BigMemory 4.3.6 | BigMemory Max Best Practices | Manage Sessions in a Cluster
 
Manage Sessions in a Cluster
*Make sure the configured time zone and system time is consistent between all application servers. If they are different a session may appear expired when accessed on different nodes.
*Set -Dcom.tc.session.debug.sessions=true and -Dcom.tc.session.debug.invalidate=true to generate more debugging information in the client logs.
*All clustered session implementations (including Terracotta Sessions) require a mutated session object be put back into the session after it's mutated. If the call is missing, then the change isn't known to the cluster, only to the local node. For example:
Session session = request.getSession();
Map m = session.getAttribute("foo");
m.clear();
session.setAttribute("foo", m); // Without this call, the clear() is not effective across the cluster.
Without a setAttribute() call, the session becomes inconsistent across the cluster. Sticky sessions can mask this issue, but as soon as the session is accessed on another node, its state does not match the expected one. To view the inconsistency on a single client node, add the Terracotta property -Dcom.tc.session.clear.on.access=true to force locally cached sessions to be cleared with every access.
If third-party code cannot be refactored to fix this problem, and you are running Terracotta 3.6.0 or higher, you can write a servlet filter that calls setAttribute() at the end of every request. Note that this solution may substantially degrade performance.
package controller.filter;

import java.io.IOException;
import java.util.Enumeration;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpSession;

public class IterateFilter implements Filter {

public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
throws IOException, ServletException {
HttpSession session = ((HttpServletRequest) request).getSession();
if (session != null) {
@SuppressWarnings("rawtypes")
Enumeration e = session.getAttributeNames();
while (e.hasMoreElements()) {
String name = (String)e.nextElement();
Object value = session.getAttribute(name);
session.setAttribute(name, value);
}
}
}

public void init(FilterConfig filterConfig) throws ServletException {
// TODO Auto-generated method stub
}

public void destroy() {
// TODO Auto-generated method stub
}
}