o1 qsize: 6
received: a
o1 qsize: 5
from o1: b
from o1: c
from o1: d
from o1: e
from o1: f
no more o1
o1 qsize: 0
o2 returned: 11
o2 returned: 22
o2 returned: 33
o2 returned: 44
o2 returned: 55
o2 returned: 66
o2 returned: 77
o2 returned: 88
o2 returned: 99
drain: qsize 5
drain: 1
drain: 2
drain: 3
drain: 4
drain: 5
drain: qsize 0
drain: destroying op
done
