Shiny app docker container not loading in browser

Question

I containerised a shiny app and attempted to deploy it on GCP using Kubernetes but each time I obtain the external IP address and load it in the browser, I get the "this site cannot be reached connection refused" error. So I have attempted to run the container on my localhost to troubleshoot and now I get the "127.0.0.1 didn’t send any data. ERR_EMPTY_RESPONSE" error. I searched tirelessly online for a solution but nothing seems to work for me. Plus none of the solutions on are for a shiny app docker container. Many of the fixes mention the port but I am still stuck. I have xampp installed on my mac by the way. Is it possible that xampp and my docker container are attempting to share the same port or is there a problem with my Docker file code? Pardon me but I am new to containers and have only been following the documentation procedure up till now. Below is my Docker file code:

Dockerfile

# Install R version 3.5.1
FROM r-base:3.5.1

# Install Ubuntu packages
RUN apt-get update && apt-get install -y \
sudo \
gdebi-core \
pandoc \
pandoc-citeproc \
libcurl4-gnutls-dev \
libcairo2-dev/unstable \
libxt-dev \
libssl-dev

# Download and install ShinyServer (latest version)
RUN wget --no-verbose https://s3.amazonaws.com/rstudio-shiny-server-os- 
build/ubuntu-12.04/x86_64/VERSION -O "version.txt" && \
VERSION=$(cat version.txt)  && \
wget --no-verbose "https://s3.amazonaws.com/rstudio-shiny-server-os- 
build/ubuntu-12.04/x86_64/shiny-server-$VERSION-amd64.deb" -O ss-latest.deb && 
\
gdebi -n ss-latest.deb && \
rm -f version.txt ss-latest.deb

# Install R packages that are required
# TODO: add further package if you need!
RUN R -e 

"install.packages(c('shiny','shinyjs','tools','foreign','XLConnect'), 
repos='http://cran.rstudio.com/')"

# Copy configuration files into the Docker image
COPY shiny-server.conf  /etc/shiny-server/shiny-server.conf
COPY /app /srv/shiny-server/

# Make the ShinyApp available at port 80
EXPOSE 80

# Copy further configuration files into the Docker image
COPY shiny-server.sh /usr/bin/shiny-server.sh

CMD ["/usr/bin/shiny-server.sh"]

I would appreciate it if someone could assist me.

Answer 1

You don't need shiny-server.

add

app <- shinyApp(ui = ui, server = server)
runApp(app, host ="0.0.0.0", port = 80, launch.browser = FALSE)

to your R script and

EXPOSE 80
CMD ["R", "-e", "library(shiny); source('/root/pathToYourScript/script.R')"]

to your Dockerfile.

Answer 2

I had to first create a Rprofile.site file and place it in the same directory as the dockerfile and shinyapp. Then I created my own base image with all the necessary libraries for the app and called it from my dockerfile. Here is the final code:

Rprofile.site

local({
options(shiny.port = 3838, shiny.host = "0.0.0.0")
})

Dockerfile

FROM bimage_rpackages

# Copy the app to the image
RUN mkdir /root/shinyapp
COPY app/shinyapp /root/shinyapp

COPY app/Rprofile.site /usr/lib/R/etc/

# Make the ShinyApp available at port 3838
EXPOSE 3838

CMD ["R", "-e", "shiny::runApp('/root/shinyapp')"]