Fix performance issue with external identity provider lookup [SAML]

[strehle]

SAML related issue, details in #2821

What version of UAA are you running?

What output do you see from curl <YOUR_UAA>/info -H'Accept: application/json'?

How are you deploying the UAA?

I am deploying the UAA

• locally only using gradlew
• using a bosh release I downloaded from bosh.io
• using cf-release
• using cf-deployment

What did you do?

1. Add many external SAML IdP to an identity zone ( > 10.000)
2. Perform a SAML to only one
3. Check login times / DB metrics / memory

SAML delegates the lookup from entiyID (external key or the SAML assertion) to spring-security-saml and in UAA there is a cache but if there are many entries there is a memory problem, e.g. https://github.com/cloudfoundry/uaa/blob/develop/server/src/main/java/org/cloudfoundry/identity/uaa/provider/saml/LoginSamlAuthenticationProvider.java#L129 reads all saml providers from DB and resolves then the needed one from SAML message (entityID)
Please include UAA logs if available.

[cf-gitbot]

We have created an issue in Pivotal Tracker to manage this:

https://www.pivotaltracker.com/story/show/187414837

The labels on this github issue will be updated when the story is started.

[strehle]

@swalchemist @Tallicia FYI