update error code to 429 for rate limiting and update logs

Signed-off-by: Xun Zhang <xunzh@amazon.com>

Author: Zhangxunmt

plugin/src/main/java/org/opensearch/ml/action/batch/TransportBatchIngestionAction.java

@@ -33,7 +33,6 @@
 import org.opensearch.ml.common.MLTask;
 import org.opensearch.ml.common.MLTaskState;
 import org.opensearch.ml.common.MLTaskType;
-import org.opensearch.ml.common.exception.MLLimitExceededException;
 import org.opensearch.ml.common.transport.batch.MLBatchIngestionAction;
 import org.opensearch.ml.common.transport.batch.MLBatchIngestionInput;
 import org.opensearch.ml.common.transport.batch.MLBatchIngestionRequest;
@@ -146,9 +145,10 @@ protected void createMLTaskandExecute(MLBatchIngestionInput mlBatchIngestionInpu
 
         mlModelManager.checkMaxBatchJobTask(mlTask, ActionListener.wrap(exceedLimits -> {
             if (exceedLimits) {
-                String error = "exceed maximum BATCH_INGEST Task limits";
+                String error =
+                    "Exceeded maximum limit for BATCH_INGEST tasks. To increase the limit, update the plugins.ml_commons.max_batch_ingestion_tasks setting.";
                 log.warn(error + " in task " + mlTask.getTaskId());
-                listener.onFailure(new MLLimitExceededException(error));
+                listener.onFailure(new OpenSearchStatusException(error, RestStatus.TOO_MANY_REQUESTS));
             } else {
                 mlTaskManager.createMLTask(mlTask, ActionListener.wrap(response -> {
                     String taskId = response.getId();

plugin/src/main/java/org/opensearch/ml/task/MLPredictTaskRunner.java

@@ -55,7 +55,6 @@
 import org.opensearch.ml.common.dataset.MLInputDataType;
 import org.opensearch.ml.common.dataset.MLInputDataset;
 import org.opensearch.ml.common.dataset.remote.RemoteInferenceInputDataSet;
-import org.opensearch.ml.common.exception.MLLimitExceededException;
 import org.opensearch.ml.common.input.MLInput;
 import org.opensearch.ml.common.output.MLOutput;
 import org.opensearch.ml.common.output.MLPredictionOutput;
@@ -257,9 +256,10 @@ protected void executeTask(MLPredictionTaskRequest request, ActionListener<MLTas
         if (actionType.equals(ActionType.BATCH_PREDICT)) {
             mlModelManager.checkMaxBatchJobTask(mlTask, ActionListener.wrap(exceedLimits -> {
                 if (exceedLimits) {
-                    String error = "exceed maximum BATCH_PREDICTION Task limits";
+                    String error =
+                        "Exceeded maximum limit for BATCH_PREDICTION tasks. To increase the limit, update the plugins.ml_commons.max_batch_inference_tasks setting.";
                     log.warn(error + " in task " + mlTask.getTaskId());
-                    listener.onFailure(new MLLimitExceededException(error));
+                    listener.onFailure(new OpenSearchStatusException(error, RestStatus.TOO_MANY_REQUESTS));
                 } else {
                     executePredictionByInputDataType(inputDataType, modelId, mlInput, mlTask, functionName, listener);
                 }