Handle error in concurrent downsample actions

Author: kkrik-es

muted-tests.yml

@@ -381,9 +381,6 @@ tests:
 - class: org.elasticsearch.xpack.ml.integration.ClassificationIT
   method: testWithOnlyTrainingRowsAndTrainingPercentIsFifty_DependentVariableIsBoolean
   issue: https://github.com/elastic/elasticsearch/issues/121680
-- class: org.elasticsearch.xpack.downsample.DownsampleActionSingleNodeTests
-  method: testDuplicateDownsampleRequest
-  issue: https://github.com/elastic/elasticsearch/issues/122158
 - class: org.elasticsearch.search.SearchCancellationIT
   method: testCancelFailedSearchWhenPartialResultDisallowed
   issue: https://github.com/elastic/elasticsearch/issues/121719

x-pack/plugin/downsample/src/test/java/org/elasticsearch/xpack/downsample/DownsampleActionSingleNodeTests.java

@@ -1760,7 +1760,7 @@ public void testDuplicateDownsampleRequest() throws Exception {
         new Thread(() -> {
             try {
                 downsample(sourceIndex, targetIndex, config);
-            } catch (ResourceAlreadyExistsException e) {
+            } catch (ElasticsearchException e) {
                 firstFailed.set(true);
             } finally {
                 downsampleComplete.countDown();
@@ -1770,7 +1770,7 @@ public void testDuplicateDownsampleRequest() throws Exception {
         new Thread(() -> {
             try {
                 downsample(sourceIndex, targetIndex, config);
-            } catch (ResourceAlreadyExistsException e) {
+            } catch (ElasticsearchException e) {
                 secondFailed.set(true);
             } finally {
                 downsampleComplete.countDown();