Distinct collaborators receiving the same task

Describe the bug When two collaborators log into the same project they receive the same task Backend indicates an error:

[2021-04-12 22:11:03,640] [tasks.models::set_lock::103] [ERROR] Current number of locks for task 2 is 1, but overlap=1: that's a bug because this task should not be taken in a label stream (task should be locked)

In the user screen that logged last, sometimes, the “Submit” button disappear.

To Reproduce Steps to reproduce the behavior:

1. Create accounts “user1@localhost” and “user2@localhost”
2. Log user1 and create a sample project
3. Import file with multiple tasks
4. Click to label a task with user1
5. Log user2 (using another browser or anonymous session)
6. Click to label a task with user2

Expected behavior Users receiving different tasks each.

Screenshots Click to label

user2 disappearing top toolbar

Environment (please complete the following information):

• OS: Ubuntu 20.04 focal
• Label Studio Version 1.0.1

EDIT Better description to steps to reproduce the issue and possibly related “Submit button disappear” issue reported above and by @bolotyuh

[bolotyuh]

Yep, once I saw this problem, but can’t reproduce it.

When you refresh the page on the same task top toolbar disappearing as I understood it because we already have annotation

[makseq]

@bolotyuh @rodrigocaus The problem is not so trivial as it might seem. When LS generates the next task for the annotator, it must lock this task for a while until the annotator does his job. And this duration is unpredictable: it could be 1 second, 1 minute, 1 hour, etc.

We tried to use task locks and the label stream looks like what you expect: annotators are given different tasks all the time. Although if you try to press Label again, you won’t see unlabeled & locked tasks, because they have been locked by some annotators for several hours in edge cases. And it’s confusing.

So, you can have two fast workarounds:

• Rewrite this line https://github.com/heartexlabs/label-studio/blob/4f3df84fd38872c6a2405a2d8e330076bebf22db/label_studio/projects/api.py#L434 to next_task = not_solved_tasks.order_by('?').first(), this will randomize tasks on the each API call. It solves the problem particularly.

• Create individual tabs for the each annotator and split tasks via filter id ranges.