GoogleContainerTools/skaffold

feature request: more control over the docker build context

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#2,110 opened on May 10, 2019

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area/buildhelp wantedkind/feature-requestneeds-design-proposalplatform/monorepopriority/p3

Description

I have a monorepo with shared code. Because docker doesn't follow symlinks and never will, I have to copy that shared code into the right place before building the image for each service. There's currently no facility for doing that with skaffold. I'm using VSCode's Cloud Code extension, so running a wrapper script isn't straightforward, but in any case, I'd like the build to be fully described in the definition, not be dependent on some external glue.

#1441 describes one approach to solving this, which would be great, but I don't need the full flexibility of a custom script.

What I'd like to see is the ability to control which parts of the context are put into the tarball that is sent to Docker. Being able to specify paths, and mappings would be sufficient for my use-case. For example:

context:
  root: .
  paths:
    - mapRef:
        from: services/mercury/src
        to: .
    - mapRef:
        from: shared/nodejs/src
        to: ./lib

This would create a tarball that had files from mercury at the root, and files from the shared source at ./lib. Ideally, it would do this without actually copying the shared files into the mercury service in the local file system.

The absence of the path key would cause behaviour as currently is, i.e. everything beneath the context.

Contributor guide

Tech stack
godocker
Domain
devops
Issue type
feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
4
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
3-5 days
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
GoDocker build contextSkaffold build system
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
20
Research direction
This feature request asks for more control over Docker build context in Skaffold. Currently, Skaffold sends the entire context directory to Docker. The issue proposes a configuration to specify paths and mappings. Related issue #1441 suggests a custom script approach but is not implemented. To implement this, one would need to modify the Docker builder in Skaffold's codebase, likely in the pkg/skaffold/docker package, to support a new context configuration. The implementation should create a tarball with only specified paths, without copying files locally. It would be similar to .dockerignore but more flexible. This is a substantial feature requiring deep understanding of Skaffold's architecture and Docker's build API.
feature request: more control over the docker build context · GoogleContainerTools/skaffold#2110 | Good First Issue