There is a requirement to create EMR jobs that sift through all web server logs and error logs to pull statistics on clickstream and errors based on client IP address. The web application uses HTTPS and is behind a Classic Load Balancer. How can the application be configured based on the above requirements?

Answer options:

A.Modify the application code to get the client IP from the X-Forwarded-Proto header or the X-Forwarded-Port header.
B.Configure ELB access logs. Then create a Data Pipeline job that imports the logs from an S3 bucket into EMR for analyzing and output the EMR data into a new S3 bucket.
C.Modify the application code to get the client IP from the x-forwarded-for header.
D.Configure ELB error logs and create a Data Pipeline job that imports the logs from an S3 bucket into EMR for analyzing and outputs the EMR data into a new S3 bucket.

Answer – C
Option A is incorrect because the X-Forwarded-Proto header is used to determine the protocol used between the client and the load balancer. And X-Forwarded-Port header is used to identify the destination port that the client used to connect to the load balancer.
Option B is incorrect because it does not specify how error logs would be configured and analyzed. ELB access logs do not tell the errors in the application layer.
Option C is CORRECT because the web server can get the client IP address from the x-forwarded-for header for HTTP/HTTPS traffic. 
Option D is incorrect because it does not specify how access logs would be configured and analyzed. ELB error logs do not contain the required information.
For more information on HTTP Headers and Classic ELB, please refer to the links below:
https://docs.aws.amazon.com/elasticloadbalancing/latest/classic/x-forwarded-headers.html