symfony 5.3 logfile could not be opened in append mode: Failed to open stream (docker) - docker

Question

I have a rotating Logfile configured with monolog, which worked like a charm and suddenly I get error messages stating that the file cannot be created, when the frontend is calling my symfony backend, which runs in a alpine docker container.
Creating logfiles while running my phpunit tests is causing no trouble at all.
This is my monolog configuration, which didn't change:
monolog:
handlers:
frontend:
type: rotating_file
path: "%kernel.logs_dir%/%kernel.environment%.frontend.log"
level: error
channels: [ frontend ]
max_files: 3
main:
type: rotating_file
path: "%kernel.logs_dir%/%kernel.environment%.log"
level: debug
channels: [ "!event", "!frontend", "!deprecation" ]
max_files: 3
console:
type: console
process_psr_3_messages: false
channels: [ "!event", "!doctrine", "!console", "!frontend", "!deprecation" ]
What I did was disabling sessions, which should have no influence on whether the system is able to create a file for writing.
Why can my server no longer write logfiles?
My permissions for my log folder are increased to 777 and the server runs as "root" in it's container:
e9dffe459185:/var/www/var# ll
total 8
drwxrwxr-x 6 root root 192 Jul 22 15:07 ./
drwxr-xr-x 51 root root 1632 Jul 23 10:16 ../
drwxrwxr-x 4 root root 128 Jul 23 11:01 cache/
drwxrwxrwx 3 root root 96 Jul 23 11:02 log/

Answer 1

Looks like the problem was fixed with an update of monolog:
Updating dependencies
Lock file operations: 0 installs, 1 update, 0 removals
- Upgrading monolog/monolog (2.3.1 => 2.3.2)
Writing lock file
Installing dependencies from lock file (including require-dev)
Package operations: 0 installs, 1 update, 0 removals
- Downloading monolog/monolog (2.3.2)
- Upgrading monolog/monolog (2.3.1 => 2.3.2): Extracting archive
Looks like version 2.3.1 was buggy. Since the upgrade I don't have further problems.