in_unix plugin does not work with --under-supervisor (permission denied with var/run/fluent/fluent.sock)

[sijin-won]

Describe the bug

We run fluentd without any the command line option(automatically with --under-supervisor). the in_unix plugin didn't work because the socket file's permission was insufficient.

$ ls -l /var/run/fluent/fluent.sock
srwxr-xr-x 1 _fluentd _fluentd 0 Oct 26 08:27 /var/run/fluent/fluent.sock

To Reproduce

1. Install fluent with the following command

   # fluent-package 5 (LTS)
   curl -fsSL https://toolbelt.treasuredata.com/sh/install-ubuntu-jammy-fluent-package5-lts.sh | sh

2. add configuration

   <source>
   @type unix
   path /var/run/fluent/fluent.sock
   </source>

3. restart fluentd with the following command

   $ sudo systemctl restart fluentd.service

4. The created /var/run/fluent/fluent.sock file can not be written

   $ ls -l /var/run/fluent/fluent.sock
   srwxr-xr-x 1 _fluentd _fluentd 0 Oct 26 08:27 /var/run/fluent/fluent.sock

Expected behavior

The permission should be srwxrwxrwx.

Your Environment

- Fluentd version:

$ sudo fluent-gem list | grep fluentd
fluentd (1.16.2)

• TD Agent version:

• Operating system:

  $ cat /etc/os-release
  PRETTY_NAME="Ubuntu 22.04.3 LTS"
  NAME="Ubuntu"
  VERSION_ID="22.04"
  VERSION="22.04.3 LTS (Jammy Jellyfish)"
  VERSION_CODENAME=jammy
  ID=ubuntu
  ID_LIKE=debian
  HOME_URL="https://www.ubuntu.com/"
  SUPPORT_URL="https://help.ubuntu.com/"
  BUG_REPORT_URL="https://bugs.launchpad.net/ubuntu/"
  PRIVACY_POLICY_URL="https://www.ubuntu.com/legal/terms-and-policies/privacy-policy"
  UBUNTU_CODENAME=jammy

• Kernel version:

  $ uname -r
  6.2.0-1017-gcp

Your Configuration

<source>
  @type unix
  path /var/run/fluent/fluent.sock
</source>

Your Error Log

nothing

Additional context

No response

[ashie]

Expected behavior

The permission should be srwxrwxrwx.

Hmm, it should be customizable.