That has always been a risk with the memcache backend. Keystone does handle it a bit more gracefully now. I still recommend keeping the TTL as low as possible, 24 hours is a long time. The lower the TTL the less likely you will run into issues.
The only real issue you will run into now is exceeding the page-limit size, which will prevent new tokens from being issued until some tokens expire out (for that specific user). This is not something easy to fix because it is a hard limit in memcache.
@Tiantian Gao,
That has always been a risk with the memcache backend. Keystone does handle it a bit more gracefully now. I still recommend keeping the TTL as low as possible, 24 hours is a long time. The lower the TTL the less likely you will run into issues.
The only real issue you will run into now is exceeding the page-limit size, which will prevent new tokens from being issued until some tokens expire out (for that specific user). This is not something easy to fix because it is a hard limit in memcache.