Docker build improvements. (#150)

* Add .dockerignore to stop copying .git/, npm_modules/, and dist/ into image.

Remove unneeded and slow recursive chown from Dockerfile.

* Switch from npm to yarn to install packages.

* Dockerfile installs node-v6.11.3 and yarn-1.0.2 as packages.

.dockerignore

@@ -0,0 +1,5 @@
+.dockerignore
+.git*
+dist/
+dist/*
+node_modules*

docker/thresher_api/Dockerfile

@@ -9,10 +9,46 @@ COPY /docker/bashrc_to_docker /root/.bashrc
 ARG DEBIAN_FRONTEND=noninteractive
 
 RUN apt-get update -q && apt-get install -q -y \
+        curl apt-transport-https apt-utils \
         gcc \
         gettext \
         postgresql-client libpq-dev \
-        vim git curl less psmisc
+        vim less psmisc \
+        python
+
+WORKDIR /home/download
+ARG NODEREPO="node_6.x"
+ARG DISTRO="jessie"
+# Only newest package kept in nodesource repo. Cannot pin to version using apt!
+# See https://github.com/nodesource/distributions/issues/33
+#RUN curl -sSO https://deb.nodesource.com/gpgkey/nodesource.gpg.key
+#RUN apt-key add nodesource.gpg.key
+#RUN echo "deb https://deb.nodesource.com/${NODEREPO} ${DISTRO} main" > /etc/apt/sources.list.d/nodesource.list
+#RUN echo "deb-src https://deb.nodesource.com/${NODEREPO} ${DISTRO} main" >> /etc/apt/sources.list.d/nodesource.list
+#RUN apt-get update -q && apt-get install -q -y 'nodejs=6.11.3*'
+
+# So we have to download specific package in order to pin version of node.
+# dpkg doesn't install package dependencies automatically, we have to do it.
+# This nodejs package has a dependency on the 'python' package, installed above.
+# Since this is a python:2.7-slim image, you would think python packages
+# are installed. But the Dockerfile installs Python from source, not packages.
+
+# jessie specific version not provided starting with 6.11.3
+#ARG NODE_PACKAGE=nodejs_6.11.2-1nodesource1~jessie1_amd64.deb
+ARG NODE_PACKAGE=nodejs_6.11.3-1nodesource1_amd64.deb
+RUN curl -sSO "https://deb.nodesource.com/node_6.x/pool/main/n/nodejs/${NODE_PACKAGE}"
+RUN dpkg -i ${NODE_PACKAGE}
+
+# npm upgrade doesn't work due to bug in nodejs .deb package!
+# Must install nodejs at terminal for npm upgrade to work!
+#RUN npm install -g npm
+#RUN npm --version
+
+RUN curl -sSO https://dl.yarnpkg.com/debian/pubkey.gpg
+RUN apt-key add pubkey.gpg
+RUN echo "deb https://dl.yarnpkg.com/debian/ stable main" | tee /etc/apt/sources.list.d/yarn.list
+
+RUN apt-get update -q && apt-get install -q -y 'yarn=1.0.2*'
 
 RUN rm -rf /var/lib/apt/lists/*
 
@@ -30,15 +66,6 @@ ARG HOME=/home/thresher
 RUN groupadd -g ${GROUP_ID} ${USER} && \
       useradd --shell /bin/bash --home ${HOME} -u ${USER_ID} -g ${GROUP_ID} ${USER}
 
-WORKDIR /home/download
-# https://nodejs.org/dist/v6.10.3/node-v6.10.3-linux-x64.tar.xz
-ARG NODE_VERSION=v6.10.3
-ARG NODE_FILE=node-${NODE_VERSION}-linux-x64.tar.xz
-# This merges files into /usr/local/{bin,include,lib,share}
-# So node is installed for all users
-RUN curl -O https://nodejs.org/dist/${NODE_VERSION}/${NODE_FILE}
-RUN tar -C /usr/local --strip-components 1 -xf ${NODE_FILE}
-
 # Let Django copy to static dir as regular user
 WORKDIR /var/www
 RUN chown ${USER}:${USER} /var/www
@@ -47,20 +74,18 @@ ENV PYTHONPATH /home/thresher
 # note: Development config mounts the git repo root on this path.
 # Copy minimal files needed to npm install to try
 # and re-use cache
+ENV WEBPACK_BUILD_DIR /home/thresher
 WORKDIR /home/thresher
+RUN chown ${USER}:${USER} /home/thresher
 COPY /package.json /home/thresher
-RUN chown -R ${USER}:${USER} /home/thresher
+COPY /yarn.lock /home/thresher
 
-ENV WEBPACK_BUILD_DIR /home/thresher
-WORKDIR /home/thresher
 USER ${USER}
-RUN npm install
+RUN yarn install
 
 # Now copy the rest of the repo into the image - any file change breaks build cache
+# .dockerignore must exclude node_modules/ and dist/
 COPY / /home/thresher
-USER root
-RUN chown -R ${USER}:${USER} /home/thresher
-USER ${USER}
 RUN npm run deploy:quiet
 
 COPY /docker/bashrc_to_docker ${HOME}/.bashrc