Backend

The backend can be deployed on any Linux server. (It is, in theory, possible to deploy it on Windows and macOS as well, as Elixir runs on those platforms, but we do not test that the backend works those platforms.)

Deployment methods

Scripted install on Linux server

  1. On the server, configure the backend.

  2. If you are running on Ubuntu 20.04, you can run the automated installation script:

    curl -LO https://raw.githubusercontent.com/source-academy/backend/stable/deployment/init.sh
# inspect init.sh
sudo bash init.sh

    The script downloads and extracts the precompiled Linux release, sets up a systemd unit file, and starts the backend. The configuration file should be at /etc/cadet.exs.

    If you are not running Ubuntu 20.04, you may try the script, but the precompiled script may not work if your glibc version is not new enough. In that case, manually compile the backend and install it.

  3. Check that the backend is accessible at http://localhost:4000 (on the server).

  4. Note that you need a service to act as a TLS termination proxy for the backend. If you are following our Terraform deployment, this will be AWS’s Elastic Load Balancer.

    If not, consider using Nginx. This guide may be helpful, but instead of having an upstream with multiple endpoints, just proxy_pass http://localhost:4000.

    Alternatively, you can terminate SSL directly at the backend; follow this guide (the configuration changes can be merged into the endpoint key in cadet.exs).

  5. Check that the backend is accessible over HTTPS from your own computer.

  6. Next, follow the guide to manually setup the optional AWS services, if needed.

To update the backend, repeat steps 2, 3, 4, and 6.

Manual compile

  1. Compile the backend.

  2. Transfer the package to the server the backend will be run on.

  3. On the server, configure the backend.

  4. Install this systemd unit file onto the server, at /etc/systemd/system/cadet.service.

    [Unit]
After=network.target
Requires=network.target
StartLimitIntervalSec=0

[Service]
Type=simple
TimeoutStartSec=0
Restart=always
RestartSec=5
ExecStart=/opt/cadet/bin/cadet start
User=nobody
Environment=HOME=/opt/cadet/tmp
Environment=PORT=4000

[Install]
WantedBy=multi-user.target

  5. Place this Bash script into the same directory as the package.

    #!/bin/bash

BASEDIR=/opt/cadet

sudo systemctl stop cadet
sudo rm -rf "$BASEDIR"
sudo mkdir -p "$BASEDIR"
sudo tar -zxf cadet-0.0.1.tar.gz -C "$BASEDIR" --no-same-owner
sudo mkdir -p "$BASEDIR/tmp"
sudo chmod 1777 "$BASEDIR"/{tmp,lib/tzdata-*/priv/tmp_downloads}
sudo chmod a+x "$BASEDIR"/{bin/cadet,erts-*/bin/*,releases/*/{iex,elixir}}
sudo chown -R nobody:nogroup "$BASEDIR"/lib/tzdata-*/priv/{release_ets,latest_remote_poll.txt}
sudo systemctl start cadet
# this just loops until we can reach the running application
while ! "$BASEDIR/bin/cadet" rpc 1; do
   sleep 0.5
done
sleep 5 # Allow application to fully start up - avoid a race condition
"$BASEDIR/bin/cadet" rpc Cadet.Release.migrate

    (Note: adapt as needed. This script makes it so the extracted files are owned by root, but gives write access to certain files which are modified at runtime. It assumes that the backend is going to be run as nobody.)

    Make it executable and execute the script.

    The script extracts the release package to /opt/cadet. If you wish to install it somewhere else, change the script and systemd service file accordingly.

  6. Continue with the rest of the steps in the scripted install guide.