The Cluster Valve object
Table of Contents
Introduction
A cluster valve is no different from any other Tomcat Valve.
The cluster valves are interceptors in the invocation 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.
org.apache.catalina.ha.tcp.ReplicationValve
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 this Valve 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
the request matches this filter pattern, the cluster assumes there has
been no session change. An example filter would look like
filter=".*\.gif|.*\.js|.*\.jpeg|.*\.jpg|.*\.png|.*\.htm|.*\.html|.*\.css|.*\.txt"
. The filter is a regular expression using
java.util.regex.
|
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
|
org.apache.catalina.ha.session.JvmRouteBinderValve
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.
|
sessionIdAttribute |
Old sessionid before failover is registered in request attributes with this attribute.
Default attribute name is org.apache.catalina.ha.session.JvmRouteOrignalSessionID.
|