For the last one or two years, customers are asking
questions about how to enable High Availability for WebLogic Administration
Server.
2. I can use WebLogic Cluster for Administration Server fail over
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.
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
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
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!