We notice load balancer only supports Round Robin and Least Connections modes.

We are hoping to use "Active/Standby" mode, for example two servers A and B. We can setup A as primary, all requests go to A, only when A is down, all requests go to B. Because not all software/applications can handle sessions sharing. For example, the current MQTT server we are using does not support cluster mode. With the "Active Standby" mode, we can shift the requests to the backup server if there is a hardware problem with the primary server.

The current function "Sticky sessions" do not work for all cases, for example in our case, as our server also needs to send data to the service, let's say client A with Sticky sessions can always reach server A by using the load balancer, but our server does not know which server to send the command. That's why we need the Active Standby mode.

AlibabaCloud 's Load Balancer has this feature: https://www.alibabacloud.com/help/doc-detail/129367.htm?spm=a2c63.p38356.879954.7.617350bcUcNV2t#task-1597516