Fix flaky test by preventing duplicate keys in random mapping fields (o…

…pensearch-project#9184)

* Prevent duplicate keys in random mapping fields

Signed-off-by: Daniel Widdis <widdis@gmail.com>

* Aliases were already unique. Used while loop for indices to keep size

Signed-off-by: Daniel Widdis <widdis@gmail.com>

---------

Signed-off-by: Daniel Widdis <widdis@gmail.com>
Signed-off-by: Kiran Reddy <kkreddy@amazon.com>

test/framework/src/main/java/org/opensearch/index/RandomCreateIndexGenerator.java

@@ -40,6 +40,8 @@
 import org.opensearch.core.xcontent.XContentBuilder;
 
 import java.io.IOException;
+import java.util.HashSet;
+import java.util.Set;
 
 import static org.opensearch.cluster.metadata.IndexMetadata.SETTING_NUMBER_OF_REPLICAS;
 import static org.opensearch.cluster.metadata.IndexMetadata.SETTING_NUMBER_OF_SHARDS;
@@ -112,8 +114,12 @@ public static void randomMappingFields(XContentBuilder builder, boolean allowObj
         builder.startObject("properties");
 
         int fieldsNo = randomIntBetween(0, 5);
-        for (int i = 0; i < fieldsNo; i++) {
-            builder.startObject(randomAlphaOfLength(5));
+        Set<String> uniqueFields = new HashSet<>();
+        while (uniqueFields.size() < fieldsNo) {
+            uniqueFields.add(randomAlphaOfLength(5));
+        }
+        for (String uniqueField : uniqueFields) {
+            builder.startObject(uniqueField);
 
             if (allowObjectField && randomBoolean()) {
                 randomMappingFields(builder, false);