Wednesday, September 15, 2010

Axapta AOS cluster

Setting up the Axapta Cluster environment

The Axapta Object Server environment offers a load balancing feature - called the Axapta Object Server Cluster. A number of object servers can be assigned to the same Axapta Object Server Cluster. A client is configured to connect to a Cluster. It will then choose the server with the lowest number of on-line users. With this approach the Axapta Object Server Environment can also be made fault tolerant. If an Object Server fails, a client can immediately connect to one of the other servers in the same cluster.

Axapta object server cluster

The Axapta Object Server cluster environment is build to provide load balancing and fall back. An Axapta Object Server can be specified to belong to a specific cluster. If the same cluster name is given for a number of object servers they all belong to the same cluster. A user can be specified to connect to a given cluster.

Suppose a number of servers are set up in the same cluster - named AOSC. They should all use the same application and database, and in other aspects have the same settings. All clients connecting to the AOSC should be specified to search for servers belonging to this cluster; otherwise the load balancing mechanism will not work properly. A client starting up against an Axapta Object Server Cluster will start out by broadcasting an UDP package requesting Axapta Object Servers fulfilling names and IP server masks given in the client settings to respond. It is therefore vital that firewalls allow such packages to pass through. The client will receive answers from all Object Servers with information on object server name and the name of the instance plus the number of clients connected to that instance. The client disregards information from servers not belonging to the requested cluster. The client then chooses one of the instances with the lowest number of clients.

Since a client automatically can choose from all servers in a cluster one or more Object Servers can be down without changing the connection procedures. However performance might suffer severely due to higher load on the fewer servers.

Setting up the server

On the server manager select the server of interest and click settings. In the advanced field write -cluster=. The cluster name can be up to 10 characters long.

Setting up the client

In the configuration tool choose the configuration of interest. In the advanced field write -cluster=. The client setting for connecting to an object server depends on two situations. The first situation being both client and Axapta Object Servers being in the same subnet. The second being client and Axapta Object Servers belong to different subnets.

Recall the settings in the configuration utility for connecting to an object server:

* Axapta Object Server Mask
* Axapta Object Server host names
* Axapta Object Server IP Address masks

When the client and Object Servers belong to the same subnet the above three masks can be left blank.

When the client and Object Servers belong to different subnets the IP Address masks should contain the mask for the subnet the Object Servers belong to. An example could be 192.88.253.255, where the last 255 specifies that the search is done among servers in the subnet 192.88.253.*.

Note: If client at any time receives only service response from Object Servers within the same cluster it will automatically choose the least loaded of these servers without having to specify the cluster name in the
client configuration. This means that if your installation is one single Axapta cluster, there is no need to change the existing configuration with respect to cluster name. Just ensure that all relevant Object Servers are
located by client configurations network setup.
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