[ML] Warn for model load failures if they have a status code <500 (#113280) (#113381)

* On model load failure, warn if the failure status code was less tahn 500

* Update docs/changelog/113280.yaml

Author: maxhniebergall

docs/changelog/113280.yaml

@@ -0,0 +1,5 @@
+pr: 113280
+summary: Warn for model load failures if they have a status code <500
+area: Machine Learning
+type: bug
+issues: []

x-pack/plugin/ml/src/main/java/org/elasticsearch/xpack/ml/inference/assignment/TrainedModelAssignmentNodeService.java

@@ -9,6 +9,7 @@
 
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
+import org.elasticsearch.ElasticsearchException;
 import org.elasticsearch.ResourceNotFoundException;
 import org.elasticsearch.action.ActionListener;
 import org.elasticsearch.action.search.SearchPhaseExecutionException;
@@ -775,7 +776,11 @@ private void updateStoredState(String deploymentId, RoutingInfoUpdate update, Ac
     }
 
     private void handleLoadFailure(TrainedModelDeploymentTask task, Exception ex, ActionListener<Boolean> retryListener) {
-        logger.error(() -> "[" + task.getDeploymentId() + "] model [" + task.getParams().getModelId() + "] failed to load", ex);
+        if (ex instanceof ElasticsearchException esEx && esEx.status().getStatus() < 500) {
+            logger.warn(() -> "[" + task.getDeploymentId() + "] model [" + task.getParams().getModelId() + "] failed to load", ex);
+        } else {
+            logger.error(() -> "[" + task.getDeploymentId() + "] model [" + task.getParams().getModelId() + "] failed to load", ex);
+        }
         if (task.isStopped()) {
             logger.debug(
                 () -> format(