Add base image (closes #4)

base/Dockerfile

@@ -0,0 +1,25 @@
+FROM openjdk:8-jre-alpine
+LABEL maintainer="Snowplow Analytics Ltd. <[email protected]>"
+
+# Snowplow components will be installed in this folder.
+ENV SNOWPLOW_PATH="/snowplow"
+ENV SNOWPLOW_CONFIG_PATH="${SNOWPLOW_PATH}/config" \
+    SNOWPLOW_BIN_PATH="${SNOWPLOW_PATH}/bin"
+
+# Create a snowplow group and user.
+RUN addgroup snowplow && \
+    adduser -S -G snowplow snowplow
+
+# Install the components common to all apps.
+# https://github.com/yelp/dumb-init: lightweight init system
+# su-exec: sudo replacement
+RUN apk add --no-cache dumb-init su-exec ca-certificates wget
+
+# /snowplow/bin is meant to contain the application jar.
+# /snowplow/config is meant to contain the necessary configuration.
+RUN mkdir -p ${SNOWPLOW_BIN_PATH} && \
+    mkdir -p ${SNOWPLOW_CONFIG_PATH} && \
+    chown -R snowplow:snowplow ${SNOWPLOW_PATH}
+
+# Expose the configuration directory.
+VOLUME ${SNOWPLOW_CONFIG_PATH}