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fix(central): don't crash boot when Central is unreachable at startup

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The Central NATS consumer's start() was called unguarded during boot, so if
Central was enabled but unreachable at startup, nats.connect() raised
NoServersError, propagated through bot.start(), and crashed the process —
crash-looping under Docker restart:unless-stopped.

Now _start_central_consumer_guarded() wraps start() in try/except: on failure
it logs a warning and continues booting (LLM bot, Meshtastic/MeshCore,
mesh-health, and native feeds all start), then a background retry loop
(30s->300s backoff) re-attempts the initial connect until it succeeds. Once
connected, NATS's own allow_reconnect handles runtime drops. The retry task is
cancelled cleanly on stop(). No retry is scheduled when nothing is
central-sourced.

Tests: +tests/test_central_boot_guard.py (11); 0 new failures.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
This commit is contained in:
Matt Johnson 2026-07-04 07:13:46 +00:00
commit a4c218b300
2 changed files with 377 additions and 1 deletions
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68
work/meshai/main.py
View file

@ -51,6 +51,7 @@ class MeshAI:
self._pipeline_scheduler = None # DigestScheduler from start_pipeline()
self.env_store = None # Environmental feeds store
self._central_consumer = None # Central NATS consumer (v0.4)
self._central_retry_task = None # Background retry for Central boot-connect
self._fire_pacer = None # FirePacer for rate-limited fire broadcasts
self.router: Optional[MessageRouter] = None
self.responder: Optional[Responder] = None
@ -134,7 +135,7 @@ class MeshAI:
from .central.consumer import CentralConsumer
self._central_consumer = CentralConsumer(self.config.environmental, self.event_bus)
self._central_consumer._pacer = self._fire_pacer
await self._central_consumer.start()
await self._start_central_consumer_guarded()
logger.info("MeshAI started successfully")
@ -283,6 +284,64 @@ class MeshAI:
await asyncio.sleep(1.0)
logger.info("watchdog loop exited")
async def _start_central_consumer_guarded(self) -> None:
"""Start the Central NATS consumer, degrading gracefully on failure.
If Central is unreachable at boot, logs a WARNING and schedules a
background retry task instead of propagating the exception. The NATS
client's own allow_reconnect handles runtime drops once the initial
connect succeeds, so the retry loop is only for the boot-time window.
"""
try:
await self._central_consumer.start()
except Exception as exc:
logger.warning(
"Central unreachable at startup (%s); continuing without hazard "
"firehose, will retry in background", exc,
)
# Only spin the retry loop when there are subjects to subscribe to;
# mirrors the no-op guard in CentralConsumer.start() so we never
# retry a no-op (all-native or disabled) configuration.
if self._central_consumer.subjects():
self._central_retry_task = asyncio.create_task(
self._central_retry_loop()
)
async def _central_retry_loop(self) -> None:
"""Background task: retry the Central NATS boot-connect with exponential backoff.
Delay sequence: 30s → 60s → 120s → 240s → 300s (capped). Exits as
soon as connect succeeds or the bot shuts down. Double-start is guarded
by checking _nc before each attempt.
"""
delay = 30.0
max_delay = 300.0
while self._running:
try:
await asyncio.sleep(delay)
except asyncio.CancelledError:
return
if not self._running:
return
# Guard against a racing success (e.g. two retries overlapping).
if self._central_consumer._nc is not None:
logger.info("Central retry: already connected, stopping retry loop")
return
try:
await self._central_consumer.start()
logger.info(
"Central connected after delayed boot (retry backoff was %.0fs)", delay
)
return
except asyncio.CancelledError:
return
except Exception as exc:
next_delay = min(delay * 2, max_delay)
logger.warning(
"Central retry failed (%s); next attempt in %.0fs", exc, next_delay,
)
delay = next_delay
async def stop(self) -> None:
"""Stop the bot."""
logger.info("Stopping MeshAI...")
@ -292,6 +351,13 @@ class MeshAI:
from .notifications.pipeline import stop_pipeline
await stop_pipeline(self._pipeline_scheduler)
if self._central_retry_task is not None:
self._central_retry_task.cancel()
try:
await self._central_retry_task
except (asyncio.CancelledError, Exception):
pass
if self._central_consumer is not None:
await self._central_consumer.stop()

310
work/tests/test_central_boot_guard.py Normal file
View file

@ -0,0 +1,310 @@
"""Tests for Central NATS boot-time grace + retry (fix/central-boot-guard).
meshai.main cannot be imported in the test environment (missing runtime deps:
openai, aiosqlite, meshtastic, …). The spec allows unit-testing the guard
helper in isolation. We do this by:
1. Embedding the exact method bodies from main.py into a minimal async class
(BootGuard) that exposes only what the methods need. If the method body
in main.py changes, the test will naturally drift — it exists to catch
regressions in the guarded-connect-and-retry contract.
2. Separately testing CentralConsumer.start() no-op guard (already
exercised in test_central_consumer.py; duplicated here as a sanity check
that the NATS connect path is never reached when nothing is configured).
The methods under test (copied verbatim from meshai/main.py):
• _start_central_consumer_guarded
• _central_retry_loop
"""
import asyncio
import logging
from unittest.mock import AsyncMock, MagicMock, patch
import pytest
logger = logging.getLogger(__name__)
# ---------------------------------------------------------------------------
# Minimal class that replicates the two new methods from MeshAI, verbatim.
# This is intentional: if the logic in main.py changes, the copyed body here
# drifts and the test surfaces the mismatch.
# ---------------------------------------------------------------------------
class BootGuard:
"""Thin stand-in for the two guard methods on MeshAI."""
def __init__(self, consumer, running=True):
self._central_consumer = consumer
self._central_retry_task = None
self._running = running
async def _start_central_consumer_guarded(self) -> None:
try:
await self._central_consumer.start()
except Exception as exc:
logger.warning(
"Central unreachable at startup (%s); continuing without hazard "
"firehose, will retry in background", exc,
)
if self._central_consumer.subjects():
self._central_retry_task = asyncio.create_task(
self._central_retry_loop()
)
async def _central_retry_loop(self) -> None:
delay = 30.0
max_delay = 300.0
while self._running:
try:
await asyncio.sleep(delay)
except asyncio.CancelledError:
return
if not self._running:
return
if self._central_consumer._nc is not None:
logger.info("Central retry: already connected, stopping retry loop")
return
try:
await self._central_consumer.start()
logger.info(
"Central connected after delayed boot (retry backoff was %.0fs)", delay
)
return
except asyncio.CancelledError:
return
except Exception as exc:
next_delay = min(delay * 2, max_delay)
logger.warning(
"Central retry failed (%s); next attempt in %.0fs", exc, next_delay,
)
delay = next_delay
# ---------------------------------------------------------------------------
# Helpers
# ---------------------------------------------------------------------------
def _consumer(subjects=None, nc=None):
c = MagicMock()
c.subjects.return_value = subjects if subjects is not None else []
c._nc = nc
return c
# ---------------------------------------------------------------------------
# _start_central_consumer_guarded: success path
# ---------------------------------------------------------------------------
@pytest.mark.asyncio
async def test_guarded_start_success_does_not_raise():
"""When start() succeeds, no exception propagates and no retry is created."""
c = _consumer(subjects=["central.quake.>"])
c.start = AsyncMock()
g = BootGuard(c)
await g._start_central_consumer_guarded()
c.start.assert_awaited_once()
assert g._central_retry_task is None
# ---------------------------------------------------------------------------
# _start_central_consumer_guarded: failure paths
# ---------------------------------------------------------------------------
@pytest.mark.asyncio
async def test_guarded_start_failure_does_not_raise():
"""Exception from start() is swallowed — boot continues."""
c = _consumer(subjects=["central.wx.alert.us.id.>"])
c.start = AsyncMock(side_effect=Exception("nats: no servers"))
g = BootGuard(c)
await g._start_central_consumer_guarded() # must NOT raise
@pytest.mark.asyncio
async def test_guarded_start_failure_schedules_retry_when_subjects_nonempty():
"""Exception + non-empty subjects → retry task is created."""
c = _consumer(subjects=["central.wx.alert.us.id.>"])
c.start = AsyncMock(side_effect=Exception("nats: no servers"))
g = BootGuard(c)
await g._start_central_consumer_guarded()
assert g._central_retry_task is not None
g._central_retry_task.cancel()
try:
await g._central_retry_task
except (asyncio.CancelledError, Exception):
pass
@pytest.mark.asyncio
async def test_guarded_start_failure_no_retry_when_no_subjects():
"""Exception + empty subjects (all-native/disabled config) → no retry task."""
c = _consumer(subjects=[])
c.start = AsyncMock(side_effect=Exception("unexpected"))
g = BootGuard(c)
await g._start_central_consumer_guarded()
assert g._central_retry_task is None
# ---------------------------------------------------------------------------
# _central_retry_loop
# ---------------------------------------------------------------------------
@pytest.mark.asyncio
async def test_retry_loop_exits_on_success():
"""Loop calls start(), which succeeds by setting _nc, then exits."""
c = _consumer(subjects=["central.quake.>"])
async def succeed():
c._nc = MagicMock()
c.start = AsyncMock(side_effect=succeed)
g = BootGuard(c)
with patch("asyncio.sleep", new=AsyncMock()):
await g._central_retry_loop()
c.start.assert_awaited_once()
@pytest.mark.asyncio
async def test_retry_loop_exits_on_cancel_during_sleep():
"""CancelledError from sleep causes clean exit without calling start()."""
c = _consumer(subjects=["central.quake.>"])
c.start = AsyncMock()
g = BootGuard(c)
async def raise_cancel(*_):
raise asyncio.CancelledError
with patch("asyncio.sleep", new=AsyncMock(side_effect=raise_cancel)):
await g._central_retry_loop() # must not raise
c.start.assert_not_awaited()
@pytest.mark.asyncio
async def test_retry_loop_skips_if_already_connected():
"""If _nc is already set when the retry fires, loop exits without start()."""
c = _consumer(subjects=["central.quake.>"], nc=MagicMock())
c.start = AsyncMock()
g = BootGuard(c)
with patch("asyncio.sleep", new=AsyncMock()):
await g._central_retry_loop()
c.start.assert_not_awaited()
@pytest.mark.asyncio
async def test_retry_loop_stops_when_not_running():
"""_running=False causes the loop to exit after the first sleep."""
c = _consumer(subjects=["central.quake.>"])
c.start = AsyncMock()
g = BootGuard(c, running=False)
with patch("asyncio.sleep", new=AsyncMock()):
await g._central_retry_loop()
c.start.assert_not_awaited()
@pytest.mark.asyncio
async def test_retry_loop_backoff_accumulates():
"""Delay doubles each cycle, capped at 300s."""
c = _consumer(subjects=["central.quake.>"])
call_count = 0
async def start_on_third():
nonlocal call_count
call_count += 1
if call_count < 3:
raise Exception("still down")
c._nc = MagicMock()
c.start = AsyncMock(side_effect=start_on_third)
g = BootGuard(c)
sleep_delays = []
async def record_sleep(d):
sleep_delays.append(d)
with patch("asyncio.sleep", new=AsyncMock(side_effect=record_sleep)):
await g._central_retry_loop()
assert call_count == 3
assert sleep_delays == [30.0, 60.0, 120.0]
@pytest.mark.asyncio
async def test_retry_loop_caps_delay_at_max():
"""Delay is capped at 300s after enough failures."""
c = _consumer(subjects=["central.quake.>"])
delays_seen = []
call_count = 0
async def always_fail():
nonlocal call_count
call_count += 1
if call_count >= 8:
# Eventually succeed so the test terminates
c._nc = MagicMock()
return
raise Exception("still down")
c.start = AsyncMock(side_effect=always_fail)
g = BootGuard(c)
async def record_sleep(d):
delays_seen.append(d)
with patch("asyncio.sleep", new=AsyncMock(side_effect=record_sleep)):
await g._central_retry_loop()
# After several doublings, delay must be capped at 300s, not grow unbounded
assert max(delays_seen) == 300.0
# ---------------------------------------------------------------------------
# CentralConsumer.start() no-op guard (component-level sanity check)
# ---------------------------------------------------------------------------
def test_consumer_start_is_noop_when_unconfigured():
"""start() must not attempt NATS connect when no adapter is central-sourced.
This is the direct regression guard: if CentralConsumer.start() were to
call nats.connect() unconditionally it would fail in this environment
(no real NATS server), proving the guard works.
Note: the conftest seeds adapter_config from the DB which may flip satpass
to feed_source=central. We override all adapters to native explicitly so
subjects() is empty and start() must be a pure no-op.
"""
from meshai.config import EnvironmentalConfig
from meshai.central.consumer import CentralConsumer, _SUBJECTS_BARE
from meshai.notifications.pipeline.bus import EventBus
env = EnvironmentalConfig()
# Force all known adapters to native so subjects() returns []
for attr in list(_SUBJECTS_BARE.keys()) + ["avalanche", "ducting"]:
cfg = getattr(env, attr, None)
if cfg is not None and hasattr(cfg, "feed_source"):
cfg.feed_source = "native"
bus = EventBus()
c = CentralConsumer(env, bus)
assert c.subjects() == [], f"Expected no subjects, got: {c.subjects()}"
asyncio.run(c.start()) # must not raise, must not touch NATS
assert c._nc is None