AOS clusters with a dedicated load balancer

The following diagram depicts how a client establishes a connection with the AOS server in a cluster with a dedicated load-balancing AOS.

1. When the Microsoft Dynamics AX Windows client is launched, it checks its client configuration to determine the AOS server or servers it can contact. All the AOS servers listed in the client configuration are AOS servers in the named cluster. The client then initiates a handshake with an AOS server from the list. You can configure multiple AOS servers to act as load balancers. You need to list a load balancer AOS first in the client configuration utility to ensure the client attempts to contact a load balancer AOS first.

2. The load balancer responding to the initial client request queries the database and sends a list of active AOS servers in the cluster with their workload in sorted order. The workload is calculated based on the number of clients connected divided by the maximum number of clients allowed on the server.

3. The client will then try to connect to each AOS server from the list in sequence until a successful connection is established. The client will continue to use the AOS server for this session.

Note
If you move an active AOS server to the default cluster, it will no longer participate in load balancing.

• An AOS instance configured as a load balancer does not accept any client connections as an application server or a batch server. It will act only as a load balancer.

• An AOS marked as a load balancer does not require any AOS license since it does not provide any application services to the clients.

• The advantage of setting up an AOS instance as a load balancer is that the client configuration does not need to be changed if AOS servers are moved because the client is only pointing to the load balancer.

• Since the load balancer does not actually accept client connections, the hardware requirements for the load balancer are relatively low compared to an AOS acting as an application server.

• You can configure multiple AOS servers to act as load balancers. You need to list a load balancer AOS first in the client configuration utility to ensure the client connects a load balancer.

You need to have at least one AOS server configured as a dedicated load balancer to create a cluster with a dedicated load balancer. You can select the Load Balancercheck box in the Server configuration( Administration > Server configuration) form or the Cluster configuration( Administration> Cluster configuration) form to configure an AOS server as a dedicated load balancer. You need to configure at least one AOS server as a dedicated load balancer in the named cluster to have a load balanced cluster with a dedicated load balancer.

Let us assume that your cluster has five AOS servers named AOS1, AOS2, AOS3, AOS4, and AOS5. AOS1 and AOS2 are configured as dedicated load balancers. If you configure the client configuration utility with AOS1, AOS2, AOS3, AOS4, and AOS5. the following steps will take place when the Microsoft Dynamics AX Windows client is launched:

1. The client checks its configuration settings to determine which AOS servers it can contact. The client will contact AOS1 and wait until a timeout period is reached. If the client is unable to contact AOS1, it will continue with the next AOS server in the list (AOS2, AOS3, AOS4, and AOS5) until a connection is established.

2. If the client is successful in contacting any of the AOS servers, the AOS server it contacts will query the database and return a list of all active AOS servers and their workloads. In this case, the list will only include AOS3, AOS4, and AOS5 because AOS1 and AOS2 are dedicated load balancers. The elements of the list are arranged in ascending order by workload, so the least active AOS server is placed at the beginning of the list. The workload is calculated based on the number of clients connected divided by the maximum number of clients allowed on the server

3. The client now tries to connect with an active AOS server from the list. Once a connection is established with an AOS server, the client will continue to use this AOS server for the entire session.

Even though you configured AOS1 and AOS2 to act as dedicated load balancers, the client can still contact AOS3, AOS4 and AOS5 during its launch. This is because any active AOS server can act as a load balancer as well. Placing the active AOS servers in the client configuration utility allows the client to connect with an active AOS even if the dedicated load balancers are not available.