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copied!<p>I ended up doing the following:</p> <p>Both Tomcats are always started. The application is also started on both of the Tomcats.</p> <p>A special <code>synchronization service</code> was hand-written. This service is part of the application and started along with the application startup. It is responsible for determination of the node that is currently active and which one <em>should</em> be active.</p> <p>My application used a Spring context for managing my services lifecycle. I separated it into two different contexts: a <code>wrapper</code> Spring context and a <code>child</code> Spring context.</p> <p>The <code>wrapper</code> context was started along with the application startup, always available and working on both Tomcats. The synchronization service was configured as a bean in the <code>wrapper</code> context.</p> <p>The <code>child</code> context actually included all services that my application provided for external clients. <em>This</em> is the context that I designated to be started only when current node is active and stopped when becoming passive.</p> <p><strong>How was the <code>child</code> context swithched on / off when active / passive?</strong></p> <p>This context wasn't started automatically along the application startup. When the <code>synchronization service</code> concluded that the current node should become active, an event was raised that caused the <code>child</code> context to get started, thus making all services <em>available</em> on that node. And the other way around: when the <code>synchronization service</code> concluded that the current node shuold become passive, a proper event was raise that caused the <code>child</code> context to shutdown, making all services <em>unavailable</em> on that node.</p> <p>Another important feature that was added was an <code>interceptor</code> for incoming requests. An incoming request hitting the one of the Tomcats, actually implies that the load balancer / web server has decided that the target node <em>is the currently available or preferred node</em>. In such a case, even if it happened that the target node was the passive one, it <em>should</em> now become active. So the <code>intercepror</code> would raise the same event that the <code>synchronization service</code> did, again making the <code>child</code> context to start and the services available on that node (and the <code>synchronization serivce</code>s on both Tomcats identified the switch and the formerly active node would passivate).</p>

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