Unable to diagnose MISCONF redis issue while launching celery worker server - redis

Question

I use a celery worker server with redis as the broker url (for receiving tasks) as well as the result backend.
BROKER_URL = 'redis://localhost:6379/2'
CELERY_RESULT_BACKEND = 'redis://localhost:6379/2'
app = Celery('myceleryapp', broker=BROKER_URL,backend=CELERY_RESULT_BACKEND)
I launch the celery worker server using celery -A myceleryapp worker -l info -c 8
The worker processes start processing my tasks from the redis queue until at some point, I receive the infamous MISCONF redis error and the celery worker process terminates.
Unrecoverable error: ResponseError('MISCONF Redis is configured to save RDB snapshots, but is currently not able to persist on disk. Commands that may modify the data set are disabled. Please check Redis logs for details about the error.',)
I checked the redis log files in /var/log/redis and the tail end of the file has the following
24745:C 19 Aug 09:20:26.169 * RDB: 0 MB of memory used by copy-on-write
1590:M 19 Aug 09:20:26.247 * Background saving terminated with success
1590:M 19 Aug 09:25:27.080 * 10 changes in 300 seconds. Saving...
1590:M 19 Aug 09:25:27.081 * Background saving started by pid 25397
25397:C 19 Aug 09:25:27.082 # Write error saving DB on disk: No space left on device
1590:M 19 Aug 09:25:27.181 # Backgroun1590:M 19 Aug 09:51:03.042 * 1 changes in 900 seconds. Saving...
1590:M 19 Aug 09:51:03.042 * Background saving started by pid 26341
26341:C 19 Aug 09:51:03.405 * DB saved on disk
26341:C 19 Aug 09:51:03.405 * RDB: 22 MB of memory used by copy-on-write
1590:M 19 Aug 09:51:03.487 * Background saving terminated with success
The dump.rdb file is being written to /var/lib/redis/dump.rdb.
Since the logs reported a No space left on device, I checked the disk space where /var is mounted and there seems to be sufficient space left (1.2GB).
How do I get to the root cause of this error if there is enough disk space? Of course, to prevent this error from happening, I could set config set stop-writes-on-bgsave-error no in redis-cli. But I want to get to the root cause of this error. Any help or pointers?

Answer 1

Maybe this is caused by the swap file. Because the swap file took the 1.2Gb space of your disk. So redis complains No space to write.
Try this "swapon -s" command to check this.
I think 1.2Gb is not enough if this disk accept the RAM page swap. you should change the dir of RDB in a more big dir.