[Backport 2.x] Fix: do not double-wrap OpenSearchException.

CHANGELOG.md

@@ -29,6 +29,7 @@ Inspired from [Keep a Changelog](https://keepachangelog.com/en/1.0.0/)
 ### Fixed
 - Make ChildrenAggregate as a SingleBucketAggregate ([#306](https://github.com/opensearch-project/opensearch-java/pull/306))
 - Fix /_nodes/stats, /_nodes/info throwing serialization error ([#315](https://github.com/opensearch-project/opensearch-java/pull/315))
+- Do not double-wrap OpenSearchException on error ([#323](https://github.com/opensearch-project/opensearch-java/pull/323))
 - Fix AwsSdk2TransportOptions.responseCompression ([#322](https://github.com/opensearch-project/opensearch-java/pull/322))
 
 ### Security

java-client/src/main/java/org/opensearch/client/transport/aws/AwsSdk2Transport.java

@@ -526,6 +526,8 @@ private <ResponseT, ErrorT> ResponseT parseResponse(
                     ErrorT error = errorDeserializer.deserialize(parser, mapper);
                     throw new OpenSearchException((ErrorResponse) error);
                 }
+            } catch (OpenSearchException e) {
+                throw e;
             } catch (Exception e) {
                 // can't parse the error - use a general exception
                 ErrorCause.Builder cause = new ErrorCause.Builder();

java-client/src/test/java/org/opensearch/client/opensearch/integTest/aws/AwsSdk2SearchIT.java

@@ -13,10 +13,13 @@
 import org.opensearch.client.opensearch.OpenSearchAsyncClient;
 import org.opensearch.client.opensearch.OpenSearchClient;
 import org.opensearch.client.opensearch._types.OpType;
+import org.opensearch.client.opensearch._types.OpenSearchException;
 import org.opensearch.client.opensearch._types.Refresh;
 import org.opensearch.client.opensearch.core.IndexRequest;
 import org.opensearch.client.opensearch.core.IndexResponse;
 import org.opensearch.client.opensearch.core.SearchResponse;
+import org.opensearch.client.opensearch.indices.CreateIndexRequest;
+import org.opensearch.client.opensearch.indices.OpenSearchIndicesClient;
 
 import java.util.List;
 import java.util.concurrent.CompletableFuture;
@@ -133,4 +136,18 @@ private CompletableFuture<IndexResponse> addDoc(
             return CompletableFuture.failedFuture(e);
         }
     }
+
+    @Test
+    public void testDoubleWrappedException() throws Exception {
+        // ensure the test index exists
+        resetTestIndex(false);
+        // attempt to create the same index a second time
+        OpenSearchIndicesClient client = getIndexesClient(false, null, null);
+        var req = new CreateIndexRequest.Builder().index(TEST_INDEX);
+        Exception exception = Assert.assertThrows(OpenSearchException.class, () -> {
+            client.create(req.build());
+        });
+        // error message contains the actual error, not a generic [http_exception]
+        Assert.assertTrue(exception.getMessage().contains("[resource_already_exists_exception]"));
+    }
 }