[Enhancement] only call getAliveComputeNodes once per OlapScanNode (backport #52168)

fe/fe-core/src/main/java/com/starrocks/planner/OlapScanNode.java

@@ -189,6 +189,10 @@ public class OlapScanNode extends ScanNode {
 
     private long totalScanRangeBytes = 0;
 
+    // Set to true after it's confirmed at some point during the execution of this request that there is some living CN.
+    // Set just once per query.
+    private boolean alreadyFoundSomeLivingCn = false;
+
     // Constructs node to scan given data files of table 'tbl'.
     // Constructs node to scan given data files of table 'tbl'.
     public OlapScanNode(PlanNodeId id, TupleDescriptor desc, String planNodeName) {
@@ -500,6 +504,25 @@ public List<TScanRangeLocations> updateScanRangeLocations(List<TScanRangeLocatio
         return newLocations;
     }
 
+
+    private void checkSomeAliveComputeNode() throws ErrorReportException {
+        // Note that it's theoretically possible that there were some living CN earlier in this query's execution, and then
+        // they all died, but in that case, the problem this will be surfaced later anyway.
+        if (alreadyFoundSomeLivingCn) {
+            return;
+        }
+        // We prefer to call getAliveComputeNodes infrequently, as it can come to dominate the execution time of a query in the
+        // frontend if there are many calls per request (e.g. one per partition when there are many partitions).
+        if (RunMode.getCurrentRunMode() == RunMode.SHARED_DATA) {
+            WarehouseManager warehouseManager = GlobalStateMgr.getCurrentState().getWarehouseMgr();
+            if (CollectionUtils.isEmpty(warehouseManager.getAliveComputeNodes(warehouseId))) {
+                Warehouse warehouse = warehouseManager.getWarehouse(warehouseId);
+                throw ErrorReportException.report(ErrorCode.ERR_NO_NODES_IN_WAREHOUSE, warehouse.getName());
+            }
+        }
+        alreadyFoundSomeLivingCn = true;
+    }
+
     public void addScanRangeLocations(Partition partition,
                                       PhysicalPartition physicalPartition,
                                       MaterializedIndex index,
@@ -517,13 +540,7 @@ public void addScanRangeLocations(Partition partition,
         selectedPartitionNames.add(partition.getName());
         selectedPartitionVersions.add(visibleVersion);
 
-        if (RunMode.getCurrentRunMode() == RunMode.SHARED_DATA) {
-            WarehouseManager warehouseManager = GlobalStateMgr.getCurrentState().getWarehouseMgr();
-            if (CollectionUtils.isEmpty(warehouseManager.getAliveComputeNodes(warehouseId))) {
-                Warehouse warehouse = warehouseManager.getWarehouse(warehouseId);
-                throw ErrorReportException.report(ErrorCode.ERR_NO_NODES_IN_WAREHOUSE, warehouse.getName());
-            }
-        }
+        checkSomeAliveComputeNode();
         for (Tablet tablet : tablets) {
             long tabletId = tablet.getId();
             LOG.debug("{} tabletId={}", (logNum++), tabletId);

fe/fe-core/src/test/java/com/starrocks/server/WarehouseManagerTest.java

@@ -283,6 +283,83 @@ public RunMode getCurrentRunMode() {
         Assert.assertEquals("No alive backend or compute node in warehouse null.", ex.getMessage());
     }
 
+    @Test
+    public void testSelectWorkerGroupByWarehouseId_checkAliveNodesOnce(@Mocked WarehouseManager mockWarehouseMgr)
+            throws UserException {
+        Backend b1 = new Backend(10001L, "192.168.0.1", 9050);
+        b1.setBePort(9060);
+        b1.setAlive(false);
+        b1.setWarehouseId(WarehouseManager.DEFAULT_WAREHOUSE_ID);
+
+        new MockUp<NodeMgr>() {
+            @Mock
+            public SystemInfoService getClusterInfo() {
+                return systemInfo;
+            }
+        };
+
+        new MockUp<SystemInfoService>() {
+            @Mock
+            public ComputeNode getBackendOrComputeNode(long nodeId) {
+                return b1;
+            }
+        };
+
+        new MockUp<StarOSAgent>() {
+            @Mock
+            public List<Long> getWorkersByWorkerGroup(long workerGroupId) throws UserException {
+                if (workerGroupId == StarOSAgent.DEFAULT_WORKER_GROUP_ID) {
+                    return Lists.newArrayList(b1.getId());
+                }
+                return Lists.newArrayList();
+            }
+        };
+
+        new MockUp<GlobalStateMgr>() {
+            @Mock
+            public NodeMgr getNodeMgr() {
+                return nodeMgr;
+            }
+
+            @Mock
+            public StarOSAgent getStarOSAgent() {
+                return starOSAgent;
+            }
+
+            @Mock
+            public WarehouseManager getWarehouseMgr() {
+                return mockWarehouseMgr;
+            }
+
+        };
+
+        ComputeNode livingCn = new ComputeNode();
+        livingCn.setAlive(true);
+        new Expectations() {
+            {
+                // This is the point of the test -- we only want to call this once even though we're calling
+                // addScanRangeLocations multiple times.
+                mockWarehouseMgr.getAliveComputeNodes(WarehouseManager.DEFAULT_WAREHOUSE_ID);
+                times = 1;
+                result = Lists.newArrayList(livingCn);
+            }
+        };
+        new MockUp<RunMode>() {
+            @Mock
+            public RunMode getCurrentRunMode() {
+                return RunMode.SHARED_DATA;
+            }
+        };
+
+        OlapScanNode scanNode = newOlapScanNode();
+        Partition partition = new Partition(123, "aaa", null, null);
+        MaterializedIndex index = new MaterializedIndex(1, MaterializedIndex.IndexState.NORMAL);
+        scanNode.addScanRangeLocations(partition, partition, index, Collections.emptyList(), 1);
+        // Since this is the second call to  addScanRangeLocations on the same OlapScanNode, we do not expect another call to
+        // getAliveComputeNodes.
+        scanNode.addScanRangeLocations(partition, partition, index, Collections.emptyList(), 1);
+    }
+
     private OlapScanNode newOlapScanNode() {
         TupleDescriptor desc = new TupleDescriptor(new TupleId(0));
         OlapTable table = new OlapTable();