April 14, 2018
By: Harlan Iverson

ClojureScript on RasPi

Recently we switched from Tinkerboard back to RasPi3B, the original TinyDC box we built in Jan/Dec... it's been hosting the website since then, and doing good. We returned because the 24x7 live stream came online, and it seemed like a fun idea to do work on stream, yet we use use the TBoard for other projects that overlap in usage time, sometimes. Ie. use TinyDC as the desktop to share at all times, and enhance dev functionality as needed. While I can bring the TBoard over each day before I begin the stream, that's been cumbersome. Instead, we can use it to do heavy lifting for things that are only required while in the thick of development, or similar activities... and start the stream on our always-on desktop.

So the TBoard is back online as a build box, to split the load between development/UI on our workstation, and compliling/hosting with more resources. There's been no reinstall, we're using the prior image... but I've setup sshfs with good options and Figwheel with working options to make remote development possible–it's the same theory as setting up development in Vagrant, Docker, or AWS. Debuggers can be set up to talk to remote hosts, as they mostly operate over sockets.

Here are the useful configs to develop a ClojureScript project remotely.

1. Setup

On the server node, SSHFS mount the directory on dev... usually from within screen:


# connect to server, create our mount point
mkdir -p $HOME/mnt/uspooge-app

Next we can setup our ClojureScript project with the right options to build on a non-localhost. Inside of project.clj, change these options:

(defproject ;...
  :cljsbuild {:builds
              [{:id "dev"
                :figwheel {
                  :websocket-host :js-client-host ; connect to the client's provided host
               {:id "min"
                :compiler {
                  :optimizations :whitespace ; :advanced is better for prod, but too much for Rpi..

  :figwheel {:hawk-options {
               :watcher :polling ; slow but lets us work in docker/ssfhs

2. Daily use

Open or reconnect screen, session named dev:

screen -RAd dev

From within screen, mount the filesystem:

sshfs \
  pirate@$DEV_IP:p/uspooge-app \
  $HOME/mnt/uspooge-app \
  -o sshfs_sync \
  -o cache_timeout=0 \
  -o idmap=user

When it comes to the server side Clojure, we'll probably want to setup nrepl ports and debug ports. In general, to forward ports via an SSH connection you can add the -L option... eg:

  • ssh -L7888:localhost:7888 hi@tinkerboard

It's also helpful to have our local SSH agent manage our keys for us throughout our chain of connections via the -A option. We'll go into more depth on this as we explore YubiKey and PKI in the near future. I'll also likely write up Java debugging and Flight Recorder, now that it's being shipped with OpenJDK.


Another approach would be to leave all development environments on the build box and use sshfs to mount them into our local development environment. That's certainly not a bad option, but between the two the idea of keeping everything buildable on the main workstation and offloading work to the new machine seemed like a good approach to begin with. It's in line with Vagrant and Docker with builder containers, meaning tools have supported configuration options to support it, so it's a good approach.

Tags: blog