Simplify InternalTestCluster.fullRestart (#50218)

With node ordinals gone, there's no longer a need for such a complicated full cluster restart
procedure (as we can now uniquely associate nodes to data folders).

Follow-up to #41652

Author: ywelsch

test/framework/src/main/java/org/elasticsearch/test/InternalTestCluster.java

@@ -53,6 +53,7 @@
 import org.elasticsearch.cluster.routing.allocation.decider.ThrottlingAllocationDecider;
 import org.elasticsearch.cluster.service.ClusterService;
 import org.elasticsearch.common.Nullable;
+import org.elasticsearch.common.Randomness;
 import org.elasticsearch.common.Strings;
 import org.elasticsearch.common.breaker.CircuitBreaker;
 import org.elasticsearch.common.component.LifecycleListener;
@@ -1729,50 +1730,29 @@ private void removeExclusions(Set<String> excludedNodeIds) {
     public synchronized void fullRestart(RestartCallback callback) throws Exception {
         int numNodesRestarted = 0;
         final Settings[] newNodeSettings = new Settings[nextNodeId.get()];
-        Map<Set<DiscoveryNodeRole>, List<NodeAndClient>> nodesByRoles = new HashMap<>();
-        Set[] rolesOrderedByOriginalStartupOrder = new Set[nextNodeId.get()];
-        final int nodeCount = nodes.size();
+        final List<NodeAndClient> toStartAndPublish = new ArrayList<>(); // we want to start nodes in one go
         for (NodeAndClient nodeAndClient : nodes.values()) {
             callback.doAfterNodes(numNodesRestarted++, nodeAndClient.nodeClient());
             logger.info("Stopping and resetting node [{}] ", nodeAndClient.name);
             if (activeDisruptionScheme != null) {
                 activeDisruptionScheme.removeFromNode(nodeAndClient.name, this);
             }
-            DiscoveryNode discoveryNode = getInstanceFromNode(ClusterService.class, nodeAndClient.node()).localNode();
             final Settings newSettings = nodeAndClient.closeForRestart(callback);
             newNodeSettings[nodeAndClient.nodeAndClientId()] = newSettings;
-            rolesOrderedByOriginalStartupOrder[nodeAndClient.nodeAndClientId()] = discoveryNode.getRoles();
-            nodesByRoles.computeIfAbsent(discoveryNode.getRoles(), k -> new ArrayList<>()).add(nodeAndClient);
+            toStartAndPublish.add(nodeAndClient);
         }
 
         callback.onAllNodesStopped();
 
-        assert nodesByRoles.values().stream().mapToInt(List::size).sum() == nodeCount;
+        // randomize start up order
+        Randomness.shuffle(toStartAndPublish);
 
-        // randomize start up order, but making sure that:
-        // 1) A data folder that was assigned to a data node will stay so
-        // 2) Data nodes will get the same node lock ordinal range, so custom index paths (where the ordinal is used)
-        //    will still belong to data nodes
-        for (List<NodeAndClient> sameRoleNodes : nodesByRoles.values()) {
-            Collections.shuffle(sameRoleNodes, random);
-        }
-        final List<NodeAndClient> startUpOrder = new ArrayList<>();
-        for (Set roles : rolesOrderedByOriginalStartupOrder) {
-            if (roles == null) {
-                // if some nodes were stopped, we want have a role for that ordinal
-                continue;
-            }
-            final List<NodeAndClient> nodesByRole = nodesByRoles.get(roles);
-            startUpOrder.add(nodesByRole.remove(0));
+        for (NodeAndClient nodeAndClient : toStartAndPublish) {
+            logger.info("recreating node [{}] ", nodeAndClient.name);
+            nodeAndClient.recreateNode(newNodeSettings[nodeAndClient.nodeAndClientId()], () -> rebuildUnicastHostFiles(toStartAndPublish));
         }
-        assert nodesByRoles.values().stream().mapToInt(List::size).sum() == 0;
 
-        for (NodeAndClient nodeAndClient : startUpOrder) {
-            logger.info("creating node [{}] ", nodeAndClient.name);
-            nodeAndClient.recreateNode(newNodeSettings[nodeAndClient.nodeAndClientId()], () -> rebuildUnicastHostFiles(startUpOrder));
-        }
-
-        startAndPublishNodesAndClients(startUpOrder);
+        startAndPublishNodesAndClients(toStartAndPublish);
 
         if (callback.validateClusterForming()) {
             validateClusterFormed();