[Python] Flask inside docker consuming disk space by itselt, while idle

I have a very simple flask api inside of docker container, based on python:3.12. Currently, it has a couple of endpoints that make requests to a postgres db (another container) and return json results. No caching, no writing to disk whatsoever. DB engine is psycopg2. requirements.txt is minimal as well (see below). Requests are made via nginx reverse proxy (another container).

If I go into the container and run df -m, then I can see that free disk space is decreasing ~500m/min. If I run du -sh /* to see directory sizes in /, they seem normal and not changing over time. This happens until space completely exhausted, I have to re-create container and it repeats again. This happens even if no requests are made.

How to debug it? I'm lost.

Here's some additional info:

Dockerfile

FROM python:3.12

WORKDIR /app

COPY requirements.txt .
RUN pip install --no-cache-dir -r requirements.txt

COPY . .

CMD ["python", "app.py"]


docker-compose service:

api_v1:
container_name: bagg_api
shm_size: 512m
build:
context: ./api
dockerfile: Dockerfile
# ports:
# - "5005:5000"
networks:
- b_agg-network
env_file:
- dev.env
depends_on:
- postgres
restart: unless-stopped
volumes:
- ./api:/app
- ./scripts:/scripts
- ./week-data:/week-data
- ./logs/api:/var/log


requirements.txt

Flask
psycopg2-binary
pyyaml
pandas


Terminal output (space already nearly exhausted, 60 gig!)

root@1cf4d41fc2fe:/app# date; df -m; date
Thu May 29 17:50:11 PDT 2025
Filesystem 1M-blocks Used Available Use% Mounted on
overlay 59768 55604 1097 99% /
tmpfs 64 0 64 0% /dev
shm 512 1 512 1% /dev/shm
/run/host_mark/Users 1902789 1748624 154165 92% /app
/dev/vda1 59768 55604 1097 99% /etc/hosts
tmpfs 3919 0 3919 0% /proc/scsi
tmpfs 3919 0 3919 0% /sys/firmware
Thu May 29 17:50:11 PDT 2025
root@1cf4d41fc2fe:/app# ps -aux
USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND
root 1 0.0 1.0 540416 83884 ? Ssl 17:32 0:01 python app.py
root 16 0.2 1.0 614228 84080 ? Sl 17:32 0:02 /usr/local/bin/python app.py
root 46 0.0 0.0 4476 3416 pts/0 Ss 17:48 0:00 bash
root 66 0.0 0.0 8588 4048 pts/0 R+ 17:50 0:00 ps -aux
root@1cf4d41fc2fe:/app# du -sh /*
16K /app [mounted from host]
0 /bin
4.0K /boot
0 /dev
2.1M /etc
4.0K /home
0 /lib
4.0K /media
4.0K /mnt
4.0K /opt
du: cannot access '/proc/67/task/67/fd/3': No such file or directory
du: cannot access '/proc/67/task/67/fdinfo/3': No such file or directory
du: cannot access '/proc/67/fd/3': No such file or directory
du: cannot access '/proc/67/fdinfo/3': No such file or directory
0 /proc
28K /root
8.0K /run
0 /sbin
2.2M /scripts [mounted from host]
4.0K /srv
0 /sys
4.0K /tmp
1.2G /usr
15M /var
122G /week-data [mounted from host]


/var/log is also mounted, and is empty

I also tried python:3.12-slim, same outcome.

I don't want to attach app.py, but there's nothing that writes to disk, also I want to find out where the space goes, for starter.

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