Failing-over
web session caching is problematic when you run multiple application servers. It
is not uncommon for web applications to run in a cluster to distribute the load
of high volume of web requests. But what if one of the application servers
crashes? The load balancer will just route the web request to another available
application server, but all of user’s session data is lost. In simple words,
you may be filling your shopping cart with your favorite items, but if the
application server serving your request crashes, you will end up with an empty
cart.
A feasible solution here would be to cache all your web sessions
in GridGain cache. GridGain In-Memory Data Fabric WebSessions Cache is a distributed cache that maintains a copy of
all web sessions’ data in memory.
So, when an application server fails, web requests get routed to some
other application server that simply fetches the web session from GridGain cache.
This
process happens in the background and is so seamless that it does not affect
the users’ experience. Not only that, GridGain also ensures fault tolerance by either
replicating or partitioning the data, which is easily configurable, across all
grid nodes in the cluster. And so, no session data is lost.
Moreover,
a web request can now be sent to any active application server, that can access
the session data from GridGain cluster, and so, you may choose to turn off the Sticky Connections support of the load
balancer.
With just a few simple steps you can enable web
sessions caching with GridGain in your application. All you need to do is:
· gridgain.jar
· gridgain-web.jar
· gridgain-log4j.jar
· gridgain-spring.jar
Or, if you have a Maven based project, add the following to
your application's pom.xml
<dependency>
<groupId>org.gridgain</groupId>
<artifactId>gridgain-fabric</artifactId>
<version> ${gridgain.version}</version>
<type>pom</type>
</dependency>
<dependency>
<groupId>org.gridgain</groupId>
<artifactId>gridgain-web</artifactId>
<version> ${gridgain.version}</version>
</dependency>
<dependency>
<groupId>org.gridgain</groupId>
<artifactId>gridgain-log4j</artifactId>
<version>${gridgain.version}</version>
</dependency>
Make sure to replace ${gridgain.version}
2. Configure
GridGain cache in either PARTITIONED mode
<bean
class="org.gridgain.grid.cache.GridCacheConfiguration">
<!-- Cache name. -->
<property name="name"
value="partitioned"/>
<!-- Cache mode. -->
<property name="cacheMode"
value="PARTITIONED"/>
<property name="backups"
value="1"/>
...
</bean>
or REPLICATED mode
<bean
class="org.gridgain.grid.cache.GridCacheConfiguration">
<!-- Cache name. -->
<property name="name"
value="replicated"/>
<!-- Cache mode. -->
<property name="cacheMode"
value="REPLICATED"/>
...
</bean>
You can also choose
to use the default cache configuration, specified in GRIDGAIN_HOME/config/default-config.xml, shipped with GridGain installation.
3. Declare a
context listener in the application’s web.xml.
...
<listener>
<listener-class>org.gridgain.grid.startup.servlet.GridServletContextListenerStartup</listener-class>
</listener>
<filter>
<filter-name>GridGainWebSessionsFilter</filter-name>
<filter-class>org.gridgain.grid.cache.websession.GridWebSessionFilter</filter-class>
</filter>
<!-- You can also specify a custom URL pattern.
-->
<filter-mapping>
<filter-name>GridGainWebSessionsFilter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
<!-- Specify GridGain configuration (relative to
META-INF folder or GRIDGAIN_HOME). -->
<context-param>
<param-name>GridGainConfigurationFilePath</param-name>
<param-value>config/default-config.xml </param-value>
</context-param>
<!-- Specify the name of GridGain cache for web
sessions. -->
<context-param>
<param-name>GridGainWebSessionsCacheName</param-name>
<param-value>partitioned</param-value>
</context-param>
...
4. Optional – Set eviction policy
for stale web sessions data lying in cache.
<bean
class="org.gridgain.grid.cache.GridCacheConfiguration">
<!--
Cache name. -->
<property name="name" value="session-cache"/>
<!--
Set up LRU eviction policy with 10000 sessions limit. -->
<property name="evictionPolicy">
<bean
class="org.gridgain.grid.cache.eviction.lru.GridCacheLruEvictionPolicy">
<property name="maxSize" value="10000"/>
</bean>
</property>
...
</bean>
