:
if prefer and prefer not in ("auto", "wsl"):
log.warning("ignoring launcher %r: a wsl environment must be launched "
"inside the distro", prefer)
return registry["wsl"]()
if prefer and prefer != "auto":
cls = registry.get(prefer)
if cls is None:
raise ConfigError(
f"unknown launcher {prefer!r}",
subject="launcher",
remedy="Use one of: auto, " + ", ".join(registry),
)
if not cls.available(env):
raise ConfigError(
f"the {prefer!r} launcher is not available on this machine",
subject="launcher",
remedy="Available here: " + (", ".join(available_launchers(env))
or "none"),
)
return cls()
if os.name == "nt":
return registry["windows"]()
if registry["systemd"].available(env):
return registry["systemd"]()
return registry["posix"]()
[docs]
def launcher_for(handle: LaunchHandle) -> JobLauncher:
"""Reconstruct the launcher that started a recorded job.
By name, from the handle - not by re-running the selection. A job launched under
systemd must be cancelled through systemd even if the user manager has since become
unavailable and selection would now choose the POSIX fallback.
"""
cls = _registry().get(handle.backend)
if cls is None:
raise ConfigError(
f"job was launched with an unknown launcher {handle.backend!r}",
subject="launcher.backend",
remedy="This job may have been launched by a different axqua version.",
)
return cls()
# -------------------------------------------------------------------------- helpers
def runner_argv(job_dir: Path | str) -> list[str]:
"""The command a launcher starts: ``python -m axqua execute <job dir>``, with the
interpreter that is submitting the job.
A job has to run in the environment it was submitted from. This used to start
whichever ``axqua`` came first on ``PATH``, and that is another program as soon as
two environments carry aXqua: the QGIS plugin calls one by its full path while
``PATH`` offers the other. The job then ran with a different Python and different
package versions than the user had chosen, and nothing said so. A calibration
submitted from the environment that holds the required HydroBayesCal ran in the
base environment against an older checkout of it.
The module form also needs no console script on ``PATH``, which a systemd unit
whose environment came from a solver setup script does not have.
"""
import sys
return [sys.executable, "-m", "axqua", "execute", str(job_dir)]
def write_env_file(path: Path | str, env: dict[str, str]) -> Path:
"""Write a systemd-style ``KEY=value`` environment file.
Line-based, so a value containing a newline cannot be represented. Those are dropped
**and logged** rather than silently mangled - a truncated ``PATH`` produces a job
that fails much later with an inexplicable "command not found".
"""
target = Path(path)
target.parent.mkdir(parents=True, exist_ok=True)
lines, skipped = [], []
for key, value in sorted(env.items()):
text = str(value)
if "\n" in text or "\r" in text or "\0" in text:
skipped.append(key)
continue
lines.append(f"{key}={text}")
if skipped:
log.warning("dropped %d environment variable(s) whose value spans lines: %s",
len(skipped), ", ".join(skipped))
target.write_text("\n".join(lines) + "\n", encoding="utf-8")
try:
target.chmod(0o600) # a captured environment can carry credentials
except OSError: # pragma: no cover
pass
return target