Cloned from launchpad blueprint https://blueprints.launchpad.net/keystone/+spec/reuse-token.

Description:

Now if we call the auth API with the same authentication information, the keystone will always return a new token.  This behavior sometimes will bloat the token table with valid tokens when the auth API is called too often and the expiration time is long.

This BP tries to reuse the same token when the existing token has the same scope as the expected new one. We try to reuse the existing token if the expiry time is within a scope ( threshold). We will not change the reused token's expiry time, i.e. we return the old token as it is.

the IRC discussion logs:
https://docs.google.com/document/d/1RUARZCQzbS4QnXV3Mod3ZLg9oj-oHR_kR0S6APiVk1A/edit?usp=sharing

Specification URL (additional information):

None