Systemd for the Swift app

This post is for server-side Swift developers.

All apps on a server need to be launched under some watchdog daemon. You might already be using supervisord or systemd.

This article will show you how to simplify your life with systemd by integrating it directly into your app.

First, let's look at how we usually work with systemd and the steps needed to set up a service.

Pure systemd

Setting Up

Create a unit configuration file manually by searching for examples online and saving it in the /etc/systemd/system folder.

Not so easy, right? Most people give up somewhere around here.

Management

You have to remember a few simple commands:

systemctl start   myapp.service
          restart myapp.service
          stop    myapp.service

But also the name you gave your service 🙉

Don't forget to start your app after creating the unit configuration file.

If You Want to Remove the Service

systemctl stop myapp.service
systemctl start clean --all

Not too hard to remember, but still...

Logs

This is where most people get lost, because logs can either be stored in some .log files somewhere in the system, or you have to use journalctl commands like these:

For live logs:

journalctl -u myapp -f

For the last few log lines:

journalctl -u myapp -n 100 --no-pager

I believe it's a bit hard to remember, and I often use the up-arrow in the console to find the right command from history.

🍰 The Swift Plugin Way

SwiftSystemd to the rescue!

It provides a simple way to handle all the above without headaches.

⚡️ Installation

Open your app's Package.swift and add just one line:

.package(url: "https://github.com/MihaelIsaev/SwiftSystemd.git", from:"1.0.0")

After that, you're ready to go!

🛠️ Setting Up

Let's see how to create a proper unit configuration file for systemd. In the folder with your app, just run:

swift run systemd install

It will prompt you with a few questions in the console, and then you're done.

Or you can specify the answers in advance like this:

swift run systemd install -c release -t App -u mike

where
-c or --config is for configuration: release or debug
-t or --target is for Executable target name
-u or --user is for user under which the service will run

This command generates the following unit config file:

[Unit]
Description="AppName"
After=network.target

[Service]
User={user}
EnvironmentFile=/path/to/AppName/.env
WorkingDirectory=/path/to/AppName
TimeoutStopSec=2

Restart=always

ExecStart=/path/to/AppName/.build/{config}/{target}

[Install]
WantedBy=multi-user.target

That's it! You've set up your app the right way in just two simple steps, and it's already running.

📋 Logs

One of the most essential tasks is watching logs, and it's as easy as:

swift run systemd logs

This displays live logs of your app via journalctl.

swift run systemd logs --limit 100

This shows the last 100 lines from your app's log via journalctl

Easy to remember!

🎛️ Management

You can check the app's status by running:

swift run systemd status

Or manage the app state with the following commands:

swift run systemd start    # starts the app
                  stop     # stops the app
                  restart  # restart the app
                  disable  # temporarily disables the app
                  enable   # re-enables the app

You can also send a kill signal to the app:

swift run systemd kill

🧹 Cleaning Up

If you no longer need the service, you can remove it easily:

swift run systemd uninstall

This deletes the systemd configuration file and stops the service if it's still active.

👏 Conclusion

I believe you can now throw away all your systemctl and journalctl notes, just like I did!

❤️ Feel free to contribute!