Load Balancing Algorithms

Requests are routed to backend servers in sequence based on their weights. Backend servers with higher weights receive proportionately more requests, whereas equal-weighted servers receive the same number of requests.

This algorithm is typically used for short connections, such as HTTP connections.

• Flexible load balancing: When you need more refined load balancing, you can set a weight for each backend server to specify the percentage of requests to each server. For example, you can set higher weights to backend servers with better performance so that they can process more requests.
• Dynamic load balancing: You can adjust the weight of each backend server in real time when the server performance or load fluctuates.

• You need to set a weight for each backend server. If you have a large number of backend servers or your services require frequent adjustments, setting weights would be time-consuming.
• If the weights are inappropriate, the requests processed by each server may be imbalanced. As a result, you may need to frequently adjust server weights.

In addition to the number of active connections established with each backend server, each server is assigned a weight based on their processing capability. Requests are routed to the server with the lowest connections-to-weight ratio.

• Complex calculation: The weighted least connections algorithm needs to calculate and compare the number of connections established with each backend server in real time before selecting a server to route requests.
• Dependency on connections to backend servers: The algorithm routes requests based on the number of connections established with each backend server. If monitoring data is inaccurate or outdated, requests may not be distributed evenly across backend servers. The algorithm can only collect statistics on the connections between a given load balancer and a backend server, but cannot obtain the total number of connections to the backend server if it is associated with multiple load balancers.
• Too many loads on new servers: If existing backend servers have to handle a large number of requests, new requests will be routed to new backend servers. This may deteriorate new servers or even cause them to fail.

The source IP hash algorithm calculates the source IP address of each request and routes requests from the same IP address to the same backend server.

• Imbalanced loads across servers: This algorithm tries its best to ensure request consistency when backend servers are added or removed. If the number of backend servers decreases, some requests may be redistributed, causing imbalanced loads across servers.
• Complex calculation: This algorithm calculates the hash values of requests based on hash factors. If servers are added or removed, some requests may be redistributed, making calculation more difficult.

The connection ID algorithm calculates the QUIC connection ID and routes requests with the same hash value to the same backend server. A QUIC ID identifies a QUIC connection. This algorithm distributes requests by QUIC connection.

You can use this algorithm to distribute requests only to QUIC backend server groups.

This algorithm is typically used for QUIC requests.

• Session persistence: The connection ID algorithm ensures that requests with the same hash value are distributed to the same backend server.
• Data consistency: Requests with the same hash value are distributed to the same backend server.
• Load balancing: In scenarios that have high requirements for load balancing, this algorithm can distribute requests to balance loads among servers.