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FabledSteward/plugins/host_agent/__init__.py
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bvandeusenandClaude Opus 5.5 b6c4ce510d
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fix(host_agent): a stalled NFS mount no longer freezes the agent (#5760)
#5760 "One stalled NFS mount freezes the whole agent: statvfs has no
deadline, so the host goes silent while it still answers ping". The agent
read every mount inline in its only loop; a hard-mounted share whose server
stops blocks statvfs in the kernel with no timeout. Each mount is now read
in a daemon thread under one 5 s deadline. One that misses it is sent as
stalled, and isn't probed again while its last probe is still blocked. A
mount that errors (a stale handle) is left out instead of emptying the list.

Steward counts them as mounts_stalled (alertable: "an NFS share stopped"),
and skips the fullest-disk figure when every mount stalled.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
2026-10-14 17:12:27 -04:00

75 lines
3.2 KiB
Python

# plugins/host_agent/__init__.py
from __future__ import annotations
from typing import TYPE_CHECKING
if TYPE_CHECKING:
from quart import Quart
_app: "Quart | None" = None
def setup(app: "Quart") -> None:
global _app
_app = app
# A host's CPU, memory and load per core learn their normal (#5742), each
# with its floor from Settings → Thresholds. Parts don't: a host's CPU has
# a normal, each of its cores doesn't. Disks stay on their fixed cutoffs:
# a nearly full disk is a failure whatever its history (System 182).
from steward.core.norms import floor_setting, learn_normal
learn_normal("host_agent", "cpu_pct", floor_setting(app, "host_cpu_pct"), parts=False)
learn_normal("host_agent", "mem_used_pct", floor_setting(app, "host_mem_pct"), parts=False)
learn_normal("host_agent", "load_pct", floor_setting(app, "host_load_pct"), parts=False)
# "Agent offline" speaks for everything the agent carries: while it is
# firing, the host's other rules going silent isn't emailed (#5721).
from steward.core.alerts import agent_fed, agent_heartbeat
from steward.hosts.service import agent_stale_after_seconds
agent_heartbeat("host_agent", "seconds_since_seen", lambda: agent_stale_after_seconds(app.config))
agent_fed("host_agent", lambda resource: resource.split(":", 1)[0])
# A reboot the agent announced is silence with a reason, for a while (#5756).
from datetime import datetime, timezone
from steward.core.alerts import agents_away
from .downtime import hosts_away, restart_grace_seconds
agents_away(lambda session: hosts_away(session, datetime.now(timezone.utc),
restart_grace_seconds(app.config)))
from steward.core.cleanup import prune_by_age
from .models import HostDowntime
prune_by_age(HostDowntime.started_at)
def get_scheduled_tasks() -> list:
from .scheduler import make_task
return [make_task(_app)]
def get_blueprint():
from .routes import host_agent_bp
return host_agent_bp
def register_mcp_tools(register) -> None:
from .mcp_tools import register_tools
register_tools(register)
async def mcp_overview(db) -> list[dict]:
from .mcp_tools import mcp_overview as findings
return await findings(db)
def get_alert_metrics() -> dict[str, list[str]]:
"""Host metrics ingest records for alert rules (resource = the host name;
disk_used_pct per mount, resource "<host>:<mount>"). seconds_since_seen
comes from the scheduler, not the agent: "agent offline" is > 180.
clock_off_secs is how far the host's clock is from Steward's, either way
(agent ≥ 1.12.0): "clock drifting" is > 30. load_pct is load_1m as a %
of the host's cores. inodes_used_pct is per mount (agent ≥ 1.13.0), and
disk_used_pct_worst is the fullest mount by space or inodes.
mounts_stalled counts the mounts that didn't answer the agent in time
(agent ≥ 1.14.0): "an NFS share stopped" is > 0."""
return {"host_agent": [
"cpu_pct", "mem_used_pct", "mem_available_bytes", "swap_used_bytes",
"disk_used_pct_worst", "disk_used_pct", "inodes_used_pct", "load_1m", "load_5m", "load_15m",
"load_pct",
"uptime_secs", "seconds_since_seen", "clock_off_secs", "mounts_stalled",
]}