What is the reason why docker pull cannot mirror down?

  docker, question
bash-3.2$ docker pull scrapinghub/portia
 Using default tag: latest
 Pulling repository  docker.io/scrapinghub/portia
 5c46b4ea62e2: Layer already being pulled by another client. Waiting.

When there was no response when pull before, control+C was entered.
The mirror source on the daocloud has already been set up

If docker encounters a problem during pull mirroring hang is changed, other pull needs to wait for the unfinished pull to complete before continuing.
So you can restart docker and pull again first.

However, since you have all used the daocloud, you can try his dao pull and this kind of problem will not occur.