Fail allocation of new primaries in empty cluster (#43284)

Today if you create an index in a cluster without any data nodes then it will
report yellow health because it never attempts to assign any shards if there
are no data nodes, so the new shards remain at `AllocationStatus.NO_ATTEMPT`.
This commit moves the new primaries to `AllocationStatus.DECIDERS_NO` in this
situation, causing the cluster health to move to red.

Fixes #41073

server/src/main/java/org/elasticsearch/cluster/routing/allocation/allocator/BalancedShardsAllocator.java

@@ -29,6 +29,7 @@ import org.elasticsearch.cluster.routing.RoutingNode;
 import org.elasticsearch.cluster.routing.RoutingNodes;
 import org.elasticsearch.cluster.routing.ShardRouting;
 import org.elasticsearch.cluster.routing.ShardRoutingState;
+import org.elasticsearch.cluster.routing.UnassignedInfo;
 import org.elasticsearch.cluster.routing.UnassignedInfo.AllocationStatus;
 import org.elasticsearch.cluster.routing.allocation.AllocateUnassignedDecision;
 import org.elasticsearch.cluster.routing.allocation.AllocationDecision;
@@ -115,7 +116,7 @@ public class BalancedShardsAllocator implements ShardsAllocator {
     @Override
     public void allocate(RoutingAllocation allocation) {
         if (allocation.routingNodes().size() == 0) {
-            /* with no nodes this is pointless */
+            failAllocationOfNewPrimaries(allocation);
             return;
         }
         final Balancer balancer = new Balancer(logger, allocation, weightFunction, threshold);
@@ -141,6 +142,22 @@ public class BalancedShardsAllocator implements ShardsAllocator {
         return new ShardAllocationDecision(allocateUnassignedDecision, moveDecision);
     }
 
+    private void failAllocationOfNewPrimaries(RoutingAllocation allocation) {
+        RoutingNodes routingNodes = allocation.routingNodes();
+        assert routingNodes.size() == 0 : routingNodes;
+        final RoutingNodes.UnassignedShards.UnassignedIterator unassignedIterator = routingNodes.unassigned().iterator();
+        while (unassignedIterator.hasNext()) {
+            final ShardRouting shardRouting = unassignedIterator.next();
+            final UnassignedInfo unassignedInfo = shardRouting.unassignedInfo();
+            if (shardRouting.primary() && unassignedInfo.getLastAllocationStatus() == AllocationStatus.NO_ATTEMPT) {
+                unassignedIterator.updateUnassigned(new UnassignedInfo(unassignedInfo.getReason(), unassignedInfo.getMessage(),
+                        unassignedInfo.getFailure(), unassignedInfo.getNumFailedAllocations(), unassignedInfo.getUnassignedTimeInNanos(),
+                        unassignedInfo.getUnassignedTimeInMillis(), unassignedInfo.isDelayed(), AllocationStatus.DECIDERS_NO),
+                    shardRouting.recoverySource(), allocation.changes());
+            }
+        }
+    }
+
     /**
      * Returns the currently configured delta threshold
      */

server/src/test/java/org/elasticsearch/cluster/SimpleDataNodesIT.java

@@ -85,7 +85,7 @@ public class SimpleDataNodesIT extends ESIntegTestCase {
         final ClusterHealthResponse healthResponse1 = client().admin().cluster().prepareHealth()
             .setWaitForEvents(Priority.LANGUID).execute().actionGet();
         assertThat(healthResponse1.isTimedOut(), equalTo(false));
-        assertThat(healthResponse1.getStatus(), equalTo(ClusterHealthStatus.YELLOW)); // TODO should be RED, see #41073
+        assertThat(healthResponse1.getStatus(), equalTo(ClusterHealthStatus.RED));
         assertThat(healthResponse1.getActiveShards(), equalTo(0));
 
         internalCluster().startNode(Settings.builder().put(Node.NODE_DATA_SETTING.getKey(), true).build());
@@ -104,7 +104,7 @@ public class SimpleDataNodesIT extends ESIntegTestCase {
         final ClusterHealthResponse healthResponse1 = client().admin().cluster().prepareHealth()
             .setWaitForEvents(Priority.LANGUID).execute().actionGet();
         assertThat(healthResponse1.isTimedOut(), equalTo(false));
-        assertThat(healthResponse1.getStatus(), equalTo(ClusterHealthStatus.YELLOW)); // TODO should be RED, see #41073
+        assertThat(healthResponse1.getStatus(), equalTo(ClusterHealthStatus.RED));
         assertThat(healthResponse1.getActiveShards(), equalTo(0));
 
         internalCluster().startNode();

server/src/test/java/org/elasticsearch/cluster/health/ClusterHealthAllocationTests.java

@@ -0,0 +1,93 @@
+/*
+ * Licensed to Elasticsearch under one or more contributor
+ * license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch licenses this file to you under
+ * the Apache License, Version 2.0 (the "License"); you may
+ * not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+package org.elasticsearch.cluster.health;
+
+import org.elasticsearch.Version;
+import org.elasticsearch.cluster.ClusterName;
+import org.elasticsearch.cluster.ClusterState;
+import org.elasticsearch.cluster.ESAllocationTestCase;
+import org.elasticsearch.cluster.metadata.IndexMetaData;
+import org.elasticsearch.cluster.metadata.MetaData;
+import org.elasticsearch.cluster.node.DiscoveryNodeRole;
+import org.elasticsearch.cluster.node.DiscoveryNodes;
+import org.elasticsearch.cluster.routing.RoutingTable;
+import org.elasticsearch.cluster.routing.allocation.AllocationService;
+
+import java.util.Collections;
+
+public class ClusterHealthAllocationTests extends ESAllocationTestCase {
+
+    public void testClusterHealth() {
+        ClusterState clusterState = ClusterState.builder(ClusterName.DEFAULT).build();
+        if (randomBoolean()) {
+            clusterState = addNode(clusterState, "node_m", true);
+        }
+        assertEquals(ClusterHealthStatus.GREEN, getClusterHealthStatus(clusterState));
+
+        MetaData metaData = MetaData.builder()
+            .put(IndexMetaData.builder("test")
+                .settings(settings(Version.CURRENT))
+                .numberOfShards(2)
+                .numberOfReplicas(1))
+            .build();
+        RoutingTable routingTable = RoutingTable.builder().addAsNew(metaData.index("test")).build();
+        clusterState = ClusterState.builder(clusterState).metaData(metaData).routingTable(routingTable).build();
+        MockAllocationService allocation = createAllocationService();
+        clusterState = applyStartedShardsUntilNoChange(clusterState, allocation);
+        assertEquals(0, clusterState.nodes().getDataNodes().size());
+        assertEquals(ClusterHealthStatus.RED, getClusterHealthStatus(clusterState));
+
+        clusterState = addNode(clusterState, "node_d1", false);
+        assertEquals(1, clusterState.nodes().getDataNodes().size());
+        clusterState = applyStartedShardsUntilNoChange(clusterState, allocation);
+        assertEquals(ClusterHealthStatus.YELLOW, getClusterHealthStatus(clusterState));
+
+        clusterState = addNode(clusterState, "node_d2", false);
+        clusterState = applyStartedShardsUntilNoChange(clusterState, allocation);
+        assertEquals(ClusterHealthStatus.GREEN, getClusterHealthStatus(clusterState));
+
+        clusterState = removeNode(clusterState, "node_d1", allocation);
+        assertEquals(ClusterHealthStatus.YELLOW, getClusterHealthStatus(clusterState));
+
+        clusterState = removeNode(clusterState, "node_d2", allocation);
+        assertEquals(ClusterHealthStatus.RED, getClusterHealthStatus(clusterState));
+
+        routingTable = RoutingTable.builder(routingTable).remove("test").build();
+        metaData = MetaData.builder(clusterState.metaData()).remove("test").build();
+        clusterState = ClusterState.builder(clusterState).routingTable(routingTable).metaData(metaData).build();
+        assertEquals(0, clusterState.nodes().getDataNodes().size());
+        assertEquals(ClusterHealthStatus.GREEN, getClusterHealthStatus(clusterState));
+    }
+
+    private ClusterState addNode(ClusterState clusterState, String nodeName, boolean isMaster) {
+        DiscoveryNodes.Builder nodeBuilder = DiscoveryNodes.builder(clusterState.getNodes());
+        nodeBuilder.add(newNode(nodeName, Collections.singleton(isMaster ? DiscoveryNodeRole.MASTER_ROLE : DiscoveryNodeRole.DATA_ROLE)));
+        return ClusterState.builder(clusterState).nodes(nodeBuilder).build();
+    }
+
+    private ClusterState removeNode(ClusterState clusterState, String nodeName, AllocationService allocationService) {
+        return allocationService.disassociateDeadNodes(ClusterState.builder(clusterState)
+            .nodes(DiscoveryNodes.builder(clusterState.getNodes()).remove(nodeName)).build(), true, "reroute");
+    }
+
+    private ClusterHealthStatus getClusterHealthStatus(ClusterState clusterState) {
+        return new ClusterStateHealth(clusterState).getStatus();
+    }
+
+}