[Backport 2.x] Fix for bug showing incorrect awareness attributes count in AwarenessAllocationDecider

server/src/main/java/org/opensearch/cluster/routing/allocation/decider/AwarenessAllocationDecider.java

@@ -33,11 +33,14 @@
 package org.opensearch.cluster.routing.allocation.decider;
 
 import java.util.HashMap;
+import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
+import java.util.Set;
 import java.util.function.Function;
 
 import com.carrotsearch.hppc.ObjectIntHashMap;
+import com.carrotsearch.hppc.cursors.ObjectCursor;
 import org.opensearch.cluster.metadata.IndexMetadata;
 import org.opensearch.cluster.routing.RoutingNode;
 import org.opensearch.cluster.routing.ShardRouting;
@@ -207,12 +210,14 @@ private Decision underCapacity(ShardRouting shardRouting, RoutingNode node, Rout
 
             int numberOfAttributes = nodesPerAttribute.size();
             List<String> fullValues = forcedAwarenessAttributes.get(awarenessAttribute);
+
             if (fullValues != null) {
-                for (String fullValue : fullValues) {
-                    if (shardPerAttribute.containsKey(fullValue) == false) {
-                        numberOfAttributes++;
-                    }
+                // If forced awareness is enabled, numberOfAttributes = count(distinct((union(discovered_attributes, forced_attributes)))
+                Set<String> attributesSet = new HashSet<>(fullValues);
+                for (ObjectCursor<String> stringObjectCursor : nodesPerAttribute.keys()) {
+                    attributesSet.add(stringObjectCursor.value);
                 }
+                numberOfAttributes = attributesSet.size();
             }
             // TODO should we remove ones that are not part of full list?
 

server/src/test/java/org/opensearch/cluster/routing/allocation/AwarenessAllocationTests.java

@@ -35,23 +35,32 @@
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
 import org.opensearch.Version;
+import org.opensearch.cluster.ClusterName;
 import org.opensearch.cluster.ClusterState;
 import org.opensearch.cluster.OpenSearchAllocationTestCase;
 import org.opensearch.cluster.metadata.IndexMetadata;
 import org.opensearch.cluster.metadata.Metadata;
 import org.opensearch.cluster.node.DiscoveryNodes;
+import org.opensearch.cluster.routing.RoutingNode;
+import org.opensearch.cluster.routing.RoutingNodes;
 import org.opensearch.cluster.routing.RoutingTable;
 import org.opensearch.cluster.routing.ShardRouting;
 import org.opensearch.cluster.routing.ShardRoutingState;
 import org.opensearch.cluster.routing.allocation.command.AllocationCommands;
 import org.opensearch.cluster.routing.allocation.command.CancelAllocationCommand;
 import org.opensearch.cluster.routing.allocation.command.MoveAllocationCommand;
+import org.opensearch.cluster.routing.allocation.decider.AllocationDeciders;
 import org.opensearch.cluster.routing.allocation.decider.AwarenessAllocationDecider;
 import org.opensearch.cluster.routing.allocation.decider.ClusterRebalanceAllocationDecider;
+import org.opensearch.cluster.routing.allocation.decider.Decision;
 import org.opensearch.cluster.routing.allocation.decider.ThrottlingAllocationDecider;
+
+import org.opensearch.common.settings.ClusterSettings;
 import org.opensearch.common.settings.Settings;
 
+import java.util.Collections;
 import java.util.HashMap;
+import java.util.List;
 import java.util.Map;
 
 import static java.util.Collections.singletonMap;
@@ -971,4 +980,87 @@ public void testMultipleAwarenessAttributes() {
         assertThat(clusterState.getRoutingNodes().shardsWithState(STARTED).size(), equalTo(2));
         assertThat(clusterState.getRoutingNodes().shardsWithState(INITIALIZING).size(), equalTo(0));
     }
+
+    public void testAllocationExplainForUnassignedShardsWithUnbalancedZones() {
+        Settings settings = Settings.builder()
+            .put("cluster.routing.allocation.node_concurrent_recoveries", 10)
+            .put(ThrottlingAllocationDecider.CLUSTER_ROUTING_ALLOCATION_NODE_INITIAL_REPLICAS_RECOVERIES_SETTING.getKey(), 10)
+            .put(ClusterRebalanceAllocationDecider.CLUSTER_ROUTING_ALLOCATION_ALLOW_REBALANCE_SETTING.getKey(), "always")
+            .put("cluster.routing.allocation.awareness.attributes", "zone")
+            .put("cluster.routing.allocation.awareness.force.zone.values", "a,b,c")
+            .build();
+
+        AllocationService strategy = createAllocationService(settings);
+
+        logger.info("Building initial routing table for 'testAllocationExplainForUnassignedShardsWithUnbalancedZones'");
+        Metadata metadata = Metadata.builder()
+            .put(IndexMetadata.builder("test").settings(settings(Version.CURRENT)).numberOfShards(1).numberOfReplicas(2))
+            .build();
+
+        RoutingTable initialRoutingTable = RoutingTable.builder().addAsNew(metadata.index("test")).build();
+
+        ClusterState clusterState = ClusterState.builder(ClusterName.CLUSTER_NAME_SETTING.getDefault(Settings.EMPTY))
+            .metadata(metadata)
+            .routingTable(initialRoutingTable)
+            .build();
+
+        logger.info("--> adding 3 nodes in different zones and do rerouting");
+        clusterState = ClusterState.builder(clusterState)
+            .nodes(
+                DiscoveryNodes.builder()
+                    .add(newNode("A-0", singletonMap("zone", "a")))
+                    .add(newNode("A-1", singletonMap("zone", "a")))
+                    .add(newNode("B-0", singletonMap("zone", "b")))
+            )
+            .build();
+        clusterState = strategy.reroute(clusterState, "reroute");
+        assertThat(clusterState.getRoutingNodes().shardsWithState(STARTED).size(), equalTo(0));
+        assertThat(clusterState.getRoutingNodes().shardsWithState(INITIALIZING).size(), equalTo(1));
+
+        logger.info("--> start the shard (primary)");
+        clusterState = startInitializingShardsAndReroute(strategy, clusterState);
+        assertThat(clusterState.getRoutingNodes().shardsWithState(STARTED).size(), equalTo(1));
+        assertThat(clusterState.getRoutingNodes().shardsWithState(INITIALIZING).size(), equalTo(1));
+        // One Shard is unassigned due to forced zone awareness
+        assertThat(clusterState.getRoutingNodes().shardsWithState(UNASSIGNED).size(), equalTo(1));
+
+        List<ShardRouting> unassignedShards = clusterState.getRoutingTable().shardsWithState(UNASSIGNED);
+
+        ClusterSettings EMPTY_CLUSTER_SETTINGS = new ClusterSettings(Settings.EMPTY, ClusterSettings.BUILT_IN_CLUSTER_SETTINGS);
+        // Add a new node in zone c
+        clusterState = ClusterState.builder(clusterState)
+            .nodes(DiscoveryNodes.builder(clusterState.nodes()).add(newNode("C-0", singletonMap("zone", "c"))))
+            .build();
+
+        final AwarenessAllocationDecider decider = new AwarenessAllocationDecider(settings, EMPTY_CLUSTER_SETTINGS);
+
+        final RoutingAllocation allocation = new RoutingAllocation(
+            new AllocationDeciders(Collections.singleton(decider)),
+            clusterState.getRoutingNodes(),
+            clusterState,
+            null,
+            null,
+            0L
+        );
+        allocation.debugDecision(true);
+
+        Decision decision = null;
+        RoutingNodes nodes = clusterState.getRoutingNodes();
+
+        for (RoutingNode node : nodes) {
+            // Try to allocate unassigned shard to A-0, fails because of forced zone awareness
+            if (node.nodeId().equals("A-0")) {
+                decision = decider.canAllocate(unassignedShards.get(0), node, allocation);
+                assertEquals(Decision.Type.NO, decision.type());
+                assertEquals(
+                    decision.getExplanation(),
+                    "there are too many copies of the shard allocated to nodes with attribute"
+                        + " [zone], there are [3] total configured shard copies for this shard id and [3]"
+                        + " total attribute values, expected the allocated shard count per attribute [2] to"
+                        + " be less than or equal to the upper bound of the required number of shards per attribute [1]"
+                );
+            }
+
+        }
+    }
 }