REST API to start a process instance is holding request until process instance is complete

Question

I'm using Activiti version 6.

I created a BPMN process from activiti-app.
Then I want to start that process from activiti-rest.war using the API.

http://localhost:8080/activiti-rest/service/runtime/process-instances

request body :

 {

   "processDefinitionKey":"cep_dispatch_process",
   "businessKey":"myBusinessKey",
     "returnVariables": false
}

header :
Content-Type:application/json

As I see in the LOG process is being started in tomcat threads. referring latest GitHub code:

Activiti-activiti-6.0.0\modules\activiti-rest\src\main\java\org\activiti\rest\service\api\runtime\process\ProcessInstanceCollectionResource.java

When I see method,

@RequestMapping(value = "/runtime/process-instances", method = RequestMethod.POST, produces = "application/json")
  public ProcessInstanceResponse createProcessInstance(@RequestBody ProcessInstanceCreateRequest request, HttpServletRequest httpRequest, HttpServletResponse response) {

I can see process is being started and not waiting for process to complete, HTTP response is 201. I can understand request is not being hold for process instance to complete.

instance = processInstanceBuilder.start();

response.setStatus(HttpStatus.CREATED.value());

Please refer the log snipped below, I can see process is executing in server thread and request is waiting till process completed.

276-DEBUG 17-01-2019 14:12:07,177- (http-nio-8080-exec-3) ExecutionEntityManagerImpl: Child execution Execution[ id '130023' ] - parent '130021' created with parent 130021
241-DEBUG 17-01-2019 14:12:07,178- (http-nio-8080-exec-3) ContinueProcessOperation: Executing boundary event activityBehavior class org.activiti.engine.impl.bpmn.behavior.BoundaryTimerEventActivityBehavior with execution 130023
171-DEBUG 17-01-2019 14:12:07,202- (http-nio-8080-exec-3) ContinueProcessOperation: Executing activityBehavior class org.activiti.engine.impl.bpmn.behavior.SubProcessActivityBehavior on activity 'sid-1A2A8DF5-764A-4960-8E5D-F347DC10207C' with execution 130021
276-DEBUG 17-01-2019 14:12:07,203- (http-nio-8080-exec-3) ExecutionEntityManagerImpl: Child execution Execution[ id '130025' ] - parent '130021' created with parent 130021
63-DEBUG 17-01-2019 14:12:07,203- (http-nio-8080-exec-3) DefaultActivitiEngineAgenda: Operation class org.activiti.engine.impl.agenda.ContinueProcessOperation added to agenda
70-DEBUG 17-01-2019 14:12:07,203- (http-nio-8080-exec-3) CommandInvoker: Executing operation class org.activiti.engine.impl.agenda.ContinueProcessOperation

Request must not wait for process to complete.

How can I solve this, request to start the process must not wait for process-instance to complete.

As you see in the response below:

{"id":"130028",
"url":"http://localhost:8080/activiti-rest/service/runtime/process-instances/130028",
"businessKey":"myBusinessKey",
"suspended":false,
"ended":true,
"processDefinitionId":"cep_dispatch_process:13:125033",
"processDefinitionUrl":"http://localhost:8080/activiti-rest/service/repository/process-definitions/cep_dispatch_process:13:125033"
,"processDefinitionKey":"cep_dispatch_process",
"activityId":null,
"variables":[],
"tenantId":"",
"name":null,
"completed":true
}

API is returning only after process completes, I add delay of 2 min in service task, I can see request will be waiting.

mshutov mshutov · Accepted Answer · 2019-01-21T10:22:18

I'm not a big guru in Activiti but as a simplest solution I can suggest to activate Async executor and use Asynchronous Continuations for your service task. This could solve your problem. Activiti's behaviour is expected because until it has persisted state to DB it can't say for sure that process is created (because transaction could be rolled back due to DB error for example)

REST API to start a process instance is holding request until process instance is complete

1 Answers