[Fix-15992][server] maintain slot index by iterate MasterPriorityQueue orderly (#15993)

dolphinscheduler-service/src/main/java/org/apache/dolphinscheduler/service/queue/MasterPriorityQueue.java

@@ -20,10 +20,10 @@ package org.apache.dolphinscheduler.service.queue;
 import org.apache.dolphinscheduler.common.model.Server;
 import org.apache.dolphinscheduler.common.utils.NetUtils;
 
+import java.util.Arrays;
 import java.util.Collection;
 import java.util.Comparator;
 import java.util.HashMap;
-import java.util.Iterator;
 import java.util.concurrent.PriorityBlockingQueue;
 import java.util.concurrent.TimeUnit;
 
@@ -80,15 +80,23 @@ public class MasterPriorityQueue implements TaskPriorityQueue<Server> {
 
     private void refreshMasterList() {
         hostIndexMap.clear();
-        Iterator<Server> iterator = queue.iterator();
         int index = 0;
-        while (iterator.hasNext()) {
-            Server server = iterator.next();
+        for (Server server : getOrderedElements()) {
             String addr = NetUtils.getAddr(server.getHost(), server.getPort());
             hostIndexMap.put(addr, index);
             index += 1;
         }
+    }
 
+    /**
+     * get ordered collection of priority queue
+     *
+     * @return ordered collection
+     */
+    Server[] getOrderedElements() {
+        Server[] nQueue = queue.toArray(new Server[0]);
+        Arrays.sort(nQueue, new ServerComparator());
+        return nQueue;
     }
 
     public int getIndex(String addr) {

dolphinscheduler-service/src/test/java/org/apache/dolphinscheduler/service/queue/MasterPriorityQueueTest.java

@@ -0,0 +1,101 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF 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.apache.dolphinscheduler.service.queue;
+
+import org.apache.dolphinscheduler.common.model.Server;
+
+import java.util.Arrays;
+import java.util.Date;
+import java.util.List;
+import java.util.stream.Collectors;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+public class MasterPriorityQueueTest {
+
+    @Test
+    public void getOrderedCollection() {
+
+        MasterPriorityQueue queue = new MasterPriorityQueue();
+
+        // Test empty queue
+        Server[] emptyElements = queue.getOrderedElements();
+        Assertions.assertArrayEquals(emptyElements, new Server[]{});
+
+        // Test queue with fabricated servers
+        queue.putAll(getServerList());
+        Server[] orderElements = queue.getOrderedElements();
+        Assertions.assertEquals(extractServerIds(orderElements), Arrays.asList(4, 2, 1, 3));
+
+    }
+
+    @Test
+    public void refreshMasterList() {
+        MasterPriorityQueue queue = new MasterPriorityQueue();
+
+        // Test empty queue
+        queue.clear();
+        Assertions.assertEquals(queue.getIndex("127.0.0.1:124"), -1);
+
+        // Test queue with fabricated servers
+        queue.putAll(getServerList());
+
+        Assertions.assertEquals(queue.getIndex("127.0.0.1:124"), 0);
+        Assertions.assertEquals(queue.getIndex("127.0.0.1:122"), 1);
+        Assertions.assertEquals(queue.getIndex("127.0.0.1:121"), 2);
+        Assertions.assertEquals(queue.getIndex("127.0.0.1:123"), 3);
+
+    }
+
+    private List<Server> getServerList() {
+
+        long baseTime = new Date().getTime();
+
+        Server server1 = new Server();
+        server1.setId(1);
+        server1.setHost("127.0.0.1");
+        server1.setPort(121);
+        server1.setCreateTime(new Date(baseTime - 1000));
+
+        Server server2 = new Server();
+        server2.setId(2);
+        server2.setHost("127.0.0.1");
+        server2.setPort(122);
+        server2.setCreateTime(new Date(baseTime + 1000));
+
+        Server server3 = new Server();
+        server3.setId(3);
+        server3.setHost("127.0.0.1");
+        server3.setPort(123);
+        server3.setCreateTime(new Date(baseTime - 2000));
+
+        Server server4 = new Server();
+        server4.setId(4);
+        server4.setHost("127.0.0.1");
+        server4.setPort(124);
+        server4.setCreateTime(new Date(baseTime + 2000));
+
+        return Arrays.asList(server1, server2, server3, server4);
+    }
+
+    private List<Integer> extractServerIds(Server[] servers) {
+        return Arrays.stream(servers).map(Server::getId).collect(Collectors.toList());
+    }
+
+}