Why a cancelled task is still on the list?

Elastic Stack Elasticsearch
1

Hello, elastic!

While running multiple msearch API through Java clients, I found one of the tasks took abnormally long.
So I executed Task Cancel API, but it doesn't seem cleanup properly.
When I check the task via Task API, it shows cancelled: true, cancellable: true, completed: false and running time is still increasing.
I know it doesn't work right away, however, it has been almost a day.
Now, I need to figure it out what should I do in this situation.

My question is:

  1. Why cancelled task (cancelled: true) is still on the list? Do I need to keep waiting?
  2. What could be the solution for this situation? delete the task forcibly? reboot server? force merge? etc
  3. Does DELETE .tasks/task/_doc/<yourtaskid> delete a specific task? and is there no side effects?
    (How to delete a task in Elasticsearch v7.14 - #7 by stephenb)
  4. Is there anything more I can check?

Thank you in advance!

2

Hello,

What is your Elasticsearch version? You didn't mention it.

3

sorry for that. It is 7.10!

4

7.10 is pretty old and no more supported.

I don't think that there is much that you can do, I would suggest that you try to restart the node where the task is running to see if this solve this issue.

5

You should also upgrade.

6

Is there any solution if I upgrade to 8.8 and face the same problem?

7

I think this is a bug. Possibly it's been fixed already in the couple of years since 7.10 was released, but if you can reproduce it in a supported version then I would like to investigate further.

9

Unfortunately, it is barely possible to upgrade the current version in my situation.

Anyway..
After rebooting the nodes, the deadlock task on the list has been removed for now.
I will let you know, when I face the same problem again.

Thanks for helping!