SOLR-17560: Remove redundant getLeaderReplicas method (#3515)

To simplify & reduce weight of DocCollection.  This method was only called in one place and it doesn't seem worthy.

Author: meryemgulbudakk

solr/core/src/java/org/apache/solr/servlet/HttpSolrCall.java

@@ -889,15 +889,17 @@ protected SolrCore getCoreByCollection(String collectionName, boolean isPreferLe
       return null;
     }
     Set<String> liveNodes = clusterState.getLiveNodes();
+    List<Replica> replicas = collection.getReplicasOnNode(cores.getZkController().getNodeName());
 
     if (isPreferLeader) {
-      List<Replica> leaderReplicas =
-          collection.getLeaderReplicas(cores.getZkController().getNodeName());
-      SolrCore core = randomlyGetSolrCore(liveNodes, leaderReplicas);
-      if (core != null) return core;
+      SolrCore core = null;
+      if (replicas != null && !replicas.isEmpty()) {
+        List<Replica> leaderReplicas = replicas.stream().filter(Replica::isLeader).toList();
+        core = randomlyGetSolrCore(liveNodes, leaderReplicas);
+        if (core != null) return core;
+      }
     }
 
-    List<Replica> replicas = collection.getReplicasOnNode(cores.getZkController().getNodeName());
     return randomlyGetSolrCore(liveNodes, replicas);
   }
 

solr/core/src/test/org/apache/solr/cloud/FullSolrCloudDistribCmdsTest.java

@@ -467,12 +467,17 @@ public void testThatCantForwardToLeaderFails() throws Exception {
                 (n, c) -> DocCollection.isFullyActive(n, c, 2, 1));
 
         { // HACK: Check the leaderProps for the shard hosted on the node we're going to kill...
-          final Replica leaderProps =
+          List<Replica> replicas =
               cloudClient
                   .getClusterState()
                   .getCollection(collectionName)
-                  .getLeaderReplicas(leaderToPartition.getNodeName())
-                  .get(0);
+                  .getReplicasOnNode(leaderToPartition.getNodeName());
+          assertNotNull(replicas);
+          assertFalse(replicas.isEmpty());
+          List<Replica> leaderReplicas = replicas.stream().filter(Replica::isLeader).toList();
+          assertFalse(leaderReplicas.isEmpty());
+          final Replica leaderProps = leaderReplicas.get(0);
+
           // No point in this test if these aren't true...
           assertNotNull(
               "Sanity check: leaderProps isn't a leader?: " + leaderProps.toString(),

solr/core/src/test/org/apache/solr/update/processor/RoutedAliasUpdateProcessorTest.java

@@ -205,8 +205,10 @@ Set<String> getLeaderCoreNames(ClusterState clusterState) {
         String nodeName = jettySolrRunner.getNodeName();
         String collectionName = core.getCollectionName();
         DocCollection collectionOrNull = clusterState.getCollectionOrNull(collectionName);
-        List<Replica> leaderReplicas = collectionOrNull.getLeaderReplicas(nodeName);
-        if (leaderReplicas != null) {
+        if (collectionOrNull != null) {
+          List<Replica> replicas = collectionOrNull.getReplicasOnNode(nodeName);
+          assertNotNull(replicas);
+          List<Replica> leaderReplicas = replicas.stream().filter(Replica::isLeader).toList();
           for (Replica leaderReplica : leaderReplicas) {
             leaders.add(leaderReplica.getCoreName());
           }

solr/solrj/src/java/org/apache/solr/common/cloud/DocCollection.java

@@ -34,7 +34,6 @@
 import java.util.function.BiConsumer;
 import java.util.function.BiPredicate;
 import java.util.function.Supplier;
-import org.apache.solr.common.cloud.Replica.ReplicaStateProps;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -54,7 +53,6 @@ public class DocCollection extends ZkNodeProps implements Iterable<Slice> {
   private final Map<String, Slice> activeSlices;
   private final Slice[] activeSlicesArr;
   private final Map<String, List<Replica>> nodeNameReplicas;
-  private final Map<String, List<Replica>> nodeNameLeaderReplicas;
   private final DocRouter router;
   private final String znode;
 
@@ -114,7 +112,6 @@ private DocCollection(
     this.configName = (String) props.get(CollectionStateProps.CONFIGNAME);
     this.slices = slices;
     this.activeSlices = new HashMap<>();
-    this.nodeNameLeaderReplicas = new HashMap<>();
     this.nodeNameReplicas = new HashMap<>();
     this.replicationFactor = (Integer) verifyProp(props, CollectionStateProps.REPLICATION_FACTOR);
     this.numReplicas = ReplicaCount.fromProps(props);
@@ -251,15 +248,6 @@ private void addNodeNameReplica(Replica replica) {
       nodeNameReplicas.put(replica.getNodeName(), replicas);
     }
     replicas.add(replica);
-
-    if (replica.getStr(ReplicaStateProps.LEADER) != null) {
-      List<Replica> leaderReplicas = nodeNameLeaderReplicas.get(replica.getNodeName());
-      if (leaderReplicas == null) {
-        leaderReplicas = new ArrayList<>();
-        nodeNameLeaderReplicas.put(replica.getNodeName(), leaderReplicas);
-      }
-      leaderReplicas.add(replica);
-    }
   }
 
   /**
@@ -368,12 +356,6 @@ public List<Replica> getReplicasOnNode(String nodeName) {
     return nodeNameReplicas.get(nodeName);
   }
 
-  /** Get the list of all leaders hosted on the given node or <code>null</code> if none. */
-  @Deprecated
-  public List<Replica> getLeaderReplicas(String nodeName) {
-    return nodeNameLeaderReplicas.get(nodeName);
-  }
-
   public int getZNodeVersion() {
     return znodeVersion;
   }