fixed concurrency exception when deleting relation

dao/src/main/java/org/thingsboard/server/dao/sql/relation/JpaRelationDao.java

@@ -157,7 +157,11 @@ public class JpaRelationDao extends JpaAbstractDaoListeningExecutorService imple
     private boolean deleteRelationIfExists(RelationCompositeKey key) {
         boolean relationExistsBeforeDelete = relationRepository.existsById(key);
         if (relationExistsBeforeDelete) {
-            relationRepository.deleteById(key);
+            try {
+                relationRepository.deleteById(key);
+            } catch (ConcurrencyFailureException e) {
+                log.debug("[{}] Concurrency exception while deleting relation", key, e);
+            }
         }
         return relationExistsBeforeDelete;
     }

dao/src/test/java/org/thingsboard/server/dao/service/BaseRelationServiceTest.java

@@ -16,6 +16,8 @@
 package org.thingsboard.server.dao.service;
 
 import com.datastax.oss.driver.api.core.uuid.Uuids;
+import com.google.common.util.concurrent.Futures;
+import com.google.common.util.concurrent.ListenableFuture;
 import org.junit.After;
 import org.junit.Assert;
 import org.junit.Before;
@@ -31,6 +33,7 @@ import org.thingsboard.server.common.data.relation.RelationTypeGroup;
 import org.thingsboard.server.common.data.relation.RelationsSearchParameters;
 import org.thingsboard.server.dao.exception.DataValidationException;
 
+import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
 import java.util.concurrent.ExecutionException;
@@ -84,6 +87,23 @@ public abstract class BaseRelationServiceTest extends AbstractServiceTest {
         Assert.assertTrue(relationService.deleteRelationAsync(SYSTEM_TENANT_ID, childId, subChildId, EntityRelation.CONTAINS_TYPE, RelationTypeGroup.COMMON).get());
     }
 
+    @Test
+    public void testDeleteRelationConcurrently() throws ExecutionException, InterruptedException {
+        AssetId parentId = new AssetId(Uuids.timeBased());
+        AssetId childId = new AssetId(Uuids.timeBased());
+
+        EntityRelation relationA = new EntityRelation(parentId, childId, EntityRelation.CONTAINS_TYPE);
+
+        saveRelation(relationA);
+
+        List<ListenableFuture<Boolean>> futures = new ArrayList<>();
+        for (int i = 0; i < 2; i++) {
+            futures.add(relationService.deleteRelationAsync(SYSTEM_TENANT_ID, relationA));
+        }
+        List<Boolean> results = Futures.allAsList(futures).get();
+        Assert.assertTrue(results.contains(true));
+    }
+
     @Test
     public void testDeleteEntityRelations() throws ExecutionException, InterruptedException {
         AssetId parentId = new AssetId(Uuids.timeBased());