Table empty or key no longer exists

[sreedharbukya]

The issue with redis key getting evicted every time. I read an old issue link. I have confirmed that my Redis instance is not hacked. In fact, we are using Secured Redis.

OperationalError("\nCannot route message for exchange 'reply.celery.pidbox': Table empty or key no longer exists.\nProbably the key ('_kombu.binding.reply.celery.pidbox') has been removed from the Redis database.\n",)

kombu==4.5.0
celery==4.3.0
redis==3.2.1

Is this some issue with redis?

[tbolis]

same issue here, is there any workaround on this? celery workers will freeze after that and we need a restart

[thedrow]

This can happen if you set Redis to LRU mode or something similar.
Please configure Redis correctly and increase the memory of your Redis instance.

Feel free to comment if you find this is still an issue with Kombu.

[ra-coder]

what you mean by 'configure Redis correctly' ?

I have same problem in flask app with next config.py

# redis
REDIS_URL = os.environ['REDIS_URL']

# flask-caching
CACHE_TYPE = 'redis'
CACHE_KEY_PREFIX = 'glue_flask_cache_'
CACHE_REDIS_URL = REDIS_URL

[thedrow]

Check your redis.conf.
Specifically maxmemory-policy.
If its set to noeviction or does not have a value we may have a problem in Celery.

[danleyb2]

faced this same issue on the first queue whenever i started a second or more queues

fixed by downgrading kombu==4.5.0 from kombu==4.6.5

had nothing to do with redis. just the missing key _kombu.binding.reply.celery.pidbox that is never created if you redis-cli monitor

[LuRsT]

I found the same issue, @danleyb2, did you figure out what the problem was with the current version?

Update: Downgrading to v4.5.0 solved the issue. Thanks @danleyb2

[auvipy]

This is present in celery integration Redis tests as well!

[LuRsT]

I noticed @auvipy, any plans on fixing it? Do you need any help?

[auvipy]

yes if you have time!

[StingyJack]

I was having this problem with kombu 4.5.0 when using celery as a service in a docker-compose pod that included a redis server image and a few app images. When I used up -d <serviceName> and started services individually, starting with Redis, the error would show up in the logs repeatedly. when I used up -d without a service name, this problem seemed to go away.

Edit: the version I named is likely incorrect. Our project's setup.py record was missing a comma between version ranges so it was using or applying whatever version was above the concatenation of the min and max versions. Which would have been the affected package version at some times.

[killthekitten]

Looks like the reason is #1087. The bug showed up last week, after 4.6.4 -> 4.6.5 migration.

[killthekitten]

@auvipy could you point to the failing integration test, please? I couldn't reproduce the bug locally, so I just pinned the version to 4.6.4 blindly.

[boomxy]

Looks like the reason is #1087. The bug showed up last week, after 4.6.4 -> 4.6.5 migration.

thanks you, 4.6.4 it works!

[jorijinnall]

Had the same issue.
I fixed by downgrading kombu from 4.6.5 to 4.6.3
I still had the bug in version 4.6.4

[travishen]

same issue here

celery==4.3.0
redis==3.2.1
kombu==4.6.3  # downgrade meant for an flower issue https://github.com/mher/flower/issues/909

I found the error start to occur at worker recreate (e.g. k8s pod scaling), and affect to all the other workers.
The worker has additional settings: concurrency(prefork) and max-memory -per-child

[kravietz]

kombu==4.6.3 fixed it for me -- had the same issue with Celery worker crashing.

[auvipy]

what about kombu==4.6.4?

[Dogrtt]

... multiple workers ...

I've got one Docker container with single Celery worker in --pool=solo mode on aboard. I faced the same issue several minutes ago. Celery 5.1.2, Kombu 5.1.0. I used redis-cli ping for healthcheck but I removed it in last MR, will check if issue still here and write back.

[matusvalo]

I've got one Docker container with single Celery worker in --pool=solo mode on aboard. I faced the same issue several minutes ago.

Hmm I tried the example above with single worker and I was not able to reproduce the issue even with unpatched kombu:

celery -A tasks worker -E --loglevel=INFO --autoscale=1

[matusvalo]

Potential fix created in PR #1394 . Please test. For now I am marking it as draft. The best is to have multiple users confirming this fix.

[Dogrtt]

Hi @matusvalo, I added your fix to my container's kombu v.5.1.0 manually, but I'm still facing this issue:

kombu.exceptions.OperationalError:
Cannot route message for exchange 'reply.celery.pidbox': Table empty or key no longer exists.
Probably the key ('_kombu.binding.reply.celery.pidbox') has been removed from the Redis database.

Problem is that on my local PC everything is fine, but when I'm running Celery container on VM this issue comes...
So I can't say that the solution is not working, but for some reason it still happening for me.

[matusvalo]

@Dogrtt are you able prepare some reproducable case? If yes please post it here and we will reopen the issue.

[auvipy]

Hi @matusvalo, I added your fix to my container's kombu v.5.1.0 manually, but I'm still facing this issue:

kombu.exceptions.OperationalError:
Cannot route message for exchange 'reply.celery.pidbox': Table empty or key no longer exists.
Probably the key ('_kombu.binding.reply.celery.pidbox') has been removed from the Redis database.

Problem is that on my local PC everything is fine, but when I'm running Celery container on VM this issue comes... So I can't say that the solution is not working, but for some reason it still happening for me.

you should directly use from main branch

[omoumniabdou]

@Dogrtt Same for me.

celery[redis]==4.4.6
kombu==4.6.11
redis==3.5.3 (server 5.0.3)

I patched the app but we still have the issue:

class FixedMailbox(Mailbox):
    """
    Patch kombu 4.6.11 with a PR from kombu 5
    See https://github.com/celery/kombu/pull/1394
    """

    @property
    def oid(self):
        return oid_from(self)


class FixedControl(Control):
    Mailbox = FixedMailbox


app = Celery("pipeline", control=FixedControl)

[adililhan]

@matusvalo Hi, I managed to (accidentally) reproduce this error. I added time.sleep(3) to the ping function: https://github.com/celery/celery/blob/master/celery/worker/control.py#L322

Like this:

@inspect_command(default_timeout=0.2)
def ping(state, **kwargs):
    time.sleep(3)
    return ok('pong')

After that, I tried to send a ping request to the Celery instance:

celery.control.inspect().ping()

I got the same error.

"Control command error: OperationalError(\"\\nCannot route message for exchange 'reply.celery.pidbox': Table empty or key no longer exists.\\nProbably the key ('_kombu.binding.reply.celery.pidbox') has been removed from the Redis database.\\n\")"

So, this error occurs if the ping function doesn't return a response within a reasonable time frame. I hope this sample will help you understand the issue.

[matusvalo]

I can confirm the bug. I have checked it also before #1394 and it is still occurring so it is not introduced by this fix 🎉 . Hence, this bug has different root cause then the bug fixed by #1394. I have checked this bug and it is still occurring when concurrency is set to 1.

[matusvalo]

OK I did investigation and here are results:

1. set keys in Redis works in a way that when you remove the last record from the set key, the set key is removed from redis
2. _kombu.binding.reply.celery.pidbox key in redis is of type set and it contains queues bound to the virtual exchange
3. the celery.control.inspect().ping() method is not synchronous. It means it does not wait for response from Celery workers. If it does not get response "immediately" it returns None.
4. Methodcelery.control.inspect().ping() in the beginning creates new queue and put it to _kombu.binding.reply.celery.pidbox. After executing logic of method, the queue is deleted/removed and hence removed from the set.

Hence, in 99.99% cases we are not able to see anything because the workers are fast enough to write response before celery.control.inspect().ping() returns. But by artificial introduction of delay using sleep() in responding of ping to client we have corner case when the worker respons after method celery.control.inspect().ping() returns. But due 4. the queue does not exists and is removed from the _kombu.binding.reply.celery.pidbox set. Moreover, if it is that queue was the only one present, the set is deleted from redis due 1. in the time when worker tries to write reply to the queue using the virtual exchange. And this is causing the exception we are seeing.

[matusvalo]

So we should unify logic of kombu for cases in Redis transport when

1. the virtual exchange key exists in redis but does not contain the queue and hence we cannot route the message to queue
2. the virtual exchange key does not exists in redis and also we cannot route the message to queue

Or at least we need to change the exception message because it is misleading. Instead of

Cannot route message for exchange 'reply.celery.pidbox': Table empty or key no longer exists.\nProbably the key ('_kombu.binding.reply.celery.pidbox') has been removed from the Redis database.\n

we should have something like

Cannot route message. No queues bound to exchange.

[matusvalo]

PR fixing the issue created. Basically I have just removed the raise of the exception. It seems that it should fix the issue and I consider that the exception does not have any benefit because:

1. table can be removed any time - when publishing against empty exchange
2. the amqp protocol which we simulate by default destroys all unroutable messages
3. currently the message which does not have routing key in table is destroyed when table is not empty

See the integration tests of the PR for details

[matusvalo]

Can someone check and verify the fix #1404 in order to understand whether it fixes issues for you?

[omoumniabdou]

hello @matusvalo
I can confirm that the fix #1404 works for us. We had the issue every few hours on our pipeline (2 servers with dozen of workers each) since we changed our redis server (from version 5.0.1 to 5.0.3):

celery[redis]==4.4.6
kombu==4.6.11
redis==3.5.3 (server 5.0.3)

For those who do not want to upgrade, you can patch kombu.transport.redis :

import kombu.transport.redis
from kombu.exceptions import InconsistencyError
from kombu.transport import TRANSPORT_ALIASES


class FixedChannel(kombu.transport.redis.Channel):
    def get_table(self, exchange):
        try:
            return super().get_table(exchange)
        except InconsistencyError:  # pragma: no cover
            # table does not exists since all queues bound to the exchange
            # were deleted. We need just return empty list.
            return []


class FixedTransport(kombu.transport.redis.Transport):
    Channel = FixedChannel

# Hack to override redis transport impl
TRANSPORT_ALIASES["redis"] = "$PATH_THIS_FILE:FixedTransport"

[lpsinger]

Check your redis.conf.
Specifically maxmemory-policy.
If its set to noeviction or does not have a value we may have a problem in Celery.

We're seeing these errors with kombu 5.2.1 and celery 5.1.2. We do have maxmemory-policy set to volatile-lru. Do we need to change it to noeviction in order to fix this?

[matusvalo]

We're seeing these errors with kombu 5.2.1 and celery 5.1.2.

Which errors do you see? Can you provide the traceback? The whole exception was removed in #1404.

[lpsinger]

We're seeing these errors with kombu 5.2.1 and celery 5.1.2.

Which errors do you see? Can you provide the traceback? The whole exception was removed in #1404.

See https://git.ligo.org/emfollow/gwcelery/-/issues/397.

[matusvalo]

Are you sure that you are using kombu v. 5.2.1? As I said exception below was removed in Kombu 5.2.0. - see #1404.

  File "/home/emfollow-playground/.local/lib/python3.8/site-packages/kombu/transport/redis.py", line 884, in get_table
    raise InconsistencyError(NO_ROUTE_ERROR.format(exchange, key))
kombu.exceptions.InconsistencyError: 
Cannot route message for exchange 'reply.celery.pidbox': Table empty or key no longer exists.
Probably the key ('_kombu.binding.reply.celery.pidbox') has been removed from the Redis database.

[lpsinger]

No, we were using kombu 5.1.0. I just updated.

[matusvalo]

No, we were using kombu 5.1.0. I just updated.

Please update kombu to latest version where the issue is fixed.

[matejruzicka]

hello @matusvalo I can confirm that the fix #1404 works for us. We had the issue every few hours on our pipeline (2 servers with dozen of workers each) since we changed our redis server (from version 5.0.1 to 5.0.3):

celery[redis]==4.4.6 kombu==4.6.11 redis==3.5.3 (server 5.0.3)

For those who do not want to upgrade, you can patch kombu.transport.redis :

import kombu.transport.redis
from kombu.exceptions import InconsistencyError
from kombu.transport import TRANSPORT_ALIASES


class FixedChannel(kombu.transport.redis.Channel):
    def get_table(self, exchange):
        try:
            return super().get_table(exchange)
        except InconsistencyError:  # pragma: no cover
            # table does not exists since all queues bound to the exchange
            # were deleted. We need just return empty list.
            return []


class FixedTransport(kombu.transport.redis.Transport):
    Channel = FixedChannel

# Hack to override redis transport impl
TRANSPORT_ALIASES["redis"] = "$PATH_THIS_FILE:FixedTransport"

I am so sorry but do you think you could advise me on how exactly to use this patch? What file do I add it to? Or do I put it in a new file? Where should the file be located? What should it be called? Should the file be called from somewhere from within the app? Shou this part "$PATH_THIS_FILE:FixedTransport" be replaced for something? What does PATH_THIS_FILE stand for?