Rename decideShardAllocation to reflect allocation explain purpose (#137227)

Renames ShardsAllocator#decideShardAllocation to
ShardsAllocator#explainShardAllocation

Relates ES-12833

Author: DiannaHohensee

server/src/main/java/org/elasticsearch/cluster/routing/allocation/AllocationService.java

@@ -795,7 +795,7 @@ public ShardAllocationDecision explainShardAllocation(ShardRouting shardRouting,
         if (allocateDecision.isDecisionTaken()) {
             return new ShardAllocationDecision(allocateDecision, MoveDecision.NOT_TAKEN);
         } else {
-            return shardsAllocator.decideShardAllocation(shardRouting, allocation);
+            return shardsAllocator.explainShardAllocation(shardRouting, allocation);
         }
     }
 

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

@@ -243,7 +243,7 @@ private void collectAndRecordNodeWeightStats(Balancer balancer, BalancingWeights
     }
 
     @Override
-    public ShardAllocationDecision decideShardAllocation(final ShardRouting shard, final RoutingAllocation allocation) {
+    public ShardAllocationDecision explainShardAllocation(final ShardRouting shard, final RoutingAllocation allocation) {
         Balancer balancer = new Balancer(
             writeLoadForecaster,
             allocation,

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

@@ -246,8 +246,8 @@ public String toString() {
     }
 
     @Override
-    public ShardAllocationDecision decideShardAllocation(ShardRouting shard, RoutingAllocation allocation) {
-        return delegateAllocator.decideShardAllocation(shard, allocation);
+    public ShardAllocationDecision explainShardAllocation(ShardRouting shard, RoutingAllocation allocation) {
+        return delegateAllocator.explainShardAllocation(shard, allocation);
     }
 
     @Override

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

@@ -77,13 +77,8 @@ default RoutingExplanations execute(RoutingAllocation allocation, AllocationComm
      * then the {@link AllocateUnassignedDecision} will be non-null.  If the shard is not in the unassigned
      * state, then the {@link MoveDecision} will be non-null.
      *
-     * This method is primarily used by the cluster allocation explain API to provide detailed explanations
-     * for the allocation of a single shard.  Implementations of the {@link #allocate(RoutingAllocation)} method
-     * may use the results of this method implementation to decide on allocating shards in the routing table
-     * to the cluster.
-     *
      * If an implementation of this interface does not support explaining decisions for a single shard through
      * the cluster explain API, then this method should throw a {@code UnsupportedOperationException}.
      */
-    ShardAllocationDecision decideShardAllocation(ShardRouting shard, RoutingAllocation allocation);
+    ShardAllocationDecision explainShardAllocation(ShardRouting shard, RoutingAllocation allocation);
 }

server/src/test/java/org/elasticsearch/action/admin/cluster/allocation/ClusterAllocationExplainActionTests.java

@@ -81,7 +81,7 @@ public void allocate(RoutingAllocation allocation) {
                 }
 
                 @Override
-                public ShardAllocationDecision decideShardAllocation(ShardRouting shard, RoutingAllocation allocation) {
+                public ShardAllocationDecision explainShardAllocation(ShardRouting shard, RoutingAllocation allocation) {
                     if (shard.initializing() || shard.relocating()) {
                         return ShardAllocationDecision.NOT_TAKEN;
                     } else {

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

@@ -111,7 +111,7 @@ public void allocate(RoutingAllocation allocation) {
         }
 
         @Override
-        public ShardAllocationDecision decideShardAllocation(ShardRouting shard, RoutingAllocation allocation) {
+        public ShardAllocationDecision explainShardAllocation(ShardRouting shard, RoutingAllocation allocation) {
             throw new UnsupportedOperationException("explain API not supported on FakeShardsAllocator");
         }
     }

server/src/test/java/org/elasticsearch/cluster/routing/allocation/AllocationServiceTests.java

@@ -148,7 +148,7 @@ public void allocate(RoutingAllocation allocation) {
                 }
 
                 @Override
-                public ShardAllocationDecision decideShardAllocation(ShardRouting shard, RoutingAllocation allocation) {
+                public ShardAllocationDecision explainShardAllocation(ShardRouting shard, RoutingAllocation allocation) {
                     return ShardAllocationDecision.NOT_TAKEN;
                 }
             },

server/src/test/java/org/elasticsearch/cluster/routing/allocation/AllocationStatsServiceTests.java

@@ -215,7 +215,7 @@ public void allocate(RoutingAllocation allocation) {
             }
 
             @Override
-            public ShardAllocationDecision decideShardAllocation(ShardRouting shard, RoutingAllocation allocation) {
+            public ShardAllocationDecision explainShardAllocation(ShardRouting shard, RoutingAllocation allocation) {
                 return null;
             }
         };

server/src/test/java/org/elasticsearch/cluster/routing/allocation/BalancedSingleShardTests.java

@@ -58,7 +58,7 @@ public void testRebalanceNonStartedShardNotAllowed() {
         final ProjectId projectId = clusterState.metadata().projects().keySet().iterator().next();
 
         ShardRouting shard = clusterState.globalRoutingTable().routingTable(projectId).index("idx").shard(0).primaryShard();
-        MoveDecision rebalanceDecision = allocator.decideShardAllocation(
+        MoveDecision rebalanceDecision = allocator.explainShardAllocation(
             shard,
             newRoutingAllocation(new AllocationDeciders(Collections.emptyList()), clusterState)
         ).getMoveDecision();
@@ -75,7 +75,7 @@ public void testRebalanceNotAllowedDuringPendingAsyncFetch() {
         ShardRouting shard = clusterState.globalRoutingTable().routingTable(projectId).index("idx").shard(0).primaryShard();
         RoutingAllocation routingAllocation = newRoutingAllocation(new AllocationDeciders(Collections.emptyList()), clusterState);
         routingAllocation.setHasPendingAsyncFetch();
-        MoveDecision rebalanceDecision = allocator.decideShardAllocation(shard, routingAllocation).getMoveDecision();
+        MoveDecision rebalanceDecision = allocator.explainShardAllocation(shard, routingAllocation).getMoveDecision();
         assertNotNull(rebalanceDecision.getClusterRebalanceDecision());
         assertEquals(AllocationDecision.AWAITING_INFO, rebalanceDecision.getAllocationDecision());
         assertThat(rebalanceDecision.getExplanation(), equalTo(Explanations.Rebalance.AWAITING_INFO));
@@ -104,7 +104,7 @@ public Decision canRebalance(ShardRouting shardRouting, RoutingAllocation alloca
             new AllocationDeciders(Collections.singleton(noRebalanceDecider)),
             clusterState
         );
-        MoveDecision rebalanceDecision = allocator.decideShardAllocation(shard, routingAllocation).getMoveDecision();
+        MoveDecision rebalanceDecision = allocator.explainShardAllocation(shard, routingAllocation).getMoveDecision();
         assertEquals(canRebalanceDecision.type(), rebalanceDecision.getClusterRebalanceDecision().type());
         assertEquals(AllocationDecision.fromDecisionType(canRebalanceDecision.type()), rebalanceDecision.getAllocationDecision());
         assertThat(
@@ -247,7 +247,7 @@ public Decision canRebalance(ShardRouting shardRouting, RoutingAllocation alloca
         routingAllocation = newRoutingAllocation(new AllocationDeciders(allocationDeciders), clusterState);
         routingAllocation.debugDecision(true);
         ShardRouting shard = clusterState.getRoutingNodes().activePrimary(shardToRebalance.shardId());
-        MoveDecision rebalanceDecision = allocator.decideShardAllocation(shard, routingAllocation).getMoveDecision();
+        MoveDecision rebalanceDecision = allocator.explainShardAllocation(shard, routingAllocation).getMoveDecision();
         assertEquals(shardToRebalance.relocatingNodeId(), rebalanceDecision.getTargetNode().getId());
         // make sure all excluded nodes returned a NO decision
         for (NodeAllocationResult nodeResult : rebalanceDecision.getNodeDecisions()) {
@@ -345,7 +345,7 @@ public Decision canRebalance(ShardRouting shardRouting, RoutingAllocation alloca
         assertThat(clusterState.metadata().projects(), aMapWithSize(1));
         final ProjectId projectId = clusterState.metadata().projects().keySet().iterator().next();
 
-        return allocator.decideShardAllocation(shardRouting, routingAllocation).getMoveDecision();
+        return allocator.explainShardAllocation(shardRouting, routingAllocation).getMoveDecision();
     }
 
     private ClusterState addNodesToClusterState(ClusterState clusterState, int numNodesToAdd) {
@@ -382,7 +382,7 @@ public Decision canRebalance(ShardRouting shardRouting, RoutingAllocation alloca
 
         ShardRouting shard = clusterState.routingTable(projectId).index("idx").shard(0).primaryShard();
         RoutingAllocation routingAllocation = newRoutingAllocation(new AllocationDeciders(allocationDeciders), clusterState);
-        MoveDecision rebalanceDecision = allocator.decideShardAllocation(shard, routingAllocation).getMoveDecision();
+        MoveDecision rebalanceDecision = allocator.explainShardAllocation(shard, routingAllocation).getMoveDecision();
 
         if (rebalanceExpected == false) {
             assertAssignedNodeRemainsSame(allocator, routingAllocation, shard);

server/src/test/java/org/elasticsearch/cluster/routing/allocation/allocator/BalancedShardsAllocatorTests.java

@@ -102,7 +102,7 @@ public class BalancedShardsAllocatorTests extends ESAllocationTestCase {
     };
     private static final Settings WITH_DISK_BALANCING = Settings.builder().put(DISK_USAGE_BALANCE_FACTOR_SETTING.getKey(), "1e-9").build();
 
-    public void testDecideShardAllocation() {
+    public void testExplainShardAllocation() {
         BalancedShardsAllocator allocator = new BalancedShardsAllocator(Settings.EMPTY);
         ClusterState clusterState = ClusterStateCreationUtils.state("idx", false, ShardRoutingState.STARTED);
         assertEquals(clusterState.nodes().getSize(), 3);
@@ -125,9 +125,9 @@ public void testDecideShardAllocation() {
         RoutingAllocation allocation = createRoutingAllocation(clusterState);
 
         allocation.debugDecision(false);
-        AllocateUnassignedDecision allocateDecision = allocator.decideShardAllocation(shard, allocation).getAllocateDecision();
+        AllocateUnassignedDecision allocateDecision = allocator.explainShardAllocation(shard, allocation).getAllocateDecision();
         allocation.debugDecision(true);
-        AllocateUnassignedDecision allocateDecisionWithExplain = allocator.decideShardAllocation(shard, allocation).getAllocateDecision();
+        AllocateUnassignedDecision allocateDecisionWithExplain = allocator.explainShardAllocation(shard, allocation).getAllocateDecision();
         // the allocation decision should have same target node no matter the debug is on or off
         assertEquals(allocateDecision.getTargetNode().getId(), allocateDecisionWithExplain.getTargetNode().getId());
 
@@ -138,7 +138,7 @@ public void testDecideShardAllocation() {
         assertEquals(allocateDecision.getTargetNode().getId(), assignedShards.get(0).currentNodeId());
     }
 
-    public void testDecideShardAllocationWhenThereAreMultipleProjects() {
+    public void testExplainShardAllocationWhenThereAreMultipleProjects() {
         final int numberOfNodes = randomIntBetween(3, 8);
         final int numberOfProjects = randomIntBetween(3, 8);
 
@@ -222,7 +222,7 @@ public void testDecideShardAllocationWhenThereAreMultipleProjects() {
             .index(indexName)
             .shard(0)
             .primaryShard();
-        AllocateUnassignedDecision allocateDecision = allocator.decideShardAllocation(shard, allocation).getAllocateDecision();
+        AllocateUnassignedDecision allocateDecision = allocator.explainShardAllocation(shard, allocation).getAllocateDecision();
         final DiscoveryNode targetNode = allocateDecision.getTargetNode();
         assertThat(targetNode, notNullValue());
         assertThat(nodes.get(targetNode.getId()), sameInstance(targetNode));