Update the serving Elixir example to freeze to 1.6 and to be compatible with Google Cloud Build

serving/samples/helloworld-elixir/.gcloudignore

@@ -0,0 +1,24 @@
+# For building with Google Cloud Build using the gcloud command line tool.
+# Similar to .gitignore, except we want the /config/*.secrete.exs uploaded for the build.
+
+# App artifacts
+/_build
+/db
+/deps
+/*.ez
+
+# Generated on crash by the VM
+erl_crash.dump
+
+# Generated on crash by NPM
+npm-debug.log
+/assets/package-lock.json
+
+# Static artifacts
+/assets/node_modules
+
+# Since we are building assets from assets/,
+# we ignore priv/static. You may want to comment
+# this depending on your deployment strategy.
+/priv/static/
+

serving/samples/helloworld-elixir/Dockerfile

@@ -1,4 +1,5 @@
-FROM elixir:alpine
+FROM elixir:1.6.6-alpine
+
 ARG APP_NAME=hello
 ARG PHOENIX_SUBDIR=.
 ENV MIX_ENV=prod REPLACE_OS_VARS=true TERM=xterm
@@ -8,6 +9,7 @@ RUN apk update \
     && mix local.rebar --force \
     && mix local.hex --force
 COPY . .
+
 RUN mix do deps.get, deps.compile, compile
 RUN cd ${PHOENIX_SUBDIR}/assets \
     && npm install \
@@ -17,8 +19,18 @@ RUN cd ${PHOENIX_SUBDIR}/assets \
 RUN mix release --env=prod --verbose \
     && mv _build/prod/rel/${APP_NAME} /opt/release \
     && mv /opt/release/bin/${APP_NAME} /opt/release/bin/start_server
+
 FROM alpine:latest
 RUN apk update && apk --no-cache --update add bash openssl-dev
+
+RUN addgroup -g 1000 appuser && \
+    adduser -S -u 1000 -G appuser appuser
+
+RUN mkdir -p /opt/app/var
+RUN chown appuser /opt/app/var
+
+USER appuser
+
 ENV PORT=8080 MIX_ENV=prod REPLACE_OS_VARS=true
 WORKDIR /opt/app
 EXPOSE 8080

serving/samples/helloworld-elixir/README.md

@@ -38,15 +38,16 @@ Now you can visit [`localhost:4000`](http://localhost:4000) from your browser.
 
    ```docker
    # Start from a base image for elixir
-   FROM elixir:alpine
+   # Phoenix works best on pre 1.7 at the moment.
+   FROM elixir:1.6.6-alpine
 
    # Set up Elixir and Phoenix
    ARG APP_NAME=hello
    ARG PHOENIX_SUBDIR=.
    ENV MIX_ENV=prod REPLACE_OS_VARS=true TERM=xterm
    WORKDIR /opt/app
 
-   # Compile assets.
+   # Update nodejs, rebar, and hex.
    RUN apk update \
        && apk --no-cache --update add nodejs nodejs-npm \
        && mix local.rebar --force \
@@ -69,10 +70,19 @@ Now you can visit [`localhost:4000`](http://localhost:4000) from your browser.
    # Prepare final layer
    FROM alpine:latest
    RUN apk update && apk --no-cache --update add bash openssl-dev
-   ENV PORT=8080 MIX_ENV=prod REPLACE_OS_VARS=true
-   WORKDIR /opt/app
+
+   # Add a user so the server will run as a non-root user.
+   RUN addgroup -g 1000 appuser && \
+       adduser -S -u 1000 -G appuser appuser
+   # Pre-create necessary temp directory for erlang and set permissions.
+   RUN mkdir -p /opt/app/var
+   RUN chown appuser /opt/app/var
+   # Run everything else as 'appuser'
+   USER appuser
 
    # Document that the service listens on port 8080.
+   ENV PORT=8080 MIX_ENV=prod REPLACE_OS_VARS=true
+   WORKDIR /opt/app
    EXPOSE 8080
    COPY --from=0 /opt/release .
    ENV RUNNER_LOG_DIR /var/log