Checklist

• I have verified that the issue exists against the master branch of Celery.
• I have read the relevant section in the
  contribution guide
  on reporting bugs.
• I have checked the issues list
  for similar or identical bug reports.
• I have checked the pull requests list
  for existing proposed fixes.
• I have checked the commit log
  to find out if the bug was already fixed in the master branch.
• I have included all related issues and possible duplicate issues
  in this issue (If there are none, check this box anyway).

Mandatory Debugging Information

• I have included the output of celery -A proj report in the issue.
  (if you are not able to do this, then at least specify the Celery
  version affected).
• I have verified that the issue exists against the master branch of Celery.
• I have included the contents of pip freeze in the issue.
• I have included all the versions of all the external dependencies required
  to reproduce this bug.

Optional Debugging Information

• I have tried reproducing the issue on more than one Python version
  and/or implementation.
• I have tried reproducing the issue on more than one message broker and/or
  result backend.
• I have tried reproducing the issue on more than one version of the message
  broker and/or result backend.
• I have tried reproducing the issue on more than one operating system.
• I have tried reproducing the issue on more than one workers pool.
• I have tried reproducing the issue with autoscaling, retries,
  ETA/Countdown & rate limits disabled.
• I have tried reproducing the issue after downgrading
  and/or upgrading Celery and its dependencies.

Related Issues and Possible Duplicates

Related Issues

• None

Possible Duplicates

• None

Environment & Settings

Celery version:

software -> celery:5.0.1 (singularity) kombu:5.0.2 py:3.8.3
            billiard:3.6.3.0 redis:3.5.3
platform -> system:Linux arch:64bit, ELF
            kernel version:5.4.0-48-generic imp:CPython
loader   -> celery.loaders.app.AppLoader
settings -> transport:redis results:disabled

Steps to Reproduce

Required Dependencies

• Minimal Python Version: N/A or Unknown
• Minimal Celery Version: 5.0.1
• Minimal Kombu Version: N/A or Unknown
• Minimal Broker Version: N/A or Unknown
• Minimal Result Backend Version: N/A or Unknown
• Minimal OS and/or Kernel Version: N/A or Unknown
• Minimal Broker Client Version: N/A or Unknown
• Minimal Result Backend Client Version: N/A or Unknown

Python Packages

Other Dependencies

Minimally Reproducible Test Case

$ celery multi start normal low --app=service.celery:app --logfile=/tmp/celery/celery-%n%I.log --queues:normal=normal --queues:low=low --concurrency:normal=2 --concurrency:low=1 --pidfile=/tmp/celery/celeryd-%n.pid
celery multi v5.0.1 (singularity)
> Starting nodes...
	> normal@dell: OK
	> low@dell: OK

Expected Behavior

Celery 4.4.7 behavior

$ ls -l /tmp/celery
-rw-r--r-- 1 www-data www-data   6 Oct 19 14:39 celeryd-low.pid
-rw-r--r-- 1 www-data www-data   6 Oct 19 14:39 celeryd-normal.pid
-rw-rw-r-- 1 www-data www-data  80 Oct 19 14:39 celery-low-1.log
-rw-rw-r-- 1 www-data www-data 316 Oct 19 14:39 celery-low.log
-rw-rw-r-- 1 www-data www-data  80 Oct 19 14:39 celery-normal-1.log
-rw-rw-r-- 1 www-data www-data  80 Oct 19 14:39 celery-normal-2.log
-rw-rw-r-- 1 www-data www-data 316 Oct 19 14:39 celery-normal.log

Actual Behavior

$ ls -l /tmp/celery
-rw-r--r-- 1 www-data www-data   6 Oct 19 14:39 celeryd-low.pid
-rw-r--r-- 1 www-data www-data   6 Oct 19 14:39 celeryd-normal.pid
-rw-rw-r-- 1 www-data www-data  80 Oct 19 14:39 celery-low-1.log
-rw-rw-r-- 1 www-data www-data   0 Oct 19 14:39 celery-low%I.log
-rw-rw-r-- 1 www-data www-data 316 Oct 19 14:39 celery-low.log
-rw-rw-r-- 1 www-data www-data  80 Oct 19 14:39 celery-normal-1.log
-rw-rw-r-- 1 www-data www-data  80 Oct 19 14:39 celery-normal-2.log
-rw-rw-r-- 1 www-data www-data   0 Oct 19 14:39 celery-normal%I.log
-rw-rw-r-- 1 www-data www-data 316 Oct 19 14:39 celery-normal.log