Docker with yarn

Definitely pay attention to docker caching. Basically you want to run the most stable instructions earlier than less stable ones. Instructions which would result in the same image changes as an earlier run should not be rerun (exluding issues with ENV/ARG instructions). But once an instruction does need to be run, all instructions following will be run regardless of what's in the cache.

.dockerignore will also help, but it can be easy for things to slip in. I've adopted the practice of inverting the file by ignoring everything and then specifying exactly what should be copied.

To minimise fetching from the web, I like using the yarn offline cache. This stores the tarballs of installed dependencies and reuses them for future installs. You get the benefit over npm rebuild of fresh installs every time (if the cache has been invalidated). You configure the offline cache with a .yarnrc file which could be in your home directory but for this purpose you keep one in your repo along with a directory to store the tarballs.

You have the option of checking-in the mirror directory to your repo. A typically large npm module install will still only be in the region of 20 megs.

If you use the files below, customised for your needs, and run yarn locally, the yarn-offline-mirror will contain the tarballs needed to install the app.

.dockerignore

*!yarn-offline-mirror/!src/!package.json!yarn.lock!.yarnrc

.yarnrc

# THIS IS AN AUTOGENERATED FILE. DO NOT EDIT THIS FILE DIRECTLY.# yarn lockfile v1yarn-offline-mirror "./yarn-offline-mirror"

Dockerfile

ENV HOME /usr/src/WORKDIR $HOME# copy the tarballsCOPY ["yarn-offline-mirror", "$HOME/yarn-offline-mirror/"]# copy files needed for the installCOPY ["package.json", "yarn.lock", ".yarnrc", "$HOME/"]# the offline flag will mean that an error is raised if any# module needs to be fetched remotely. It can be removed to allow# yarn to fetch any missing modules if that was to happen.RUN yarn --offline --frozen-lockfile --link-duplicates# copy the rest.. could be further broken up into multiple instructions# for cache optimisationCOPY . $HOMECMD npm start

You should use the docker cache better.

If you have your Dockerfile prepared as follows:

FROM node:carbonCOPY package.json yarn.lock /appRUN cd /app \    && yarn install --pure-lockfileCOPY . /appCMD doStuff

The docker build won't touch the package.json unless it has changed. The next RUN command won't execute unless the cache has been invalidated in the earlier step.

NOTE: keep the node_modules inside your .dockerignore file