Chapter 6: Clusters and Synchronization  Configuring a cluster

Chapter 6: Clusters and Synchronization

Cluster overview

Each cluster includes a primary server, a group of participating servers, and a set of name servers:

Cluster support is tightly integrated with the EAServer naming service, so that all client services from a cluster are made available through the naming service. See Chapter 5, “Naming Services” for more information.

Typically, each server in a cluster runs on a different host, so each server has its own copy of the entire repository and all files required for component execution. Sybase recommends that you run each cluster member from its own installation directory.

NoteCluster members can be on different platforms Beginning with EAServer version 4.0, a cluster can include servers on different platforms, including Windows, Solaris, AIX, HP, and Linux. Each server in the cluster must be the same version of EAServer. If the cluster uses PowerBuilder components, all the servers must use the same version of the PBVM.

Figure 6-1 illustrates a server cluster and uses hostA as the primary server to synchronize the participating servers, including the name servers. Each server in the cluster is named “Jaguar.”

Figure 6-1: EAServer cluster

NoteThe SessionManager::Session::lookup operation implicitly consults the naming service, so you can write a client that does not explicitly use the naming service but still takes advantage of cluster services. For example, the PowerBuilder connection object uses SessionManager::Session::lookup.


Cluster servers

Each server can be a member of only one cluster. To provide high availability, there should be at least two name servers defined for a cluster.

Servers are defined by URL, rather than by server name. Every server in a cluster can have the same name. If you are not using partitioning, it is easy to add a new machine to a cluster; simply change the host in each listener to the Internet host name or IP address. Then, connect EAServer Manager to the cluster’s primary server and synchronize the cluster.

NoteDo not use localhost listeners in clusters Servers running in a cluster cannot have localhost IIOP listeners. The sole exception is a cluster where all servers in the cluster run on one machine. In this case, all IIOP listeners must use the same host name, which can be localhost or the machine name.

A name server can be used by one or more clusters. See “Adding a name server to a cluster” for restrictions before you assign a name server to more than one cluster.

All servers in a cluster should share a common account that will be used for inter-server connections when synchronizing the cluster. This must be a jagadmin account or an account for a user that has the Admin role.

If the servers in a cluster do not share a common account, you can synchronize the cluster only on a server-by-server basis.





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