Doubled tasks in Activiti process - apache-camel

Question

I've got an Activiti code (Activiti 5.19 run with Camel on Servicemix) running in production and face some peculiar problem: sometimes I've got cases of doubled tasks in an execution (one of them is even tripled). It seems to have no clear pattern. What I've tested my code would throw an exception if any javascript call service to close the same task twice for some reason.
The doubled tasks neither can be completed (resulting "UserTask should not be signalled before complete" exception) nor deleted because the tasks are part of the running execution.
I cannot figure out what could cause such an effect and how to get rid of the redundant tasks in order to finish the damaged processes.
Is there possible to just delete the later records (with the highest task id) in the act_ru_task?
Anybody could help?
<?xml version="1.0" encoding="UTF-8"?>
<definitions xmlns="http://www.omg.org/spec/BPMN/20100524/MODEL"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema"
xmlns:activiti="http://activiti.org/bpmn" xmlns:bpmndi="http://www.omg.org/spec/BPMN/20100524/DI"
xmlns:omgdc="http://www.omg.org/spec/DD/20100524/DC" xmlns:omgdi="http://www.omg.org/spec/DD/20100524/DI"
typeLanguage="http://www.w3.org/2001/XMLSchema" expressionLanguage="http://www.w3.org/1999/XPath"
targetNamespace="http://www.activiti.org/test">
<collaboration id="Collaboration">
<participant id="pool1" name="Pool" processRef="process_pool1"></participant>
</collaboration>
<process id="new_marketing" name="marketing" isExecutable="true" activiti:candidateStarterGroups="marketing,task_manager">
<laneSet id="laneSet_new_marketing">
<lane id="lane1" name="marketing">
<flowNodeRef>usertask1</flowNodeRef>
<flowNodeRef>startevent1</flowNodeRef>
<flowNodeRef>exclusivegateway1</flowNodeRef>
<flowNodeRef>usertask2</flowNodeRef>
<flowNodeRef>usertask3</flowNodeRef>
<flowNodeRef>usertask4</flowNodeRef>
<flowNodeRef>endevent1</flowNodeRef>
<flowNodeRef>exclusivegateway2</flowNodeRef>
<flowNodeRef>exclusivegateway3</flowNodeRef>
<flowNodeRef>usertask5</flowNodeRef>
<flowNodeRef>usertask6</flowNodeRef>
<flowNodeRef>endevent2</flowNodeRef>
</lane>
</laneSet>
<startEvent id="startevent1" name="Start"></startEvent>
<userTask id="usertask1" name="Status_0" activiti:assignee="${employeeName}" activiti:candidateGroups="marketing" activiti:dueDate="${dueDate}">
<extensionElements>
<activiti:formProperty id="actionsForm" name="actions" type="enum" writable="false">
<activiti:value id="cancel" name="cancel"></activiti:value>
<activiti:value id="accepted" name="accepted"></activiti:value>
<activiti:value id="wait" name="wait"></activiti:value>
</activiti:formProperty>
</extensionElements>
</userTask>
<sequenceFlow id="flow12" sourceRef="startevent1" targetRef="usertask1"></sequenceFlow>
<exclusiveGateway id="exclusivegateway1" name="Exclusive Gateway"></exclusiveGateway>
<sequenceFlow id="flow1" sourceRef="usertask1" targetRef="exclusivegateway1"></sequenceFlow>
<userTask id="usertask2" name="Status_10" activiti:assignee="${employeeName}">
<extensionElements>
<activiti:formProperty id="actionsForm" name="actions" type="enum" writable="false">
<activiti:value id="cancel" name="cancel"></activiti:value>
<activiti:value id="proceed" name="proceed"></activiti:value>
<activiti:value id="application" name="application"></activiti:value>
<activiti:value id="accepted" name="accepted"></activiti:value>
<activiti:value id="wait" name="wait"></activiti:value>
</activiti:formProperty>
</extensionElements>
</userTask>
<sequenceFlow id="flow2" sourceRef="exclusivegateway1" targetRef="usertask2">
<conditionExpression xsi:type="tFormalExpression"><![CDATA[${action == 'accepted'}]]></conditionExpression>
</sequenceFlow>
<userTask id="usertask3" name="Status_1" activiti:assignee="${employeeName}" activiti:dueDate="${dueDate}"></userTask>
<sequenceFlow id="flow3" name="Wait" sourceRef="exclusivegateway1" targetRef="usertask3">
<conditionExpression xsi:type="tFormalExpression"><![CDATA[${action == 'wait'}]]></conditionExpression>
</sequenceFlow>
<sequenceFlow id="flow4" sourceRef="usertask3" targetRef="usertask1"></sequenceFlow>
<userTask id="usertask4" name="Status_1000" activiti:assignee="${employeeName}"></userTask>
<sequenceFlow id="flow5" name="GiveUp" sourceRef="exclusivegateway1" targetRef="usertask4">
<conditionExpression xsi:type="tFormalExpression"><![CDATA[${action == 'cancel'}]]></conditionExpression>
</sequenceFlow>
<endEvent id="endevent1" name="End"></endEvent>
<sequenceFlow id="flow6" sourceRef="usertask4" targetRef="endevent1"></sequenceFlow>
<exclusiveGateway id="exclusivegateway2" name="Exclusive Gateway"></exclusiveGateway>
<sequenceFlow id="flow7" sourceRef="usertask2" targetRef="exclusivegateway2"></sequenceFlow>
<endEvent id="endevent2" name="End"></endEvent>
<sequenceFlow id="flow10" sourceRef="exclusivegateway2" targetRef="usertask2">
<conditionExpression xsi:type="tFormalExpression"><![CDATA[${action == 'wait'}]]></conditionExpression>
</sequenceFlow>
<sequenceFlow id="flow11" name="GiveUp" sourceRef="exclusivegateway2" targetRef="usertask4">
<conditionExpression xsi:type="tFormalExpression"><![CDATA[${action == 'cancel'}]]></conditionExpression>
</sequenceFlow>
<sequenceFlow id="flow8" sourceRef="exclusivegateway2" targetRef="usertask5">
<conditionExpression xsi:type="tFormalExpression"><![CDATA[${action == 'application'}]]></conditionExpression>
</sequenceFlow>
<sequenceFlow id="flow13" sourceRef="exclusivegateway2" targetRef="usertask6">
<conditionExpression xsi:type="tFormalExpression"><![CDATA[${action == 'proceed' || action == 'accepted'}]]></conditionExpression>
</sequenceFlow>
<userTask id="usertask5" name="Status_50" activiti:assignee="${employeeName}">
<extensionElements>
<activiti:formProperty id="actionsForm" name="actions" type="enum" writable="false">
<activiti:value id="cancel" name="cancel"></activiti:value>
<activiti:value id="accepted" name="accepted"></activiti:value>
</activiti:formProperty>
</extensionElements>
</userTask>
<sequenceFlow id="flow14" sourceRef="usertask5" targetRef="exclusivegateway3"></sequenceFlow>
<exclusiveGateway id="exclusivegateway3" name="Exclusive Gateway"></exclusiveGateway>
<sequenceFlow id="flow15" sourceRef="exclusivegateway3" targetRef="usertask6">
<conditionExpression xsi:type="tFormalExpression"><![CDATA[${action == 'accepted'}]]></conditionExpression>
</sequenceFlow>
<userTask id="usertask6" name="Status_90" activiti:assignee="${employeeName}"></userTask>
<sequenceFlow id="flow17" sourceRef="usertask6" targetRef="endevent2">
<conditionExpression xsi:type="tFormalExpression"><![CDATA[${action == 'accepted'}]]></conditionExpression>
</sequenceFlow>
<sequenceFlow id="flow16" sourceRef="exclusivegateway3" targetRef="usertask4">
<conditionExpression xsi:type="tFormalExpression"><![CDATA[${action == 'cancel'}]]></conditionExpression>
</sequenceFlow>
</process>
</definitions>
The problem was checked in Activiti database using the following query:
select * from act_ru_task t0 where t0.execution_id_ in (select id_ from act_ru_execution t1 where (select count(*) from act_ru_task t2 where t1.id_ = t2.execution_id_) > 1);
Query presented 30 cases like this, below 3 of them (user logins anonimised):
id_ | rev_ | execution_id_ | proc_inst_id_ | proc_def_id_ | name_ | parent_task_id_ | description_ | task_def_key_ | owner_ | assignee_ |delegation_ | priority_ | create_time_ |
118399 | 1 | 118373 | 118373 | new_marketing:3:5004 | Status_50 | | | usertask5 | | auser | | 50 | 2017-08-08 08:46:28.771 |
118396 | 1 | 118373 | 118373 | new_marketing:3:5004 | Status_50 | | | usertask5 | | auser | | 50 | 2017-08-08 08:46:28.769 |
634792 | 1 | 453636 | 453636 | new_marketing:3:5004 | Status_1000 | | | usertask4 | | buser | | 50 | 2018-04-04 09:49:13.853 |
634791 | 1 | 453636 | 453636 | new_marketing:3:5004 | Status_1000 | | | usertask4 | | buser | | 50 | 2018-04-04 09:49:13.853 |
527864 | 1 | 527837 | 527837 | new_marketing:3:5004 | Status_90 | | | usertask6 | | cuser | | 50 | 2018-02-01 16:06:56.089 |
527867 | 1 | 527837 | 527837 | new_marketing:3:5004 | Status_90 | | | usertask6 | | cuser | | 50 | 2018-02-01 16:06:56.092 |