Problem when updating process variables


In our process, we use a lot of json variables. As they are used in the gateways, they have to be set even if they are not actually filled with data (yet). I now run into problems when I try to update them in the course of the process:

 > Object infoJson = runtimeService.getVariable(processInstanceID, "infos");
>         List<Object> infos =  new ObjectMapper().readValue((String) infoJson, List.class);
>         Map<String, String> infoElement = newHashMap();
>         infoElement.put("bugs", 3);
>         infos.add(infoElement);

>         runtimeService.setVariable(processInstanceID, "infos", new ObjectMapper()
>                 .writerWithDefaultPrettyPrinter().writeValueAsString(infos));

The exception I get is:

org.camunda.bpm.engine.ProcessEngineException: ENGINE-03004 Exception while executing Database Operation 'INSERT IdentityLinkEntity[7d18a44c-7dbc-11e7-8e63-7a3a092e9fec]' with message '
### Error updating database.  Cause: com.mysql.jdbc.exceptions.jdbc4.MySQLIntegrityConstraintViolationException: Cannot add or update a child row: a foreign key constraint fails (`bpm_dev_local`.`act_ru_identitylink`, CONSTRAINT `ACT_FK_TSKASS_TASK` FOREIGN KEY (`TASK_ID_`) REFERENCES `ACT_RU_TASK` (`ID_`))
### The error may involve org.camunda.bpm.engine.impl.persistence.entity.IdentityLinkEntity.insertIdentityLink-Inline
### The error occurred while setting parameters
### SQL: insert into ACT_RU_IDENTITYLINK (ID_, TYPE_, USER_ID_, GROUP_ID_, TASK_ID_, PROC_DEF_ID_, TENANT_ID_, REV_ )     values (?,             ?,             ?,             ?,             ?,             ?,             ?,             1            )
### Cause: com.mysql.jdbc.exceptions.jdbc4.MySQLIntegrityConstraintViolationException: Cannot add or update a child row: a foreign key constraint fails (`bpm_dev_local`.`act_ru_identitylink`, CONSTRAINT `ACT_FK_TSKASS_TASK` FOREIGN KEY (`TASK_ID_`) REFERENCES `ACT_RU_TASK` (`ID_`))'. Flush summary: 
  INSERT HistoricVariableInstanceEntity[76b6baff-7dbc-11e7-8e63-7a3a092e9fec]
  INSERT HistoricVariableInstanceEntity[76b6bb00-7dbc-11e7-8e63-7a3a092e9fec]
  INSERT HistoricVariableInstanceEntity[76b6e211-7dbc-11e7-8e63-7a3a092e9fec]
  INSERT HistoricVariableInstanceEntity[77a783a5-7dbc-11e7-8e63-7a3a092e9fec]
  INSERT HistoricVariableInstanceEntity[77a783a6-7dbc-11e7-8e63-7a3a092e9fec]
  INSERT HistoricVariableInstanceEntity[7d165a57-7dbc-11e7-8e63-7a3a092e9fec]
  INSERT HistoricTaskInstanceEventEntity[7d18a44b-7dbc-11e7-8e63-7a3a092e9fec]
  INSERT HistoricProcessInstanceEventEntity[76b693ed-7dbc-11e7-8e63-7a3a092e9fec]
  INSERT HistoricActivityInstanceEventEntity[EndEvent_0x3qy79:7d19197d-7dbc-11e7-8e63-7a3a092e9fec]
  INSERT HistoricActivityInstanceEventEntity[StartEvent_Main:76b6e213-7dbc-11e7-8e63-7a3a092e9fec]
  INSERT HistoricActivityInstanceEventEntity[Task_14bg7eu:76b6e214-7dbc-11e7-8e63-7a3a092e9fec]
  INSERT HistoricActivityInstanceEventEntity[register_form:7d187d3a-7dbc-11e7-8e63-7a3a092e9fec]
  INSERT IdentityLinkEntity[7d18a44c-7dbc-11e7-8e63-7a3a092e9fec]
	at org.camunda.bpm.engine.impl.db.EnginePersistenceLogger.flushDbOperationException(
	at org.camunda.bpm.engine.impl.db.entitymanager.DbEntityManager.flushDbOperationManager(
	at org.camunda.bpm.engine.impl.db.entitymanager.DbEntityManager.flush(
	at org.camunda.bpm.engine.impl.interceptor.CommandContext.flushSessions(
	at org.camunda.bpm.engine.impl.interceptor.CommandContext.close(
	at org.camunda.bpm.engine.impl.interceptor.CommandContextInterceptor.execute(
	at org.camunda.bpm.engine.spring.SpringTransactionInterceptor$1.doInTransaction(
	at org.camunda.bpm.engine.spring.SpringTransactionInterceptor.execute(
	at org.camunda.bpm.engine.impl.interceptor.ProcessApplicationContextInterceptor.execute(
	at org.camunda.bpm.engine.impl.interceptor.LogInterceptor.execute(
	at org.camunda.bpm.engine.impl.ProcessInstantiationBuilderImpl.executeWithVariablesInReturn(
	at org.camunda.bpm.engine.impl.ProcessInstantiationBuilderImpl.execute(
	at org.camunda.bpm.engine.impl.ProcessInstantiationBuilderImpl.execute(
	at org.camunda.bpm.engine.impl.RuntimeServiceImpl.startProcessInstanceByKey(

I am quite new to Camunda, but from the docs it seems that it is pretty normal to update process variables. Indeed, for most of them it works - we even reuse variables during the process for different gateways. Any help would be appreciated!


@auringo have you looked at using SPIN?


Hi Stephen, yes I have looked at it, but we are not using it at the moment. Are you implying that my problem could be related to JSON parsing? As far as I can see, the json is alright and can be parsed (can be checked in the debugger), but the problem happens after that, when saving to the database.



Its not 100% clear to me, however are these process variables persisted as a String rather than Json as a bytearray? If so, could it be that you occasionally exceed the 4k storage limit and thus referential integrity breaks down? Could be a long shot, but something to consider…




The exception does not seem to be directly related to the code you posted. It shows a constraint violation exception that an identity link is inserted that references a non-existing task (e.g. the candidate user relation results in an identity link). Could you please upload a minimal application or unit test to github that reproduces this? You can use the unit testing template to get started: