Using Oracle Web Cache 10gR2 and 11g as Load Balancer
(Doc ID 333244.1)
Last updated on MARCH 23, 2020
Applies to:Web Cache - Version 10.1.2.0.2 to 18.104.22.168.0 [Release AS10gR2 to Oracle11g]
Information in this document applies to any platform.
Portal - Version: 10.1.2.0.2 to 10.1.2.3.0
Since first releases, Web Cache has provided a lightweight load balancing mechanism that allows to distribute the client HTTP requests among several origin servers. This never was, though, the main Web Cache feature and few enhancements were done to improve it.
Now, since the Web Cache 10.1.2.0.2 release, Oracle Web Cache provides a
new and improved load balancing system recommended for all those want to have
a cheap and lightweight load balancer in front of their applications.
Specifically, this patch is recommended for all Portal users.
An example of this architecture is:
Web Cache CACHING1 ---> Origin Server 1
Web Cache LBR ---->
Web Cache CACHING2 ---> Origin Server 2
When using Web Cache only for something other than caching, such as a LBR, you are creating a bottleneck. This may be acceptable in some cases and not so in other cases.
In this configuration, Web Cache is not a true a Software LBR as it handles only HTTP and HTTPS protocols.
Configuring Web Cache as a Software LBR should ONLY be used for managing traffic to a low-volume, departmental, or test Web sites.
- Doesn't cache anything
- Ignores compression settings
- Doesn't assemble ESI content
- End-user performance monitoring can't be used
- Should not be part of a Cache cluster
- Becomes a single point of failure (as you cannot cluster for LB only mode)
- There is an additional network hop
- Overall performance will go down
Oracle Development/Support's stand on the LB only feature in Web Cache:
- It is a supported feature with limitations
- Was introduced as a LB-only mode switch to make configuring easy.
- Hardware solutions can work at Layer 2 protocol and are the fastest and most reliable.
- Next is the OS (or Kernel) level solutions that can work in both Layer 2 and Layer 7.
- But, Web Cache LB is a software solution that works only at Layer 7.
- Web Cache incurs the overhead of being an HTTP listener, like:
- URL Parsing
- Header inspection
- I/O limitations on the process - File handles, resources, disk i/o, etc.
- Also, Web Cache is a single point of Failure in this mode.
Having said the above, Oracle will support this feature to the best we can. Oracle can not promise to be better than a hardware solution or operating system solution. This is because it is not feasible.
The LB only feature in Web Cache should be used in a non-critical environment where occasional failures are acceptable. Since every customer environment varies, Oracle cannot promise a certain level of throughput. Oracle will support any code related bugs and help in tuning the Web Cache's configuration file(s) if needed.
In summary, if Web Cache is configured as Load Balancer then most of its features are disabled and you'll need to add more Web Cache nodes if you want some other features like caching or ESI assembly.
Another point to take in consideration is that this deployment makes the OracleAS Web Cache server a single point of failure for your application. You can instead configure a cache cluster with multiple OracleAS Web Cache servers in conjunction with operating system load balancing capabilities. Please check the Web Cache documentation if you want to configure this.
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In this Document
|How to configure Web Cache as Load Balancer|
|Mapping the Web Cache Load Balancer to the Origin Servers|
|How to check if Web Cache is load balancing correctly|