ACP-Cloud1 Exam Dumps : ACP Cloud Computing Certification

The X-Forwarded-For field in HTTP header is used to identify the originating IP address of a client connecting to a web server through an HTTP proxy or a load balancer. When the “Obtain the Visitor’s Real IP Address” function is enabled in Alibaba Cloud SLB, the SLB instance adds the X-Forwarded-For field to the HTTP header of each request and forwards the request to the backend server. The backend server can then obtain the real IP address of the visitor from the X-Forwarded-For field1. The format of the X-Forwarded-For field is as follows:

X-Forwarded-For: client, proxy1, proxy2

where the value is a comma+space separated list of IP addresses, the left-most being the original client, and each successive proxy that passed the request adding the IP address where it received the request from. In this example, the request passed through proxy1, proxy2, and then the SLB instance (proxy3).2

References: Obtain client IP addresses - Server Load Balancer - Alibaba Cloud, X-Forwarded-For - MDN Web Docs

Weighted Round Robin (WRR) is a load balancing mode that assigns requests to backend ECS instances based on their weights. The higher the weight of the backend ECS instance, the higher the chance that the instance will receive requests. This mode can exploit the different service capacities of backend ECS instances by setting higher weights to ECS instances with higher capacities. For example, if there are two ECS instances in the backend server pool, one with a weight of 10 and the other with a weight of 20, the ECS instance with a weight of 20 will receive twice as many requests as the ECS instance with a weight of 10.

References:

1: SLB overview - Server Load Balancer - Alibaba Cloud Documentation Center

4: Server Load Balancer - Alibaba Cloud

5: Alibaba Server Load Balancer (SLB) Course - Cloud Academy

In Alibaba Cloud RDS, read-only instances are synchronized from the master instance but do not allow actions such as creating or deleting databases, configuring backup policies, or changing account authorizations. However, you can configure the read-only instance’s whitelist to control access.