keystone.conf [DEFAULT] max_token_size should be adjusted.
This option is intended to protect keystone from unreasonably sized tokens, where “reasonable” is mostly dependent on the keystone.conf [token] provider that you’re using. If you’re using one of the following token providers, then you should set keystone.conf [DEFAULT] max_token_size accordingly:
For Fernet, set keystone.conf [DEFAULT] max_token_size = 255, because Fernet tokens should never exceed this length in most deployments. However, if you are also using keystone.conf [identity] driver = ldap, Fernet tokens may not be built using an efficient packing method, depending on the IDs returned from LDAP, resulting in longer Fernet tokens (adjust your max_token_size accordingly).