spotify/docker-client

docker.pull("imagename") causes docker daemon to pull all known tags of the image

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#873 opened on Aug 24, 2017

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Description

As seen in https://github.com/spotify/docker-client/issues/857#issuecomment-324380422, pulling the name of an image repository without specifying a tag (such as dockerClient.pull("redis")) causes the docker daemon to pull all the tags that it can find of that image.

When dockerClient.pull("redis") is called, the client sends a request to the Docker Remote API like POST /images/create?fromImage=redis.

When no tag parameter is specified for the image pull/create, it seems like the daemon will try to pull all known tags from the repository, which appears to be behavior that isn't quite documented (but then again it is not clear which image should be pulled for this request).

When you do docker pull redis from the command line, the docker-cli sends the request POST /images/create?fromImage=redis&tag=latest - it interprets the tag-less image request as being :latest implicitly, but our DockerClient doesn't do the same.

It would probably make more sense for DefaultDockerClient to quietly interpret an image pull like "redis" as "redis:latest" to behave the same as docker pull, rather than sending POST /images/create?fromImage=redis to pull all known tags.

Contributor guide

Tech stack
java
Domain
backendapi
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
under 1 hour
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
JavaDocker
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
70
Research direction
The fix likely involves modifying the default pull method in DefaultDockerClient to default the tag to 'latest' when none is specified. The issue references a related comment in #857 and discusses the Docker API behavior. Look at the pull method implementation and add logic similar to the docker cli's implicit tag handling.