[KAFKA-7344] Return early when all tasks are assigned in StickyTaskAssignor#assignActive

• Type: Improvement
• Status: Open
• Priority: Minor
• Resolution: Unresolved
• Component/s: streams
• Labels: optimization
• Assignee: kevin.chen
• Reporter: Ted Yu
• Created: 26/Aug/18 00:52
• Updated: 16/Sep/18 18:12

Description

After re-assigning existing active tasks to clients that previously had the same active task, there is chance that taskIds.size() == assigned.size(), i.e. all tasks are assigned .
The method continues with:

        final Set<TaskId> unassigned = new HashSet<>(taskIds);
        unassigned.removeAll(assigned);

We can check the above condition and return early before allocating HashSet.

Similar optimization can be done before the following (around line 112):

        // assign any remaining unassigned tasks
        final List<TaskId> sortedTasks = new ArrayList<>(unassigned);