memcached cache not get expired

[norman shen]

We are using openstack rocky and we I check the memcached, I found

root@compute:~# telnet compute 11211
Trying 192.168.0.17...
Connected to compute.
Escape character is '^]'.
stats cachedump 15 1
ITEM c9067b617ec1e6e7f78318c19e7ce2c7f4f9dcd6 [2034 b; 0 s]

expiration time not setup for the keys. even I set all of the cache_time options, it still not get changed.

[identity]
password_hash_rounds = 4
driver = sql

[assignment]
driver = sql

[catalog]
cache_time = 300

[role]
driver = sql
cache_time = 300

[resource]
driver = sql
cache_time = 300

[application_credential]
cache_time = 300

[oslo.cache]
expiration_time = 300

[cache]
memcache_servers = compute:11211
backend = dogpile.cache.memcached
enabled = true
expiration_time = 300
cache_time = 300

[oslo_messaging_notifications]
transport_url = rabbit://stackrabbit:secret@192.168.0.5:5672/

[DEFAULT]
max_token_size = 16384
debug = True
logging_exception_prefix = ERROR %(name)s %(instance)s
logging_default_format_string = %(color)s%(levelname)s %(name)s [-%(color)s] %(instance)s%(color)s%(message)s
logging_context_format_string = %(color)s%(levelname)s %(name)s [%(global_request_id)s %(request_id)s %(project_name)s %(user_name)s%(color)s] %(instance)s%(color)s%(message)s
logging_debug_format_suffix = {{(pid=%(process)d) %(funcName)s %(pathname)s:%(lineno)d}}
admin_endpoint = http://192.168.0.5/identity
public_endpoint = http://192.168.0.5/identity

[token]
provider = fernet
cache_time = 300

[database]
connection = mysql+pymysql://root:secret@127.0.0.1/keystone?charset=utf8

[fernet_tokens]
key_repository = /etc/keystone/fernet-keys/

[credential]
key_repository = /etc/keystone/credential-keys/

[security_compliance]
unique_last_password_count = 2
lockout_duration = 10
lockout_failure_attempts = 2

[unified_limit]
cache_time = 300

[norman shen (jshen28)]

By looking at dogpile, seems adding backend_argument = memcached_expire_time:3600 under [cache] solves the problem, is it expected behavior?

[jun923.gu (gujun1989)]

I found the same issue with you. The solution you provide can solve the issue, but keystone maybe need to optimize the configurations to solve the issue completely.