Codeigniter not logging

$config['log_path'] is supposed to be a path to a directory, not a file. CI writes its own files in the format log-2012-12-05.php. Try a path to a directory, and make sure to include a trailing slash.

/*
|--------------------------------------------------------------------------
| Error Logging Directory Path
|--------------------------------------------------------------------------
|
| Leave this BLANK unless you would like to set something other than the default
| application/logs/ folder. Use a full server path with trailing slash.
|
*/
$config['log_path'] = '/var/log/ci_logs/';

the problem is SELinux check this post.

you try this:

# Ownership
sudo chown apache:apache -R /data/www/html/sites/mysite
cd /data/www/html/sites/mysite

# File permissions, recursive
find . -type f -exec chmod 0644 {} \;

# Dir permissions, recursive
find . -type d -exec chmod 0755 {} \;

# SELinux serve files off Apache, resursive
sudo chcon -t httpd_sys_content_t /data/www/html/sites/mysite -R

# Allow write only to specific dirs
sudo chcon -t httpd_sys_rw_content_t /data/www/html/sites/mysite/logs -R
sudo chcon -t httpd_sys_rw_content_t /data/www/html/sites/mysite/uploads -R

https://blog.lysender.com/2015/07/centos-7-selinux-php-apache-cannot-writeaccess-file-no-matter-what/