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Fix: Gracefully handle exceptions in PubSub message retrieval #625

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merged 1 commit into from
Sep 30, 2025
+24 −4
Merged

Fix: Gracefully handle exceptions in PubSub message retrieval #625

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28 changes: 24 additions & 4 deletions api/pubsub.py
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Original file line number Diff line number Diff line change
Expand Up @@ -5,6 +5,7 @@

"""Pub/Sub implementation"""

import logging
import asyncio

import json
Expand All @@ -14,6 +15,8 @@
from .models import Subscription, SubscriptionStats
from .config import PubSubSettings

logger = logging.getLogger(__name__)


class PubSub:
"""Pub/Sub implementation class
Expand All @@ -39,7 +42,9 @@ def __init__(self, host=None, db_number=None):
host = self._settings.redis_host
if db_number is None:
db_number = self._settings.redis_db_number
self._redis = aioredis.from_url(f'redis://{host}/{db_number}')
self._redis = aioredis.from_url(
f'redis://{host}/{db_number}', health_check_interval=30
)
# self._subscriptions is a dict that matches a subscription id
# (key) with a Subscription object ('sub') and a redis
# PubSub object ('redis_sub'). For instance:
Expand Down Expand Up @@ -135,9 +140,24 @@ async def listen(self, sub_id, user=None):
f"not owned by {user}")
while True:
self._subscriptions[sub_id]['last_poll'] = datetime.utcnow()
msg = await sub['redis_sub'].get_message(
ignore_subscribe_messages=True, timeout=1.0
)
msg = None
try:
msg = await sub['redis_sub'].get_message(
ignore_subscribe_messages=True, timeout=1.0
)
except aioredis.ConnectionError:
async with self._lock:
channel = self._subscriptions[sub_id]['sub'].channel
new_redis_sub = self._redis.pubsub()
await new_redis_sub.subscribe(channel)
self._subscriptions[sub_id]['redis_sub'] = new_redis_sub
sub['redis_sub'] = new_redis_sub
Comment on lines +148 to +154
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Here the method creates a new subscription on connection error. How will the client receive the new sub ID?
The client will need it to keep listening and also to unsubscribe.
I think it's better to return None instead of creating a new subscription.
The client will need to subscribe again in this case.

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We’re not creating a new subscription ID here—only a new redis_sub object bound to the same sub_id.

On ConnectionError we resubscribe to the same channel and update self._subscriptions[sub_id]['redis_sub'], so the client keeps using the original sub_id for both listening and unsubscribe(). No new ID is generated or needed.
As i recall subscription id we generate artificially in python using counter in redis named kernelci-api-pubsub-id (ID_KEY). Redis Pub/Sub has no subscription IDs or message IDs.

continue
except aioredis.RedisError as exc:
# log the error and continue
logger.error("Redis error occurred: %s", exc)
return None # Handle any exceptions gracefully
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I'd suggest to log something before returning None just to know afterwards what happened from the logs.

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Done


if msg is None:
continue
msg_data = json.loads(msg['data'])
Expand Down