Files
multi-agent-mux/.agents/skills/lib_py/pane_lock.py
T
GodopuandClaude Opus 5.5 a9ffedac36 fix(issue-50): review findings of PR #56 on macOS
- admission: a `submit --dry-run` record is marked dry_run and is not an
  open job of its session (review 1e25cf2f F1)
- create: the monitor-row adoption requires the row's server to be the one
  this create spawned on (review 1e25cf2f F2)
- pane lock: retry only on contention (BlockingIOError); the docs say the
  flock lasts while any fd-9 holder (the claim shell and the shim) lives
  (review 66680d9d)
- tests on macOS: real-herdr box HOMEs under /tmp (sun_path is 104 bytes),
  resolved paths, the fake claude reads non-canonical input (MAX_CANON 1024)
  and the pane is read unwrapped; lock holders exec their sleep so killing
  them frees the lock; the adoption tests name the server

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01VCgu9Fa9iT7TbJUSzdq4Ff
2026-10-12 09:03:08 +09:00

103 lines
4.3 KiB
Python

"""Issue #50 follow-up: one pane claim at a time per herdr server.
The herdr shim's `new-session` chooses a pane - an idle one in a workspace on
the same cwd (BUG-4), a split of one, or the root pane of a fresh workspace -
and then claims it with `agent start`. Two shims on one server (several
`create` at once into one folder) could choose the same idle pane in between,
and the later `agent start` failed with agent_pane_busy. The shim now holds
one lock per server from the choice to the claim.
pane_lock.py path --session S the lock file of herdr session S, under the
HOME whose socket the session uses. S empty
(or `default`) is the shim's ambient target:
herdr then answers on the server of the pane
this runs in (HERDR_SESSION / HERDR_SOCKET_PATH,
as lib.sh _herdr_caller_server reads them), or
the default server outside any pane - the
lock is that server's (review e8e471ff R1)
pane_lock.py acquire --fd N flock(LOCK_EX) on the inherited fd N; prints
`locked`, or `timeout` once MAM_PANE_CLAIM_WAIT_S
(default 120, minimum 1) has passed
The lock is a BSD flock, which belongs to the open file on fd 9: it outlives
this helper and ends when the last process holding that fd ends, however it
ends (exit, kill -9), so a dead holder leaves nothing to steal. The holders are
the shell running the claim block and the command it runs (the shim); a child
that outlived them would keep it too, so nothing long-lived may inherit fd 9 -
the herdr server is spawned with close_fds (review 66680d9d). flock(1) is not on
macOS; fcntl.flock is. Stdlib only, Python 3.9.
"""
from __future__ import annotations
import argparse
import fcntl
import os
import sys
import time
from typing import List, Mapping, Optional
from lib_py import ints
DEFAULT_WAIT_S = 120
def caller_server(env: Mapping[str, str]) -> str:
"""The server whose pane this process runs in, by the pane's exports:
HERDR_SESSION when present, else HERDR_SOCKET_PATH's layout
($HOME/.config/herdr/herdr.sock -> default, .../sessions/<name>/herdr.sock
-> name); "" outside a pane or for an unrecognised layout."""
if env.get("HERDR_SESSION"):
return env["HERDR_SESSION"]
sock = env.get("HERDR_SOCKET_PATH") or ""
if sock.endswith("/.config/herdr/herdr.sock"):
return "default"
if sock.endswith("/herdr.sock") and "/.config/herdr/sessions/" in sock:
return sock[:-len("/herdr.sock")].rsplit("/", 1)[-1]
return ""
def lock_path(session: Optional[str], env: Mapping[str, str]) -> str:
home = env.get("HOME") or env.get("HOME_DIR") or os.path.expanduser("~")
if session in (None, "", "default"):
session = caller_server(env) or "default"
return os.path.join(home, ".local", "state", "mam", "pane-lock", session + ".lock")
def wait_s(env: Mapping[str, str]) -> int:
return ints.positive_int(env.get("MAM_PANE_CLAIM_WAIT_S"), 1) or DEFAULT_WAIT_S
def acquire(fd: int, wait: float) -> str:
"""`locked`, or `timeout` when the lock was not free within `wait` s. The
deadline is on the monotonic clock; a step of the wall clock does not
stretch or cut it. Only contention is waited out: any other error (a bad
fd) raises, which the shim reports as an undecided lock."""
deadline = time.monotonic() + wait
while True:
try:
fcntl.flock(fd, fcntl.LOCK_EX | fcntl.LOCK_NB)
return "locked"
except BlockingIOError:
if time.monotonic() >= deadline:
return "timeout"
time.sleep(0.2)
def main(argv: Optional[List[str]] = None) -> int:
p = argparse.ArgumentParser(prog="pane_lock.py")
sub = p.add_subparsers(dest="cmd", required=True)
s = sub.add_parser("path")
s.add_argument("--session", default="")
s = sub.add_parser("acquire")
s.add_argument("--fd", type=int, required=True)
a = p.parse_args(argv)
if a.cmd == "path":
print(lock_path(a.session, os.environ))
else:
print(acquire(a.fd, wait_s(os.environ)))
return 0
if __name__ == "__main__":
sys.exit(main())