private void addReconnectListener() {
    InternalDistributedSystem.addReconnectListener(
        new InternalDistributedSystem.ReconnectListener() {
          @Override
          public void onReconnect(InternalDistributedSystem oldSystem,
              InternalDistributedSystem newSystem) {
            reinitialize(newSystem.getCache());
          }
        });
  }
For peer-to-peer the backing cache *is* what's embedded in tomcat so it's always available

@return boolean indicating whether a backing cache is available
extensions/geode-modules/src/main/java/org/apache/geode/modules/session/catalina/PeerToPeerSessionCache.java