root: add --registry-mirror flag

[greut]

Fixes #406.

Description

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• Includes unit tests
• Adds integration tests if needed.

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• Unit tests and or integration tests added.

Release Notes

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- --registry-mirror <url> to override the default docker.io registry.

[greut]

Who could give me hand for the integration tests?

[tejal29]

@greut currently our integration tests are not sophisticated :)
Thank you for your contribution!
you can add a test case here to use the flag --registry-mirror https://github.com/GoogleContainerTools/kaniko/blob/master/integration/integration_test.go#L169

[tandeday]

We need this. What is necessary for this to move on?

[cvgw]

Integration tests failure

Building kaniko image
Building cache warmer image
Building onbuild base image
Pushing onbuild base image
Building hardlink base image
Pushing hardlink base image
Building kaniko image using registry-mirror
Building kaniko image using registry-mirror failed: exit status 125unknown flag: --registry-mirror
See 'docker build --help'.

[greut]

@cvgw Indeed, I didn't take the proper time to understand how the integration test where meant to be written. Let me know if makes more sense now.

[cvgw]

This causing the integration tests to fail as the references to dockerfile have not been updated

# github.com/GoogleContainerTools/kaniko/integration [github.com/GoogleContainerTools/kaniko/integration.test]
./integration_test.go:193:10: undefined: dockerfile
./integration_test.go:206:10: undefined: dockerfile
./integration_test.go:248:10: undefined: dockerfile
./integration_test.go:286:2: undefined: dockerfile
./integration_test.go:291:10: undefined: dockerfile

[tejal29]

@tejal29 sorry to confuse the cla bot a bit more.

no worries @greut I will take this home!

[samos123]

Looks good!

[samos123]

Kokoro failure is safe to ignore since Kokoro doesn't use the pull request branch for test cases dockerfiles. See error in kokoro here:

== RUN   TestBuildViaRegistryMirror
--- FAIL: TestBuildViaRegistryMirror (10.54s)
    integration_test.go:296: Failed to build image gcr.io/kaniko-test/docker-dockerfile_registry_mirror with docker command "[docker build -t gcr.io/kaniko-test/docker-dockerfile_registry_mirror -f integration/dockerfiles/Dockerfile_registry_mirror github.com/GoogleContainerTools/kaniko]": exit status 1 unable to prepare context: unable to evaluate symlinks in Dockerfile path: lstat /tmpfs/tmp/docker-build-git816172650/integration/dockerfiles/Dockerfile_registry_mirror: no such file or directory
    integration_test.go:313: Failed to build image gcr.io/kaniko-test/docker-dockerfile_registry_mirror with kaniko command "[docker run --net=host -v /home/kbuilder/.config/gcloud:/root/.config/gcloud executor-image -f integration/dockerfiles/Dockerfile_registry_mirror -d gcr.io/kaniko-test/kaniko-dockerfile_registry_mirror --registry-mirror us-mirror.gcr.io -c git://github.com/GoogleContainerTools/kaniko]": exit status 1 Enumerating objects: 17206, done.
        Total 17206 (delta 0), reused 0 (delta 0), pack-reused 17206
        Error: error resolving dockerfile path: please provide a valid path to a Dockerfile within the build context with --dockerfile

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[darewreck54]

@greut Is it possible to support multiple registry-mirrors. If one fails, then it would use another one or the default. This is useful for use cases such as docker hub limitation with API calls. We could leverage off google mirror cache and if it doesn't have it go to docker hub to pull it into the cache.