title: Single Sign-on across Tomcat servers without clustering
body: <p>We have several Tomcat servers serving content for a single domain (via an Apache httpd front end.)  We do this to balance memory usage on one of our servlets.  That is, each server provides the same web application, but for a different data set.  We'd like to implement single sign-on on our website.</p>
  
  <p>In other words, we have httpd configured so that a visitor to <a href="http://example.com/reports/a/" rel="nofollow">http://example.com/reports/a/</a> goes to reports.war on Tomcat server A, while <a href="http://example.com/reports/b/" rel="nofollow">http://example.com/reports/b/</a> goes to reports.war on Tomcat server B.  Each URL is for a separate report, and we can't fit both reports in RAM on a single server.</p>
  
  <p>As I understand it, we can't use Tomcat clustering because that's designed for server replication, i.e. identical servers with identical data.  I've looked into session sharing via Tomcat's PersistentManager and a JDBC Store, but that appears to be designed for caching sessions, rather than sharing them.</p>
  
  <p>Am I missing something, or is this going to require a fair amount of custom coding?  (I'm willing to try another open source servlet container, such as JBoss or GlassFish, if they have this built in.)</p>