Caching a single file on Travis CI

问题

Inside my build on travis I need to first download a large .tar.gz file.

This .tar.gz never changes so it's a good idea cache it.

The .tar.gz it's downloaded inside my Dockerfile:

RUN curl ftp://mycompanyftp.com/foo/bar/mylargefile.tar.gz -o /tmp/mylarge.tar.gz

With that the docker container build with the file inside.

How can I cache this file?

PS: It's also possible to download the file on before_install and use docker ADD to put it inside the Docker container.

回答1:

This is not possible as long as you have this command in your dockerfile.

Instead, I suggest that you put this command in your .travis.yml file and download the file as part of the pre-build activities:

before_install: |
  if ! [ -f ./src/mylarge.tar.gz ]; then
    curl ftp://mycompanyftp.com/foo/bar/mylargefile.tar.gz -o ./src/mylarge.tar.gz;
  fi

install: |
  ./scripts/build.sh;

script: |
  ./scripts/test-integration.sh;

cache:
  directories:
    - $TRAVIS_BUILD_DIR/src/

after_success: |
  ./scripts/deploy.sh;

As you can see, the before_install section will download the file if it does not exist already. The cache section will tell Travis to keep the ./src/ directory and restore it at the beginning of your next build so it will not be downloaded for a second time.

In your dockerfile, what you want to do now instead of downloading is to just copy the local file into the container:

COPY ./src/mylargefile.tar.gz /tmp/mylargefile.tar.gz

You can read more about caching on Travis CI on their docs page.

来源：https://stackoverflow.com/questions/35203169/caching-a-single-file-on-travis-ci