WebLogic Administration Server - Failover / High Availability

For the last one or two years, customers are asking questions about how to enable High Availability for WebLogic Administration Server.

I designed and implemented WebLogic Administration Fail-over for a financial client back in 2004 using Veritas Hardware Cluster then in 2009, I did the same for my telecom client using HP Service guard hardware cluster.

The cost and overhead of hardware cluster makes the customer to think twice about implementing the Administration Server fail over but after Oracle acquired BEA, WebLogic Administration Server became integral part of Oracle Fusion Middleware. Meaning, the Administration server availability is mandatory for major implementations.

Here’s my rule of thumb

1 If the customer just uses WebLogic Application Server to host few Java EE applications, then the Administration Server fail over is not required (Note, Banks still wants to have Admin Server fail over).

2 The Fusion Middleware control runs on Administration Server when WebLogic is installed with other Oracle Fusion Products like Oracle Service Bus, Oracle Internet Directory, Web center and other.  When the Administration Server node goes down, the Fusion control will also go down. When the monitoring components and associated logic is written into FMW control, then the administration server availability is mandatory.

Some products enabled their application monitoring logic through Administration Server (Ex: Amdocs Order Management)

Note: Failure of Administration Server will not affect the run time and life cycle operations of Managed Servers. The configuration changes can’t be done until the Administration Server comes up.

How to enable Administration Server fail over/HA

Myth

1. I can use Hardware Load balancer in front of Administration Server fail over

Answer: NO, Administration Server is Singleton and No Active-Active, No Active-Passive. It can always run only one physical server or VM and can’t be replicated due to the security and design constraints.

2. I can use WebLogic Cluster for Administration Server fail over

Answer: NO, Administration Server is Singleton and it is not clusterable. Moreover WebLogic Cluster provides Session fail over for the deployed components with some load distribution and it is always requires an external component like Proxy Plug-In or Hardware Load balancer to fail over.

Methods to implement Administration Server fail over/HA

1 Using Hardware Cluster (Automatic fail over)

The diagram below explains the Hardware cluster functionality and the following fail over scenario is applicable

·      

• The hardware cluster provides floating IP (can float between two physical servers)
• Make Administration server listen on floating IP
• When the first physical node fails, the floating IP moves to second physical server and the administration server can be restarted using rc scripts or hardware cluster package scripts
• The Administration server data (Embedded LDAP, pointers) exists on NAS
• Managed servers were started through Administration server floating IP (with possible DNS) and they don’t see any difference regarding to administration server physical location.

2 Manual fail over

    A. After creating the WebLogic domain on the first physical server (with required managed 

    server entries), copy the whole domain into the second physical server.

    B. Make the Administration Server listens on a DNS address and the DNS address must be resolved to both the physical hosts.

C. Administration Server runs on first physical server and the managed servers started through administration server DNS listen address

     D. When first physical server fails, login into second physical server and start the

    administration server

The Managed Server won’t see any difference. Note, this is applicable only when the domain goes through minimum level changes for application roll out, configuration changes. The best practice is to copy the whole domain into the second physical server whenever the domain configuration changes at the first physical server.

Another best practice is to keep the domain (at least the Admin Server and config folders) on the NAS and the shared data avoids the above critical ‘copy’ work.

From my experience, WebLogic Administration Server availability is critical for Oracle Fusion Middleware based implementations. 

Good luck. If you have any questions/suggestions, please contact me.

Happy WebLogic journey!