void overrideHeartbeatTimeoutCheck(HeartbeatTimeoutCheck newCheck) {
      checkHeartbeat = newCheck;
    }
Class <code>ClientHealthMonitorThread</code> is a <code>Thread</code> that verifies all clients
are still alive.
geode-core/src/main/java/org/apache/geode/internal/cache/tier/sockets/ClientHealthMonitor.java