Like mod_jk and mod_proxy, mod_cluster uses a communication channel to forward requests from httpd to one of a set of application server nodes.
Unlike mod_jk and mod_proxy, mod_cluster leverages an additional connection between the application server nodes and httpd.
Unlike mod_jk, mod_cluster also doesn't require AJP, but httpd connections to application server nodes can use HTTP, HTTPS, or AJP.
The application server nodes use this connection to transmit server-side load balance factors and lifecycle events back to httpd via a custom set of HTTP methods, affectionately called the Mod-Cluster Management Protocol (MCMP).
This additional feedback channel allows mod_cluster to offer a level of intelligence and granularity not found in other load balancing solutions.
Within httpd, mod_cluster is implemented as a set of modules for httpd with mod_proxy enabled. Much of the logic comes from mod_proxy, e.g. mod_proxy_ajp provides all the AJP logic needed by mod_cluster.
Migrating from mod_jk or mod_proxy is fairly straight forward. In general, much of the configuration previously found in httpd.conf is now defined in the application server nodes.
What is new in this release:
- Added EnableMCPMReceive in configuration.
- mod_proxy code for old httpd versions needs to be updated.
- Missing Documentation For mod_cluster with JBoss AS5.
- sticky-session-force change requires httpd restart.
- mod_cluster management console/Status does not show exact mod_cluster version.
What is new in version 1.2.6 / 1.3.1.Beta2:
- Added EnableMCPMReceive in configuration.
- mod_proxy code for old httpd versions needs to be updated.
- Missing Documentation For mod_cluster with JBoss AS5.
- sticky-session-force change requires httpd restart.
- mod_cluster management console/Status does not show exact mod_cluster version.
What is new in version 1.1.0.RC3:
- RPC failure can lead to failure to deploy a webapp.
- ManagerBalancerName doesn't work.
- NoClassDefFoundError running demo app against AS6.
- Allow override of default clean shutdown behavior.
Requirements:
- httpd-2.2.8 or higher
- JBoss AS 5.0.0+ or JBossWeb 2.1.1+
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