add new post about automated deployment

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Adam Piontek 2021-04-08 17:54:07 -04:00
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%{
title: "Elixir Phoenix Automated Deployment with Gitea/systemd",
id: "elixir-phoenix-automated-deployment-gitea-systemd-git",
date: ~N[2021-04-08 17:49:00],
author: "Adam Piontek",
tags: ~w(tech elixir phoenix notes coding automated deployment gitea git systemd)
}
---
I don't know if this is the *"right"* way to do this, but it's working for me at the moment, and since it took a bit to figure out, I figured I'd write up my notes.
My needs are simple: when I'm happy with an update to my blog, or another elixir phoenix app I run, Shift73k (or more in the future), I'd like to be able to just commit to my repository, and then have those changes go live. At the moment I run both gitea and my other little apps on the same Linode, so I was able to set it up like this:
<!--more-->
### deployment script
First, the Phoenix deployment makes use of [Releases](https://hexdocs.pm/phoenix/releases.html), though I'm not doing anything fancy to track versions or anything like that.
This means the general upload procedure looks like this, and I can put it in a bash script to make updating a bit easier:
```bash
#!/usr/bin/env bash
cd /opt/myapp73k
# update from master
/usr/bin/git pull 73k master
# fetch prod deps & compile
/usr/bin/mix deps.get --only prod
MIX_ENV=prod /usr/bin/mix compile
# perform any migrations
MIX_ENV=prod /usr/bin/mix ecto.migrate
# update node packages via package-lock.json
/usr/bin/npm --prefix /opt/myapp73k/assets/ ci
# rebuild static assets:
rm -rf /opt/myapp73k/priv/static/*
/usr/bin/npm --prefix /opt/myapp73k/assets/ run deploy
MIX_ENV=prod /usr/bin/mix phx.digest
# rebuild release
MIX_ENV=prod /usr/bin/mix release --overwrite
# restart service
sudo /bin/systemctl restart myapp73k.service
```
### sudo permissions
To allow the user that's running the script to invoke `sudo` we need to give it explicit permission, e.g. by placing the following in a file like `/etc/sudoers.d/deploy_hooks`:
```bash
git ALL=(runuser) NOPASSWD: /home/runuser/deploy_hooks/deploy-myapp73k.sh
runuser ALL= NOPASSWD: /bin/systemctl restart myapp73k.service
```
The first line allows the user `git` to run the script `/home/runuser/deploy_hooks/deploy-myapp73k.sh` *as the user* with username `runuser` -- and without requiring a password. Permissions should only allow the `runuser` accoutn to modify the script, so someone with access to the `git` account can't modify it to make it run something else.
The second line allows the user `runuser` to run *only* the command `/bin/systemctl restart myapp73k.service` without a password. Doing anything else with sudo will still ask for a password.
What this enables is that a git post-receive hook, running as user `git`, can call the deploy script, which runs as user `runuser` and performs the app update, which can finish by calling `systemctl restart`{:.lang-bash}
### gitea post-receive hook content
For git to run the deployment script after the repository receives a new commit, we set a git hook. But I want to be able to commit development branches to the repository without those commits getting deployed, so I want the hook to do nothing unless it's a commit to the master branch (could be any other branch, say "prod")
My hook looks something like this:
```bash
#!/usr/bin/env bash
while read oldrev newrev refname
do
branch=$(git rev-parse --symbolic --abbrev-ref $refname)
if [ "master" = "$branch" ]; then
sudo -u runuser /home/runuser/deploy_hooks/deploy-myapp73k.sh
fi
done
```
Here we can see the hook checks the branch first, and if master, runs `sudo -u runuser`{:.lang-bash} to run the script as user `runuser`
### elixir phoenix release systemd unit
That should just about do it, but as an extra note, here's the elixir phoenix release systemd unit:
```systemd
[Unit]
Description=MyApp73k service
After=local-fs.target network.target
[Service]
Type=simple
User=runuser
Group=runuser
WorkingDirectory=/opt/myapp/_build/prod/rel/myapp73k
ExecStart=/opt/myapp73k/_build/prod/rel/myapp73k/bin/myapp73k start
ExecStop=/opt/myapp73k/_build/prod/rel/myapp73k/bin/myapp73k stop
#EnvironmentFile=/etc/default/myApp.env
Environment=LANG=en_US.utf8
Environment=MIX_ENV=prod
Environment=PORT=4000
LimitNOFILE=65535
UMask=0027
SyslogIdentifier=myapp73k
Restart=always
[Install]
WantedBy=multi-user.target
```
I hope this is helpful to someone --- most of all my future self!