BRPOPLPUSH is the blocking variant of RPOPLPUSH.
When source contains elements, this command behaves exactly like RPOPLPUSH.
When source is empty, Redis will block the connection until another client
pushes to it or until timeout is reached.
A timeout of zero can be used to block indefinitely.
See RPOPLPUSH for more information.
返回值
Bulk string reply: the element being popped from source and pushed to destination.
If timeout is reached, a Null reply is returned.
Pattern: Reliable queue
Please see the pattern description in the RPOPLPUSH documentation.
Pattern: Circular list
Please see the pattern description in the RPOPLPUSH documentation.