Review on #83595 flagged two service-lifecycle gaps in the hermes-serve
restart support:
- The unit-name gate accepted anything starting with "hermes-serve",
which also matched the unrelated hermes-server.service. Require the
exact base unit or the hyphenated profile family instead.
- The fleet-restart loop and _finish_dashboard_update_cleanup() could
both restart the same hermes-serve unit — the loop restarts it
directly, then cleanup's PID scan finds the fresh process and
restarts its owning unit again. Thread the fleet loop's restarted
unit names through to _kill_stale_dashboard_processes() so it skips
units already handled.
subprocess.run(capture_output=True, timeout=N) is not hang-safe on
Windows: after the timeout fires, run()'s cleanup kills the direct child
and then joins the pipe reader threads with an UNBOUNDED communicate().
A descendant (conhost.exe under wmic/powershell) holding duplicated pipe
handles keeps the pipes from EOF and the join never returns.
_scan_gateway_pids() runs its wmic / Get-CimInstance Win32_Process scans
exactly that way, and on machines where the full process scan genuinely
exceeds its 10/15s budget (cold WMI on first boot, ARM VMs, heavy
Update/AV activity) hermes update wedged forever inside
_pause_windows_gateways_for_update() before printing a single line —
observed live on a fresh Windows 11 ARM64 VM with a faulthandler stack
pinning the main thread in subprocess._communicate and only a conhost.exe
child surviving. The single-flight update lock then blocks retries until
the wedged process is killed by hand.
This is the same deadlock class bounded_git_probe already fixed for git
probes (#68609 / #66037). Generalize that proven pattern into a shared
bounded_probe_run() — explicit communicate(timeout), kill_process_tree on
failure, bounded 1s drain, then abandon the daemonic readers — and
migrate the whole call-site class onto it:
- hermes_cli/gateway.py _scan_gateway_pids (the site that hung; reached
from hermes update, cron, gateway restart/status, dashboard)
- hermes_cli/dashboard_procs.py wmic scan (same shape, reached on update)
- hermes_cli/claw.py tasklist + PowerShell probes (same shape; its
try/except cannot catch a hang because a hang raises nothing)
- bounded_git_probe now delegates to bounded_probe_run (identical
contract, one copy of the cleanup logic)
Unlike bounded_git_probe, bounded_probe_run returns the CompletedProcess
(or None) rather than collapsing to stdout, because the gateway scan
branches on returncode to trip its wmic -> powershell fallback.
Tests: tests/hermes_cli/test_bounded_probe_run.py covers success,
nonzero-exit passthrough, spawn failure, bounded timeout (fails against
the old unbounded semantics — verified by sabotage), errors= decoding,
DEVNULL stdin, POSIX process-group placement, and the bounded_git_probe
delegation contract. Existing test_git_probe_tree_kill.py passes
unchanged against the delegated implementation.
Closes#87134
Filter manual dashboard/serve respawn candidates after update: skip
ephemeral --port 0 backends (Desktop-owned), dedupe normalized cmdlines,
and cap one restart per profile/HERMES_HOME so orphan counts no longer
grow across successive updates.
os.kill(pid, 0) sends CTRL_C_EVENT on Windows (bpo-14484). The reap path
is POSIX-only, but the blocking lint rejects the pattern repo-wide and
psutil is a core dependency.
Production incident: the orphan reap killed a legitimate SSH remote backend
started by another client machine. Its process sat at ppid 1 with the same
cmdline shape as a genuine orphan, and the exclusion list only covered THIS
app instance's children — ownership by OTHER clients was invisible.
The reap now treats every backend.lock.json under ~/.hermes/desktop-ssh/*/
as an ownership claim: lock payloads are schema-validated (mirroring
remote-lifecycle.ts) and their PIDs are excluded both before the scan and
re-checked after it (defense in depth against a lock written mid-scan).
Regression tests cover the exact incident shape: a lock-owned PID and a
genuine orphan with identical process shapes — only the orphan is reaped.
Also: fold the new single-field `runtime` config category into `agent`
(_CATEGORY_MERGE) and fix an env leak in the serve-startup test
(HERMES_SERVE_HEADLESS restored via monkeypatch) so the combined suites
run green in any order.
When Desktop exits uncleanly, leftover `hermes serve --host 127.0.0.1 --port 0`
processes can be reparented to pid 1 and keep full MCP trees alive. The next
boot then stacks another backend on top of the corpses until EMFILE kills
sidebar/session APIs and tabs disappear.
- Detect Desktop-local serve shape (loopback + ephemeral port 0)
- Only reap processes whose ppid is 0/1 (true orphans)
- Spare fixed-port remote serves (e.g. --port 9119) and HERMES_DESKTOP_CHILD_PID
- Run at Desktop backend start (HERMES_DESKTOP=1) before parent-death watchdog
Complements parent-death watchdog (prevents future orphans) and configurable
nofile soft limit (capacity floor). Together these stop the multi-backend
pile-up cascade observed on macOS Desktop SSH/local installs.
chelsealong