I use camunda-external-task-client-js to subscribe service task , and now I have a parallel gateway that means I will finish multiple tasks concurrently (by subscribing topic) . I used this event as below:
`
client.on(“complete:success”, function (task) {})
`
to get completed task , but I found that when I finished a task , it will trigger complete event twice and the completed task is the same . So I want to know that why it will trigger twice ? Thank you for your kindly help~
Hey @GaoxiaoyuVV,
can you please provide the code of the external Task? If you don’t get any API-errors (Failed to complete Task: ...), it’s likely you accidentally subscribed to the complete:success event twice 
Firstly , I need say sorry to you and I have solved this problem . This question is related to Subscribe multiple and dynamic topic with camunda-external-task-client-js and as it said , I want to have multiple and dynamic topic , I put the client event in for loop so it was triggered more than once .
But about parallel gateways , I want to still confirm more thing . Blow is my process XML:
There are two ways what I configured :
①Both of task 2 and task 3 I didn’t configure “Asynchronous Continuations” , and I know when in parallel gateways maybe will trigger OptimisticLockingException .
②Both of task 2 and task 3 I configured “Asynchronous Continuations: after” , this time no error happened . But there is no OptimisticLockingException .
So can you give me some guidance and really thank you for your kindly help~