split assertion

Author: ywangd

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

@@ -36,7 +36,6 @@
 import org.elasticsearch.index.shard.ShardId;
 
 import java.util.ArrayList;
-import java.util.Arrays;
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.LinkedList;
@@ -293,21 +292,23 @@ public DesiredBalance compute(
             for (MoveAllocationCommand command : commands) {
                 try {
                     final var rerouteExplanation = command.execute(routingAllocation, false);
-                    assert rerouteExplanation.decisions().type() != Decision.Type.NO;
+                    assert rerouteExplanation.decisions().type() != Decision.Type.NO : "should have thrown for NO decision";
                     if (rerouteExplanation.decisions().type() != Decision.Type.NO) {
                         final ShardRouting[] initializingShards = routingNodes.node(
                             routingAllocation.nodes().resolveNode(command.toNode()).getId()
                         ).initializing();
                         assert initializingShards.length == 1
-                            && routingAllocation.nodes()
-                                .resolveNode(command.fromNode())
-                                .getId()
-                                .equals(initializingShards[0].relocatingNodeId())
-                            : "expect one relocating shard, but got : " + List.of(initializingShards);
-                        Arrays.stream(initializingShards).forEach(shard -> {
-                            clusterInfoSimulator.simulateShardStarted(shard);
-                            routingNodes.startShard(shard, changes, 0L);
-                        });
+                            : "expect exactly one relocating shard, but got: " + List.of(initializingShards);
+                        final var initializingShard = initializingShards[0];
+                        assert routingAllocation.nodes()
+                            .resolveNode(command.fromNode())
+                            .getId()
+                            .equals(initializingShard.relocatingNodeId())
+                            : initializingShard
+                                + " has unexpected relocation source node, expect node "
+                                + routingAllocation.nodes().resolveNode(command.fromNode());
+                        clusterInfoSimulator.simulateShardStarted(initializingShard);
+                        routingNodes.startShard(initializingShard, changes, 0L);
                     }
                 } catch (RuntimeException e) {
                     logger.debug(