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Last updated：2021-05-26 16:59:41
Server Load Balancing (SLB) is a network service that distributes traffic to multiple backend servers. SLB allows you to increase the service capability of your application system by using traffic distribution. It hides the real service port to enhance the security of the internal system. It also improves the reliability of your application system by eliminating single points of failure (SPOFs).
You can set virtual IP addresses (VIPs) for an SLB instance to virtualize multiple backend servers in the same region into a highly available and high-performance application server pool. Then, SLB distributes client requests to servers in the server pool based on forwarding rules.
SLB also checks the health of servers in the server pool and automatically isolates abnormal servers to eliminate SPOFs and improve the overall service capabilities of applications.
Kingsoft Cloud SLB features high performance, high stability, high security, and cost-effectiveness. It is applicable to scenarios such as enterprises, communities, e-commerce, and gaming.
SLB consists of the following components:
High availability
Kingsoft Cloud SLB can group multiple servers into a highly available and high-performance application server cluster, and distributes network requests to the servers in the cluster based on forwarding rules. If you enable health check, Kingsoft Cloud SLB also checks the health of the servers, and distributes requests only to healthy ones, improving service availability and stability.
Flexibility
Kingsoft Cloud SLB allows you to adjust listener ports and real server ports by using the SLB console.
Security
Kingsoft Cloud SLB can be used with Virtual Private Cloud (VPC) to provide stable network connections and security. In addition, SLB provides protection against 5 Gbit/s SYN flood attacks for free. SLB is applicable to scenarios such as enterprises, communities, e-commerce, and gaming.
You can easily upload SSL certificates by using Kingsoft Cloud Certificate Management (KCM), and create HTTPS listeners to enable SSL for your sites and applications.
Implementation
An SLB instance receives requests from clients and routes the requests to backend servers, which process the requests.
The SLB service is implemented by using listeners. Listeners added to an SLB instance listen to client requests and distribute the client requests to backend servers based on the configured forwarding policy. Listeners are configured with a protocol and a port for client-to-SLB connections, and a protocol and a port for SLB-to-backend server connections.
Request routing
A client accesses the SLB service by using a domain name. Before a client request is sent to an SLB instance, the DNS server resolves the SLB domain name and returns to the client the corresponding SLB IP address. When the SLB listener receives requests, it distributes them to backend servers based on different scheduling algorithms. Currently, Kingsoft Cloud supports the following algorithms: round robin, least connections, weighted round robin, and weighted least connections.
Monitoring backend server status
An SLB instance can monitor the operating status of its backend servers. An SLB instance forwards traffic only to backend servers that are operating properly. When the SLB instance detects that a backend server is not operating properly, it stops forwarding traffic to the backend server. When the backend server recovers, the SLB instance continues to forward traffic to the backend server.
Pure Mode
