A cluster valve is no different from any other Tomcat Valve. The cluster valves are interceptors in the invokation chain for HTTP requests, and the clustering implementation uses these valves to make intelligent decision around data and when data should be replicated.

A cluster valve must implement the org.apache.catalina.ha.ClusterValve interface. This is a simple interface that extends the org.apache.catalina.Valve interface.

The ReplicationValve will notify the cluster at the end of a HTTP request so that the cluster can make a decision whether there is data to be replicated or not.

Attributes

Attribute Description className Set value to org.apache.catalina.ha.tcp.ReplicationValve filter For known file extensions or urls, you can use a filter to notify the cluster that the session has not been modified during this request and the cluster doesn't have to probe the session managers for changes. If there is a filter match, the cluster assumes there has been no session change. An example filter would look like filter=".*\.gif;.*\.js;.*\.jpg;.*\.png;.*\.htm;.*\.html;.*\.css;.*\.txt;" The filter uses regular expressions and each filter is delimited by a semi colon. Pattern#compile(java.lang.String) primaryIndicator Boolean value, so to true, and the replication valve will insert a request attribute with the name defined by the primaryIndicatorName attribute. The value inserted into the request attribute is either Boolean.TRUE or Boolean.FALSE primaryIndicatorName Default value is org.apache.catalina.ha.tcp.isPrimarySession The value defined here is the name of the request attribute that contains the boolean value if the session is primary on this server or not. statistics Boolean value. Set to true if you want the valve to collect request statistics. Default value is false

In case of a mod_jk failover, the JvmRouteBinderValve will replace the jvmWorker attribute in the session Id, to make future requests stick to this node. If you want failback capability, don't enable this valve, but if you want your failover to stick, and for mod_jk not to have to keep probing the node that went down, you use this valve.

Attributes

Attribute Description className org.apache.catalina.ha.session.JvmRouteBinderValve enabled Default value is true Runtime attribute to turn on and off turn over of the session's jvmRoute value.