High availability provides access to your business components and services even if a server is unavailable.
You can use clusters to achieve high availability if:
Each cluster has at least two member servers.
Partitioning is used, and each cluster partition has at least two member servers.
To guarantee end-to-end high availability, clients should use URLs of the form “iiop://host1:9000;iiop://host2:9000;...” when performing any of the activities listed below. This ensures that no part of a client’s initialization is limited to a single point of failure. The client’s URL list should be the cluster’s server list, or a subset of that list.
Setting the location property for the PowerBuilder connection object.
Setting the URL for the creation of a SessionManager::Manager object (for C++ and Java CORBA clients).
Setting the InitialContext Provider URL property for Java clients using JNDI.
In C++ or PowerBuilder clients, the host name used in the initial URLs should not match the host name in the server’s listener definitions. To achieve this, either use IP addresses for listeners and host names in clients, or map multiple host names to the same IP address. This prevents your name server from performing the work of the member servers. For example, if the client’s IIOP connection pool decides that since it has already connected to a name server that is also a member server hosting a component that the client wants, the client does not need a connection to the preferred member server. In Java clients that use the EAServer 6.0 client runtime, there are separate connection pools for naming and non-naming purposes, so this issue is avoided.
You can support non-EAServer clients (that do not support
the EAServer-proprietary multiple URL form) by creating an EAServer
service component that, upon server start-up, writes a file containing
the stringified IOR for a multiserver URL. This IOR file can then
be read by any client using an HTTP connection.
