private CoordinatorResult<Void, CoordinatorRecord> maybeCompleteJoinElseSchedule(
        ClassicGroup group
    ) {
        String classicGroupJoinKey = classicGroupJoinKey(group.groupId());
        if (group.hasAllMembersJoined()) {
            // All members have joined. Proceed to sync phase.
            return completeClassicGroupJoin(group);
        } else {
            timer.schedule(
                classicGroupJoinKey,
                group.rebalanceTimeoutMs(),
                TimeUnit.MILLISECONDS,
                false,
                () -> completeClassicGroupJoin(group.groupId())
            );
            return EMPTY_RESULT;
        }
    }
Try to complete the join phase. Otherwise, schedule a new join operation.

@param group The group.

@return The coordinator result that will be appended to the log.
group-coordinator/src/main/java/org/apache/kafka/coordinator/group/GroupMetadataManager.java