[GitHub] [lucene-solr] tflobbe commented on a change in pull request #677: SOLR-13257: support for stable replica routing preferences

[GitBox <gi...@apache.org>]

tflobbe commented on a change in pull request #677: SOLR-13257: support for stable replica routing preferences
URL: https://github.com/apache/lucene-solr/pull/677#discussion_r302296475
 
 

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 File path: solr/core/src/java/org/apache/solr/handler/component/HttpShardHandlerFactory.java
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 @@ -449,9 +556,83 @@ private static boolean hasReplicaType(Object o, String preferred) {
     }
   }
 
+  private final ReplicaListTransformerFactory randomRltFactory = (String configSpec, SolrQueryRequest request,
+      ReplicaListTransformerFactory fallback) -> shufflingReplicaListTransformer;
+  private ReplicaListTransformerFactory stableRltFactory;
+  private ReplicaListTransformerFactory defaultRltFactory;
+
+  /**
+   * Private class responsible for applying pairwise sort based on inherent replica attributes,
+   * and subsequently reordering any equivalent replica sets according to behavior specified
+   * by the baseReplicaListTransformer.
+   */
+  private static final class TopLevelReplicaListTransformer implements ReplicaListTransformer {
+
+    private final NodePreferenceRulesComparator replicaComp;
+    private final ReplicaListTransformer baseReplicaListTransformer;
+
+    public TopLevelReplicaListTransformer(NodePreferenceRulesComparator replicaComp, ReplicaListTransformer baseReplicaListTransformer) {
+      this.replicaComp = replicaComp;
+      this.baseReplicaListTransformer = baseReplicaListTransformer;
+    }
+
+    @Override
+    public void transform(List<?> choices) {
 
 Review comment:
   I may be very wrong here, but I think the output of this method would be the same (or at least the same in practice) if we first run the transformer on all the list (which essentially either shuffles it or uses the new affinity code to define the order) and then run the `choices.sort(replicaComp)`, since this last one is stable, and will maintain the order of equal elements.
   If that's the case, this method could be much simpler, and we don't need to find the boundaries, etc, plus the transformer gets called only once instead of once per group.

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