[grid] Ensure a Node is purged as per the heartbeat period

Author: pujagani

java/server/src/org/openqa/selenium/grid/distributor/GridModel.java

@@ -190,15 +190,16 @@ public void purgeDeadNodes() {
       Set<NodeStatus> toRemove = new HashSet<>();
 
       for (NodeStatus node : nodes) {
+        Instant now = Instant.now();
         Instant lastTouched = nodePurgeTimes.getOrDefault(node.getNodeId(), Instant.now());
         Instant lostTime = lastTouched.plus(node.getHeartbeatPeriod().multipliedBy(PURGE_TIMEOUT_MULTIPLIER / 2));
         Instant deadTime = lastTouched.plus(node.getHeartbeatPeriod().multipliedBy(PURGE_TIMEOUT_MULTIPLIER));
 
-        if (node.getAvailability() == UP && lastTouched.isBefore(lostTime)) {
+        if (node.getAvailability() == UP && lostTime.isBefore(now)) {
           LOG.info(String.format("Switching node %s from UP to DOWN", node.getNodeId()));
           replacements.put(node, rewrite(node, DOWN));
         }
-        if (node.getAvailability() == DOWN && lastTouched.isBefore(deadTime)) {
+        if (node.getAvailability() == DOWN && deadTime.isBefore(now)) {
           LOG.info(String.format("Removing node %s that is DOWN for too long", node.getNodeId()));
           toRemove.add(node);
         }