Reduce maximum number of concurrent requests in BulkProcessorIT

The test configuration with seed A23029712A7EFB34 overwhelmed the pool which is invoked
in TransportService#sendLocalRequest().

With this commit we reduce the maximum number of concurrent requests from 10 to 7 and
add the failure message to the test output on the failing assertion for easier analysis.

Author: danielmitterdorfer

core/src/test/java/org/elasticsearch/action/bulk/BulkProcessorIT.java

@@ -105,7 +105,7 @@ public void testBulkProcessorFlush() throws InterruptedException {
     public void testBulkProcessorConcurrentRequests() throws Exception {
         int bulkActions = randomIntBetween(10, 100);
         int numDocs = randomIntBetween(bulkActions, bulkActions + 100);
-        int concurrentRequests = randomIntBetween(0, 10);
+        int concurrentRequests = randomIntBetween(0, 7);
 
         int expectedBulkActions = numDocs / bulkActions;
 
@@ -141,7 +141,7 @@ public void testBulkProcessorConcurrentRequests() throws Exception {
 
         Set<String> ids = new HashSet<>();
         for (BulkItemResponse bulkItemResponse : listener.bulkItems) {
-            assertThat(bulkItemResponse.isFailed(), equalTo(false));
+            assertThat(bulkItemResponse.getFailureMessage(), bulkItemResponse.isFailed(), equalTo(false));
             assertThat(bulkItemResponse.getIndex(), equalTo("test"));
             assertThat(bulkItemResponse.getType(), equalTo("test"));
             //with concurrent requests > 1 we can't rely on the order of the bulk requests