It would be helpful if the errors in the log gave more context information about the error. For example, I have this error i found in my app log, but I can't tell what entity this occured on:
May 7 12:10:22.234 - ERROR - Connector: An error has occurred while handling the request. [User 'someone@domain.com' with session id '2734e1b7-a275-4b74-866c-9ada60a87e9b' and roles 'Advance, Admin']
May 7 12:10:22.237 - ERROR - Connector: (1/88) com.mendix.core.CoreRuntimeException: com.mendix.core.CoreRuntimeException: com.mendix.systemwideinterfaces.MendixRuntimeException: com.mendix.core.CoreRuntimeException: Exception occurred in action '{"before":[{}],"action":{"type":"CommitAction"},"after":[{}],"type":"EventExtendedAction"}', all database changes executed by this action were rolled back
May 7 12:10:22.237 - ERROR - Connector: (2/88) #011at com.mendix.basis.actionmanagement.ActionManager.executeInTransactionSync(ActionManager.java:145)
May 7 12:10:22.237 - ERROR - Connector: (3/88)
May 7 12:10:22.237 - ERROR - Connector: (4/88) Caused by: com.mendix.core.CoreRuntimeException: com.mendix.systemwideinterfaces.MendixRuntimeException: com.mendix.core.CoreRuntimeException: Exception occurred in action '{"before":[{}],"action":{"type":"CommitAction"},"after":[{}],"type":"EventExtendedAction"}', all database changes executed by this action were rolled back
May 7 12:10:22.237 - ERROR - Connector: (5/88) #011at com.mendix.basis.actionmanagement.ActionManager.executeSync(ActionManager.java:178)
May 7 12:10:22.237 - ERROR - Connector: (6/88)
May 7 12:10:22.237 - ERROR - Connector: (7/88) Caused by: com.mendix.systemwideinterfaces.MendixRuntimeException: com.mendix.core.CoreRuntimeException: Exception occurred in action '{"before":[{}],"action":{"type":"CommitAction"},"after":[{}],"type":"EventExtendedAction"}', all database changes executed by this action were rolled back
May 7 12:10:22.237 - ERROR - Connector: (8/88) #011at com.mendix.util.classloading.Runner.doRunUsingClassLoaderOf(Runner.java:37)
May 7 12:10:22.237 - ERROR - Connector: (9/88)
May 7 12:10:22.237 - ERROR - Connector: (10/88) Caused by: com.mendix.core.CoreRuntimeException: Exception occurred in action '{"before":[{}],"action":{"type":"CommitAction"},"after":[{}],"type":"EventExtendedAction"}', all database changes executed by this action were rolled back
May 7 12:10:22.237 - ERROR - Connector: (11/88) #011at com.mendix.basis.actionmanagement.CoreActionHandlerImpl.processErrorState(CoreActionHandlerImpl.scala:152)
May 7 12:10:22.237 - ERROR - Connector: (12/88)
May 7 12:10:22.237 - ERROR - Connector: (13/88) Caused by: com.mendix.core.CoreException: com.mendix.core.CoreRuntimeException: com.mendix.systemwideinterfaces.MendixRuntimeException: com.mendix.datastorage.UniqueConstraintViolationException: Duplicate column value violates its unique constraint: Exception occurred while inserting data. (SQL State: 23505, Error Code: 0)
May 7 12:10:22.237 - ERROR - Connector: (14/88) #011at com.mendix.basis.actionmanagement.SyncEventExtendedAction.executeAction(SyncEventExtendedAction.java:43)
May 7 12:10:22.237 - ERROR - Connector: (15/88)
May 7 12:10:22.237 - ERROR - Connector: (16/88) Caused by: com.mendix.core.CoreRuntimeException: com.mendix.systemwideinterfaces.MendixRuntimeException: com.mendix.datastorage.UniqueConstraintViolationException: Duplicate column value violates its unique constraint: Exception occurred while inserting data. (SQL State: 23505, Error Code: 0)
May 7 12:10:22.237 - ERROR - Connector: (17/88) #011at com.mendix.basis.actionmanagement.ActionManager.executeSync(ActionManager.java:178)
May 7 12:10:22.237 - ERROR - Connector: (18/88)
May 7 12:10:22.237 - ERROR - Connector: (19/88) Caused by: com.mendix.systemwideinterfaces.MendixRuntimeException: com.mendix.datastorage.UniqueConstraintViolationException: Duplicate column value violates its unique constraint: Exception occurred while inserting data. (SQL State: 23505, Error Code: 0)
May 7 12:10:22.237 - ERROR - Connector: (20/88) #011at com.mendix.util.classloading.Runner.doRunUsingClassLoaderOf(Runner.java:37)
May 7 12:10:22.237 - ERROR - Connector: (21/88)
May 7 12:10:22.237 - ERROR - Connector: (22/88) Caused by: com.mendix.datastorage.UniqueConstraintViolationException: Duplicate column value violates its unique constraint: Exception occurred while inserting data. (SQL State: 23505, Error Code: 0)
May 7 12:10:22.237 - ERROR - Connector: (23/88) #011at com.mendix.connectionbus.connections.jdbc.JdbcDataStore.getCorrectException(JdbcDataStore.java:1240)
May 7 12:10:22.237 - ERROR - Connector: (24/88) #011at com.mendix.connectionbus.connections.jdbc.JdbcDataStore.execCreateQueries(JdbcDataStore.java:552)
May 7 12:10:22.237 - ERROR - Connector: (25/88) #011at com.mendix.connectionbus.connections.jdbc.JdbcDataStore.store(JdbcDataStore.java:501)
May 7 12:10:22.237 - ERROR - Connector: (26/88) #011at com.mendix.connectionbus.store.EntityStorer.storeDataSetInstance(EntityStorer.java:250)
May 7 12:10:22.237 - ERROR - Connector: (27/88) #011at com.mendix.connectionbus.store.EntityStorer.handleCreateRequest(EntityStorer.java:202)
May 7 12:10:22.237 - ERROR - Connector: (28/88) #011at com.mendix.connectionbus.store.EntityStorer.handleRequest(EntityStorer.java:140)
May 7 12:10:22.237 - ERROR - Connector: (29/88) #011at com.mendix.connectionbus.store.EntityStorer.store(EntityStorer.java:69)
May 7 12:10:22.237 - ERROR - Connector: (30/88) #011at com.mendix.connectionbus.RequestAnalyzer.doRequest(RequestAnalyzer.java:70)
May 7 12:10:22.237 - ERROR - Connector: (31/88) #011at com.mendix.connectionbus.ConnectionBusImpl.doRequest(ConnectionBusImpl.java:478)
May 7 12:10:22.237 - ERROR - Connector: (32/88) #011at com.mendix.basis.action.user.CommitAction.commit(CommitAction.scala:75)
May 7 12:10:22.237 - ERROR - Connector: (33/88) #011at com.mendix.basis.action.user.CommitAction.commitPersistableObjects(CommitAction.scala:65)
May 7 12:10:22.237 - ERROR - Connector: (34/88) #011at com.mendix.basis.action.user.CommitAction.executeAction(CommitAction.scala:44)
May 7 12:10:22.237 - ERROR - Connector: (35/88) #011at com.mendix.basis.action.user.CommitAction.executeAction(CommitAction.scala:21)
May 7 12:10:22.237 - ERROR - Connector: (36/88) #011at com.mendix.systemwideinterfaces.core.UserAction.execute(UserAction.java:50)
May 7 12:10:22.237 - ERROR - Connector: (37/88) #011at com.mendix.basis.actionmanagement.CoreActionHandlerImpl.doCall(CoreActionHandlerImpl.scala:73)
May 7 12:10:22.237 - ERROR - Connector: (38/88) #011at com.mendix.basis.actionmanagement.CoreActionHandlerImpl.call(CoreActionHandlerImpl.scala:53)
May 7 12:10:22.237 - ERROR - Connector: (39/88) #011at com.mendix.core.actionmanagement.CoreAction.call(CoreAction.java:51)
May 7 12:10:22.237 - ERROR - Connector: (40/88) #011at com.mendix.basis.actionmanagement.ActionManager$1.execute(ActionManager.java:170)
May 7 12:10:22.237 - ERROR - Connector: (41/88) #011at com.mendix.util.classloading.Runner.doRunUsingClassLoaderOf(Runner.java:33)
May 7 12:10:22.237 - ERROR - Connector: (42/88) #011at com.mendix.basis.actionmanagement.ActionManager.executeSync(ActionManager.java:174)
May 7 12:10:22.237 - ERROR - Connector: (43/88) #011at com.mendix.basis.actionmanagement.SyncEventExtendedAction.executeAction(SyncEventExtendedAction.java:41)
May 7 12:10:22.237 - ERROR - Connector: (44/88) #011at com.mendix.basis.actionmanagement.EventExtendedAction.execute(EventExtendedAction.java:89)
May 7 12:10:22.237 - ERROR - Connector: (45/88) #011at com.mendix.basis.actionmanagement.CoreActionHandlerImpl.doCall(CoreActionHandlerImpl.scala:73)
May 7 12:10:22.237 - ERROR - Connector: (46/88) #011at com.mendix.basis.actionmanagement.CoreActionHandlerImpl.call(CoreActionHandlerImpl.scala:53)
May 7 12:10:22.237 - ERROR - Connector: (47/88) #011at com.mendix.core.actionmanagement.CoreAction.call(CoreAction.java:51)
May 7 12:10:22.237 - ERROR - Connector: (48/88) #011at com.mendix.basis.actionmanagement.ActionManager$1.execute(ActionManager.java:172)
May 7 12:10:22.237 - ERROR - Connector: (49/88) #011at com.mendix.util.classloading.Runner.doRunUsingClassLoaderOf(Runner.java:33)
May 7 12:10:22.237 - ERROR - Connector: (50/88) #011at com.mendix.basis.actionmanagement.ActionManager.executeSync(ActionManager.java:174)
May 7 12:10:22.237 - ERROR - Connector: (51/88) #011at com.mendix.basis.actionmanagement.ActionManager.executeInTransactionSync(ActionManager.java:138)
May 7 12:10:22.237 - ERROR - Connector: (52/88) #011at com.mendix.basis.component.InternalCore.commit(InternalCore.java:303)
May 7 12:10:22.237 - ERROR - Connector: (53/88) #011at com.mendix.basis.component.InternalCore.commit(InternalCore.java:188)
May 7 12:10:22.237 - ERROR - Connector: (54/88) #011at com.mendix.basis.component.InternalCore.commit(InternalCore.java:157)
May 7 12:10:22.237 - ERROR - Connector: (55/88) #011at com.mendix.webui.actions.client.CommitAction.execute(CommitAction.scala:39)
May 7 12:10:22.237 - ERROR - Connector: (56/88) #011at com.mendix.webui.requesthandling.ClientRequestHandler$$anonfun$handleRequest$1.apply$mcV$sp(ClientRequestHandler.scala:307)
May 7 12:10:22.237 - ERROR - Connector: (57/88) #011at com.mendix.webui.requesthandling.ClientRequestHandler$$anonfun$handleRequest$1.apply(ClientRequestHandler.scala:293)
May 7 12:10:22.237 - ERROR - Connector: (58/88) #011at com.mendix.webui.requesthandling.ClientRequestHandler$$anonfun$handleRequest$1.apply(ClientRequestHandler.scala:293)
May 7 12:10:22.237 - ERROR - Connector: (59/88) #011at com.mendix.basis.actionmanagement.IMonitoredAction$$anon$1.execute(IMonitoredAction.scala:47)
May 7 12:10:22.237 - ERROR - Connector: (60/88) #011at com.mendix.util.classloading.Runner.doRunUsingClassLoaderOf(Runner.java:33)
May 7 12:10:22.237 - ERROR - Connector: (61/88) #011at com.mendix.basis.actionmanagement.IMonitoredAction$class.monitor(IMonitoredAction.scala:49)
May 7 12:10:22.237 - ERROR - Connector: (62/88) #011at com.mendix.webui.requesthandling.ClientRequestHandler$ClientMonitoredAction.monitor(ClientRequestHandler.scala:408)
May 7 12:10:22.237 - ERROR - Connector: (63/88) #011at com.mendix.webui.requesthandling.ClientRequestHandler.handleRequest(ClientRequestHandler.scala:293)
May 7 12:10:22.237 - ERROR - Connector: (64/88) #011at com.mendix.webui.requesthandling.ClientRequestHandler.handleActionWithSessionRequired(ClientRequestHandler.scala:235)
May 7 12:10:22.237 - ERROR - Connector: (65/88) #011at com.mendix.webui.requesthandling.ClientRequestHandler.handleAction(ClientRequestHandler.scala:202)
May 7 12:10:22.237 - ERROR - Connector: (66/88) #011at com.mendix.webui.requesthandling.ClientRequestHandler.liftedTree1$1(ClientRequestHandler.scala:101)
May 7 12:10:22.237 - ERROR - Connector: (67/88) #011at com.mendix.webui.requesthandling.ClientRequestHandler.processRequest(ClientRequestHandler.scala:93)
May 7 12:10:22.237 - ERROR - Connector: (68/88) #011at com.mendix.externalinterface.connector.RequestHandler.doProcessRequest(RequestHandler.java:40)
May 7 12:10:22.237 - ERROR - Connector: (69/88) #011at com.mendix.external.connector.MxRuntimeConnector$1.execute(MxRuntimeConnector.java:70)
May 7 12:10:22.237 - ERROR - Connector: (70/88) #011at com.mendix.external.connector.MxRuntimeConnector$1.execute(MxRuntimeConnector.java:67)
May 7 12:10:22.237 - ERROR - Connector: (71/88) #011at com.mendix.util.classloading.Runner.doRunUsingClassLoaderOf(Runner.java:33)
May 7 12:10:22.237 - ERROR - Connector: (72/88) #011at com.mendix.external.connector.MxRuntimeConnector.processRequest(MxRuntimeConnector.java:73)
May 7 12:10:22.237 - ERROR - Connector: (73/88) #011at com.mendix.basis.impl.MxRuntimeImpl.processRequest(MxRuntimeImpl.java:885)
May 7 12:10:22.237 - ERROR - Connector: (74/88) #011at com.mendix.m2ee.appcontainer.server.handler.RuntimeHandler.handle(RuntimeHandler.java:41)
May 7 12:10:22.237 - ERROR - Connector: (75/88) #011at org.eclipse.jetty.server.handler.HandlerList.handle(HandlerList.java:52)
May 7 12:10:22.237 - ERROR - Connector: (76/88) #011at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:116)
May 7 12:10:22.237 - ERROR - Connector: (77/88) #011at org.eclipse.jetty.server.Server.handle(Server.java:368)
May 7 12:10:22.237 - ERROR - Connector: (78/88) #011at org.eclipse.jetty.server.AbstractHttpConnection.handleRequest(AbstractHttpConnection.java:489)
May 7 12:10:22.237 - ERROR - Connector: (79/88) #011at org.eclipse.jetty.server.AbstractHttpConnection.content(AbstractHttpConnection.java:953)
May 7 12:10:22.237 - ERROR - Connector: (80/88) #011at org.eclipse.jetty.server.AbstractHttpConnection$RequestHandler.content(AbstractHttpConnection.java:1014)
May 7 12:10:22.237 - ERROR - Connector: (81/88) #011at org.eclipse.jetty.http.HttpParser.parseNext(HttpParser.java:861)
May 7 12:10:22.237 - ERROR - Connector: (82/88) #011at org.eclipse.jetty.http.HttpParser.parseAvailable(HttpParser.java:240)
May 7 12:10:22.237 - ERROR - Connector: (83/88) #011at org.eclipse.jetty.server.AsyncHttpConnection.handle(AsyncHttpConnection.java:82)
May 7 12:10:22.237 - ERROR - Connector: (84/88) #011at org.eclipse.jetty.io.nio.SelectChannelEndPoint.handle(SelectChannelEndPoint.java:628)
May 7 12:10:22.237 - ERROR - Connector: (85/88) #011at org.eclipse.jetty.io.nio.SelectChannelEndPoint$1.run(SelectChannelEndPoint.java:52)
May 7 12:10:22.237 - ERROR - Connector: (86/88) #011at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:608)
May 7 12:10:22.237 - ERROR - Connector: (87/88) #011at org.eclipse.jetty.util.thread.QueuedThreadPool$3.run(QueuedThreadPool.java:543)
May 7 12:10:22.237 - ERROR - Connector: (88/88) #011at java.lang.Thread.run(Thread.java:745)