Weblogic Clustering

WebLogic cluster is group of managed servers from a domain that will act in a coordinate fashion to provide a single server view for the client. Use WebLogic clusters to improve efficiency, scalability, load-balancing and failover. WebLogic cluster is a process level cluster, where the participating servers can be on a different physical machine or on the same machine.

IP Multicast is the backbone for exchanging heart beat signals in a cluster. So make sure multicast traffic is enabled in the WebLogic Server network.

Tips

1. If you use Web Server proxies, configure at least two, to avoid a single point of failure for the cluster.

2. When porting an application from one WebLogic Server to a cluster, ensure that objects stored in an HTTP session are able to serialize.

3. Put at least three WebLogic Server instances in each cluster, so that failure of a server does not stop load balancing of the cluster.

4. You cannot add the admin server to a cluster.

5. Use separate multicast address for each cluster in a network.

6. Servers running in a cluster can listen on different ports from WebLogic Server 7.0

7. If available use separate hardware (NIC) to route cluster multicast traffic by configuring network channels to separate internal cluster traffic from outside client traffic for better performance.

8. Combine frequently accessed applications in one tier of clusters (ex. war and EJB jar) to avoid network traffic.

9. To enable automatic failover of servlets and JSP, use replication technique.

10. In-memory replication is faster than other type of replications.

11. When using in-memory replication, specify the machine information for servers in a cluster.

12. Define replication groups only if you require control over the secondary selection process.

13. Using server affinity wherever possible will improve performance.

14. Use publicly available DNS names to identify the WebLogic Server instances rather than using IP addresses in firewall-enabled environments.

15. If a WebLogic cluster spans multiple sites, the network among the sites must support multicast traffic for cross-site clustering.

16. With this spanning architecture, you must configure the cluster's Multicast TTL value high enough to prevent routers from dropping multicast packets before they reach their destinations.