Administrating Multi-Server Domains With Oracle CEP Native Clustering 7-11
6.
Stop the server you just started. See
Section 7.5, Starting and Stopping an Oracle CEP Server in a Multi-Server Domain
.
7.
Copy the .msasig.dat file you created in step 5 to the other servers. For example:
prompt cd d:\oracle_cep\user_projects\domains\mydomain\server1 prompt cp .msasig.dat ..\server2
prompt cp .msasig.dat ..\server3
8.
If you plan to use Oracle CEP Visualizer with the servers in this domain, see Section 10.5.3, How to Configure SSL in a Multi-Server Domain for Oracle CEP
Visualizer .
9.
Start all servers in your multi-server domain. See
Section 7.5, Starting and Stopping an Oracle CEP Server in a Multi-Server Domain
.
7.4 Using the Multi-Server Domain APIs to Manage Group Membership Changes
In an active-active system, applications are deployed homogeneously across several servers and are actively executing.
There are cases, however, when these homogeneously-deployed applications need to elect a primary one as the coordinator or leader. In this case, events that result from the
coordinator application are kept and passed on to the next component in the EPN; the results of secondary servers are dropped. However, if the coordinator fails, then one of
the secondary servers must be elected as the new coordinator.
To enable this in an application, the adapter or event bean, generally in the role of an event sink, must implement the
com.bea.wlevs.ede.api.cluster.GroupMembershipListener interface which allows the event sinks to listen for multi-server domain group membership
changes. At runtime, Oracle CEP automatically invokes the onMembershipChange callback method whenever membership changes occur.
The signature of the callback method is as follows: onMembershipChangeServer localIdentity, Configuration groupConfiguration;
In the implementation of the onMembershipChange callback method, the event sink uses the Server object localIdentity to verify if it is the leader. This can be done
be comparing localIdentity with the result of Configuration.getCoordinator run on the second parameter,
groupConfiguration. This parameter also allows a server to know what the current members of the group are by executing Configuration.getMembers.
In order to only keep events if it is a coordinator, the event sink must get a new Server identity every time membership in the group changes. Group membership
changes occur if, for example, another server within the group fails and is no longer the coordinator.
A similar interface com.bea.wlevs.ede.api.cluster.DomainMembershipListener exists for
listening to membership changes to the domain as a whole, rather than just changes to the group.
7-12 Oracle Complex Event Processing Administrators Guide
Note that in a hot-hot configuration, there is a non-zero delay in failure notification. If you are using the notification APIs to implement clustering, you will lose and not
process events that occur in the window between the server failure and the notification being delivered to the new master server.
For more information, see Oracle Fusion Middleware Java API Reference for Oracle Complex Event Processing.
7.5 Starting and Stopping an Oracle CEP Server in a Multi-Server Domain
To start the servers in a multi-server domain, start each server separately by running its start script. This is the same way you start a server in a standalone server domain.
See Section 3.3, Starting and Stopping an Oracle CEP Server in a Standalone-Server
Domain for details.
If you have not configured custom groups for the multi-server domain, then all servers are members of just the pre-defined domain group, which contains all the servers in
the multi-server domain, and a singleton group, one for each member server. This means, for example, if there are three servers in the multi-server domain then there are
three singleton groups.
If, however, you have configured custom groups for the multi-server domain, then the servers are members of the groups for which they have been configured, as well as the
pre-defined groups.
