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aiturk-hermes-ide/tests/hermes_cli/test_mcp_helper_ledger.py
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Python

"""Tests for stdio MCP helper children in the spawn ledger (#61514).
Covers ``register_child`` (the ledger mirror of ``register_self`` for
subprocesses that never import Hermes code), the live-spawner protection
contract, dead-spawner reap eligibility through BOTH consumers (the updater's
``_ledger_reapable_backend_pids`` rung and the startup
``reap_orphaned_mcp_helpers`` sweep), and prune-on-write of exited children.
Uses REAL subprocesses (``sleep``) and the real psutil so the
``(pid, create_time)`` identity pair is exercised end-to-end, with the ledger
redirected to a tmp path.
"""
from __future__ import annotations
import json
import os
import subprocess
import sys
import time
from unittest.mock import patch
import psutil
import pytest
from hermes_cli import process_identity as pi
pytestmark = pytest.mark.skipif(
sys.platform == "win32", reason="uses POSIX sleep children"
)
@pytest.fixture
def ledger(tmp_path):
path = tmp_path / pi.LEDGER_FILENAME
with patch.object(pi, "_ledger_path", return_value=path):
yield path
@pytest.fixture
def child():
"""A real live child process of THIS test process."""
proc = subprocess.Popen(["sleep", "300"])
try:
yield proc
finally:
proc.kill()
proc.wait()
def _dead_process_identity() -> tuple[int, float]:
"""(pid, create_time) of a real process that is provably dead."""
proc = subprocess.Popen(["sleep", "300"])
create = psutil.Process(proc.pid).create_time()
proc.kill()
proc.wait()
# Ensure the corpse is fully reaped (no zombie ambiguity).
deadline = time.time() + 5
while time.time() < deadline and psutil.pid_exists(proc.pid):
time.sleep(0.05)
return proc.pid, create
# ---------------------------------------------------------------------------
# register_child — entry shape
# ---------------------------------------------------------------------------
def test_register_child_entry_shape(ledger, child):
assert pi.register_child(child.pid, "mcp-helper") is True
entries = json.loads(ledger.read_text(encoding="utf-8"))
assert len(entries) == 1
e = entries[0]
assert e["pid"] == child.pid
assert e["purpose"] == "mcp-helper"
assert e["install"] == pi.install_id()
assert e["spawner_pid"] == os.getpid()
assert e["spawner_create"] == pytest.approx(
psutil.Process(os.getpid()).create_time(), abs=2.0
)
assert e["create_time"] == pytest.approx(
psutil.Process(child.pid).create_time(), abs=2.0
)
assert e["registered_at"] == pytest.approx(time.time(), abs=30.0)
# Visible through the live-verified reader too.
live = pi.ledger_entries()
assert [x["pid"] for x in live] == [child.pid]
def test_register_child_rejects_dead_or_invalid_pids(ledger):
dead_pid, _ = _dead_process_identity()
assert pi.register_child(dead_pid, "mcp-helper") is False
assert pi.register_child(0, "mcp-helper") is False
assert pi.register_child(-5, "mcp-helper") is False
assert pi.register_child("junk", "mcp-helper") is False # type: ignore[arg-type]
assert not ledger.exists() or json.loads(ledger.read_text()) == []
def test_mcp_helper_is_reapable_purpose():
assert "mcp-helper" in pi.REAPABLE_PURPOSES
# Interactive purposes still excluded.
assert "chat" not in pi.REAPABLE_PURPOSES
# ---------------------------------------------------------------------------
# Spawner liveness gate
# ---------------------------------------------------------------------------
def test_live_spawner_protection(ledger, child):
"""A helper whose spawner (this process) lives is never reap-eligible."""
pi.register_child(child.pid, "mcp-helper")
(entry,) = pi.ledger_entries()
assert pi.spawner_is_dead(entry) is False
killed: list[int] = []
reaped = pi.reap_orphaned_mcp_helpers(kill_fn=killed.append)
assert reaped == [] and killed == []
assert psutil.pid_exists(child.pid)
def _orphan_entry_for(child_pid: int) -> None:
"""Rewrite the child's ledger entry so its spawner is a real dead process."""
path = pi._ledger_path()
dead_pid, dead_create = _dead_process_identity()
entries = json.loads(path.read_text(encoding="utf-8"))
for e in entries:
if e["pid"] == child_pid:
e["spawner_pid"] = dead_pid
e["spawner_create"] = dead_create
path.write_text(json.dumps(entries), encoding="utf-8")
def test_dead_spawner_reap_eligibility(ledger, child):
pi.register_child(child.pid, "mcp-helper")
_orphan_entry_for(child.pid)
(entry,) = pi.ledger_entries()
assert pi.spawner_is_dead(entry) is True
killed: list[int] = []
assert pi.reap_orphaned_mcp_helpers(kill_fn=killed.append) == [child.pid]
assert killed == [child.pid]
def test_reap_selection_mixes_live_and_dead_spawners(ledger):
"""Only the orphan is selected; the live-spawner helper is untouched."""
live_proc = subprocess.Popen(["sleep", "300"])
orphan_proc = subprocess.Popen(["sleep", "300"])
try:
pi.register_child(live_proc.pid, "mcp-helper")
pi.register_child(orphan_proc.pid, "mcp-helper")
_orphan_entry_for(orphan_proc.pid)
killed: list[int] = []
reaped = pi.reap_orphaned_mcp_helpers(kill_fn=killed.append)
assert reaped == [orphan_proc.pid]
assert live_proc.pid not in killed
finally:
for p in (live_proc, orphan_proc):
p.kill()
p.wait()
def test_reap_actually_kills_orphan(ledger, child):
"""Default kill path really terminates the orphaned helper."""
pi.register_child(child.pid, "mcp-helper")
_orphan_entry_for(child.pid)
assert pi.reap_orphaned_mcp_helpers() == [child.pid]
deadline = time.time() + 5
while time.time() < deadline and child.poll() is None:
time.sleep(0.05)
assert child.poll() is not None
def test_reap_ignores_non_mcp_purposes(ledger, child):
pi.register_child(child.pid, "serve-child-not-helper")
_orphan_entry_for(child.pid)
assert pi.reap_orphaned_mcp_helpers() == []
assert psutil.pid_exists(child.pid)
# ---------------------------------------------------------------------------
# Updater rung (_ledger_reapable_backend_pids) flow-through
# ---------------------------------------------------------------------------
def test_updater_ledger_rung_flows_mcp_helper(ledger, child):
from hermes_cli import update_cmd
pi.register_child(child.pid, "mcp-helper")
matches = [(child.pid, "python", "sleep 300")]
# Live spawner (this process) → never selected.
assert update_cmd._ledger_reapable_backend_pids(matches) == []
# Provably dead spawner → positively identified as reapable.
_orphan_entry_for(child.pid)
assert update_cmd._ledger_reapable_backend_pids(matches) == [child.pid]
# ---------------------------------------------------------------------------
# Prune-on-write of exited children
# ---------------------------------------------------------------------------
def test_ledger_prunes_exited_children_on_next_write(ledger):
doomed = subprocess.Popen(["sleep", "300"])
pi.register_child(doomed.pid, "mcp-helper")
doomed.kill()
doomed.wait()
deadline = time.time() + 5
while time.time() < deadline and psutil.pid_exists(doomed.pid):
time.sleep(0.05)
survivor = subprocess.Popen(["sleep", "300"])
try:
pi.register_child(survivor.pid, "mcp-helper")
entries = json.loads(ledger.read_text(encoding="utf-8"))
pids = [e["pid"] for e in entries]
assert survivor.pid in pids
assert doomed.pid not in pids
finally:
survivor.kill()
survivor.wait()