Classic Load Balancer (CLB) distributes incoming traffic across multiple backend servers based on forwarding rules, increasing application availability and scalability.
Overview
CLB uses a virtual service address to pool backend servers within the same region and distributes client requests based on your forwarding rules.
CLB runs health checks on backend servers and automatically isolates unhealthy ones, eliminating single points of failure (SPOFs). CLB also provides DDoS mitigation.
Components
Grayed-out servers have failed health checks and do not receive traffic.
CLB consists of three components:
|
Component |
Description |
|
Instance |
A running load balancing service that receives and distributes traffic to backend servers. Each CLB instance requires at least one listener and two backend servers. |
|
Listener |
Monitors client requests, forwards them to backend servers, and performs health checks. |
|
Backend server |
A compute resource that receives forwarded requests. CLB supports ECS, ECI, and ENI instances as backend servers, managed individually or in batches through vServer groups or primary/secondary server groups. |
Benefits
-
High availability
Fully redundant architecture with no single points of failure. Supports intra-city disaster recovery.
Scales elastically with traffic to maintain availability during load fluctuations.
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Scalability
Add or remove backend servers at any time to match capacity with demand.
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Cost-effectiveness
Significantly reduces fixed costs compared with traditional hardware load balancers.
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Security
Integrated with Alibaba Cloud Security, CLB provides up to 5 Gbps of DDoS protection.
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High concurrency
Supports up to one million concurrent connections per instance.
Accessing CLB
You can access and manage CLB through the following methods:
-
: a web console to create, manage, and release CLB instances. Create and manage CLB instances.
Classic Load Balancer (CLB) console: a web console to create, manage, and release CLB instances. Create and manage CLB instances. -
Alibaba Cloud SDKs: supports Java, Go, PHP, and Python.
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OpenAPI Explorer: call API operations and generate SDK code samples.
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Terraform: provision and manage CLB resources using configuration files with version control.