Deploying Native Reason/OCaml with Zeit's now.sh
I'm working on a new ReasonReact project that will need a stateful server, and I thought it might be nice to write that in Reason too :) but what's the best way to deploy it? And by "best" I mean "easiest, with a free-to-try option". After looking around a little, I settled on Zeit's now.sh.
What did I end up with? A 10mb docker image with a server inside!
Making the Docker image
## This is a two-stage docker file # This first stage has opam & a ton of other things # inside it. The full image is 1.4Gigs! Which is way # too big to keep around. FROM ocaml/opam:alpine as base RUN sudo apk update RUN sudo apk add m4 RUN sh -c "cd ~/opam-repository && git pull -q" RUN opam update # We'll need these two whatever we're building RUN opam install dune reason > /dev/null 2>&1 # need these two for building tls, which is needed by cohttp RUN opam depext conf-gmp.1 RUN opam depext conf-perl.1 RUN opam install tls > /dev/null 2>&1 # these are the dependencies for our server RUN opam install lwt cohttp cohttp-lwt-unix > /dev/null 2>&1 # Now we copy in the source code which is in the current # directory, and build it with dune COPY --chown=opam:nogroup . /hello-reason WORKDIR /hello-reason RUN sh -c 'eval `opam config env` dune build bin/Server.exe' ## Here's the second, *much* leaner, stage # It only contains the server binary! The reason we can do this # is we statically linked the binary (with -ccopt -static) FROM scratch COPY --from=base /hello-reason/_build/default/bin/Server.exe /server CMD ["/server"]
docker build -t hello . will take a minute, but at the end we get our 10mb image!
REPOSITORY TAG IMAGE ID CREATED SIZE hello latest 15ebe8ca2a7d 8 hours ago 9.85MB
Now run the docker image locally to make sure it's working
docker run -d -p 4321:8000 hello
If you open up
http://localhost:4321, You should see something like this:
Hello folks! This site has been visited 1 times Uri: //0.0.0.0:32780/ Method: GET Headers Headers: accept: text/html accept-encoding: gzip, deflate connection: keep-alive host: 0.0.0.0:32780 upgrade-insecure-requests: 1 Body:
Deploying with Now
This part is so easy it's almost not even worth mentioning. Once you've installed
now, you go to the directory with the
Dockerfile and run
now and it all just works! The first time you run it, the deploy will take a while because it's building the docker image for the first time. Subsequent builds will use the image cache, however, and will be much faster.
That's all, folks!
With OCaml native deployment this easy, there's no excuse not to do it! Now all we need are some super-easy-to-use server libraries... 🤔 cohttp and httpaf are quite powerful, but are a far cry from express.js or rust's rocket.