Add log message in RestClient for ScatterGatherStrategy map URIs empt…

…y case (#911)

Co-authored-by: Yingjie Bi <[email protected]>

CHANGELOG.md

@@ -14,6 +14,9 @@ and what APIs have changed, if applicable.
 
 ## [Unreleased]
 
+## [29.42.4] - 2023-06-02
+- Add log message in RestClient for ScatterGatherStrategy map URIs empty case
+
 ## [29.42.3] - 2023-05-18
 - Support for UDS sockets for HTTP/1
 - Make ValidationExtensionSchemaTask cacheable
@@ -5472,7 +5475,8 @@ patch operations can re-use these classes for generating patch messages.
 
 ## [0.14.1]
 
-[Unreleased]: https://github.com/linkedin/rest.li/compare/v29.42.3...master
+[Unreleased]: https://github.com/linkedin/rest.li/compare/v29.42.4...master
+[29.42.4]: https://github.com/linkedin/rest.li/compare/v29.42.3...v29.42.4
 [29.42.3]: https://github.com/linkedin/rest.li/compare/v29.42.2...v29.42.3
 [29.42.2]: https://github.com/linkedin/rest.li/compare/v29.42.1...v29.42.2
 [29.42.1]: https://github.com/linkedin/rest.li/compare/v29.42.0...v29.42.1

gradle.properties

@@ -1,4 +1,4 @@
-version=29.42.3
+version=29.42.4
 group=com.linkedin.pegasus
 org.gradle.configureondemand=true
 org.gradle.parallel=true

restli-client/src/main/java/com/linkedin/restli/client/RestClient.java

@@ -81,6 +81,8 @@
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.atomic.AtomicInteger;
 import javax.activation.MimeTypeParseException;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 import static com.linkedin.r2.disruptor.DisruptContext.*;
 
@@ -131,6 +133,7 @@
  * @author Eran Leshem
  */
 public class RestClient implements Client {
+  private static final Logger LOG = LoggerFactory.getLogger(RestClient.class);
   private static final List<ContentType>  DEFAULT_ACCEPT_TYPES = Collections.emptyList();
   private static final ContentType DEFAULT_CONTENT_TYPE = ContentType.JSON;
   private static final Random RANDOM_INSTANCE = new Random();
@@ -1108,6 +1111,9 @@ public void onSuccess(ProtocolVersion protocolVersion)
         if (mappingResults == null || mappingResults.getMappedKeys().isEmpty())
         {
           // Strategy returns null URIMappingResult or empty mapped hosts, assuming no scatter is needed
+          LOG.error("ScatterGatherStrategy cannot map URIs for request: " + request
+              + ", requestContext: " + requestContext
+              + ", ScatterGatherStrategy needScatterGatherStrategy value: " +  strategy.needScatterGather(request));
           callback.onError(new RestLiScatterGatherException("ScatterGatherStrategy cannot map URIs, this should not happen!"));
           return;
         }