I recently took the Oracle Cloud Infrastructure 2019 Architect Associate exam. There was a question about Load Balancers and I only knew half the answer. I went back after the exam to search for the correct answer but had a really hard time finding it in any of the materials I had been using to study. This includes the videos and the transcripts too. Eventually I found the answer. The question I ran into is similar to the one below.
Which two will occur when a back-end server that is registered with a back end set is marked to drain connections?
A. It forcibly closes all connections to that instance after a timeout period.
B. It keeps the connections to that instance open and attempts to complete any in-flight requests.
C. It disallows new connections to that back-end server.
D. It immediately closes all existing connections to that instance.
E. It redirects the requests to a user-defined error page.
The “two” part is what threw me. I knew the first half of the answer was C. It disallows new connections to that back-end server. But had to guess at the second half. Afterwards, I eventually found a website that directed me to this url: https://docs.cloud.oracle.com/en-us/iaas/Content/Balance/Reference/sessionpersistence.htm
At the bottom of the page I did find this excerpt: “The Load Balancing service considers a server marked drain available for existing persisted sessions. New requests that are not part of an existing persisted session are not sent to that server.”
Based on this piece of information I am led to believe that the correct second half to the question is B. It keeps the connections to that instance open and attempts to complete any in-flight requests. Please feel free to respond to this and let me know your thoughts.