albertw/r-apache repository overview

⁠R-apache Docker image

Docker image based on rocker/tidyverse for deploying Shiny apps to Heroku. Runs an Apache2 reverse proxy in front of an R Shiny app so we can add some middleware, such as authentication/authorization.

⁠Usage

This image is meant to provide a base for packaging Shiny apps; by default it runs the 01_hello packaged with Shiny. Includes a helper script /runApp.r to make it easy to call shiny::runApp() from the shell.

A minimal Dockerfile would look something like:

FROM albertw/r-apache:latest
COPY /app.R /app/app.R
CMD ["/runApp.r", "/app"]

Apache site configuration is in /etc/apache2/sites-available/shiny.conf. Overwrite to customize, e.g., add authentication. The default listens on all domains and proxies to 127.0.0.1:3939, where the Shiny app runs.

To add additional packages, either use the install.r script (from littler) or run packrat::restore() as part of the build process, e.g.,

FROM albertw/r-apache:latest
RUN install.r wrapr rquery semantic.dashboard
RUN cd /app && r 'packrat::restore()'
COPY /app.R /app/app.R
CMD ["/runApp.r", "/app"]

⁠What's included

⁠Apache configuration

Heroku runs Docker containers in a slightly non-standard way:

• Container must bind to a port specified at run-time in the environment variable PORT
• Container must run as a normal non-root user that's not known ahead of time

Run-time port specification is simple: hard-coded listening port in /etc/apache2/ports.conf was replaced with the environment variable.

Non-root user is a little trickier because Apache needs the user to be specified in the config file. For now:

• Set user and group in /etc/apache2/envvars. This is just a shell script so get values from id -un and id -gn.
• Set a bunch of directories in /var to be globally readable and writable.

Finally, to get logging through Docker to work, the default log files are symlinked to stdout/stderr.

⁠Rprofile

shiny.port and shiny.host options are set in the site-wide R profile. (/usr/local/lib/R/etc/Rprofile.site)

options(shiny.host = "127.0.0.1", shiny.port = 3838)

⁠Scripts

• /entrypoint.sh: specified as the ENTRYPOINT of the image. Runs Apache and the R process (specified in the Dockerfile CMD) in the background and monitors them; exits if either process exits. In addition, it reparents itself under tini if it detects it's running as PID 1 (useful for local testing, Heroku does not seem to run Docker containers as PID 1 though).
• /runApp.r: simple wrapper around shiny::runApp() that takes an app directory as its argument. Can optionally specify listening port and host with -p and -h flags.