docker pull wait.kontain.me/some-unique-string enqueues a background task to
generate a random image, which will eventually be served.
By default, the task runs after 10 seconds. You can request the delay time (up to one hour) using the image tag.
After an image is generated for the unique string, it will be served until the image is evicted in the next 24 hours.
Pull a random image available in 10 seconds:
docker pull wait.kontain.me/blah-blah
Pull a random image available in 30 seconds:
docker pull wait.kontain.me/random:30s
This screencast requests an image that should exist in five seconds, then waits to see it appear and checks that it's valid.
This demonstrates being able to asynchronously produce an image, rather than blocking the initial pull HTTP request until the image is available.
A container orchestrator like Kubernetes would pull this image and report
ImagePullBackoff until the image was finally served, at which point it would
pull and run it. In the meantime, the registry could be building or mirroring
or modifying the image in the background.