Introduction¶

If your web applications hosted on the pubapps infrastructure is architected to run as a backend process that is then reverse proxied via the pubweb webservers you will need a way to start the application when a server in the pubapps infrastructure (pubcontainer node, individual VM, or pubweb* webservers for lightweight backends) is restarted. We encourage you to consider using a systemd in user mode, which can automate the start/stop/restart process. This help article should help you create and use such a user systemd script for a web application.

Configuration¶

Systemd has two modes of operation - system-wide, which requires the service scripts to be in a system location and operated by root and a user mode. You will be using the user mode in pubapps.

Create a user systemd directory under your /pubapps/PROJECT/ $HOME directory in pubapps mkdir -p .config/systemd/user/
Add a service script for the application, e.g. ~/.config/systemd/user/projprod.service or projdev.service

Script examples for two commonly deployed types of apps are shown below:

Python Web Application¶

Example generic python web application systemd script

[Unit]
Description=MyProject (Production)
After=network.target

[Service]
Type=simple

WorkingDirectory=/pubapps/myinstance/myproject/prod/
ExecStart=/pubapps/myinstance/myproject/prod/conda/bin/python3 run/runserver.py
TimeoutSec=30
RestartSec=15s
Restart=always

[Install]
WantedBy=multi-user.target

R Shiny Web Application¶

[Unit]
Description=MyShinyApp
After=network.target
StartLimitIntervalSec=0

[Service]
Type=simple
Restart=always
RestartSec=5
WorkingDirectory=/pubapps/myproject/shinyapp/prod/app
ExecStart=nohup R --no-echo --no-restore --file=run.R > /pubapps/myproject/shinyapp/prod/logs/app.log 2>&1
EnvironmentFile=/pubapps/myproject/shinyapp/prod/env.sh

[Install]
WantedBy=multi-user.target

Use¶

Enable user linger mode to avoid having your application be shut down when you log out:
```
loginctl enable-linger $USER
```

Manage the application¶

Initial load of the configuration to enable the service
```
systemctl --user enable projprod
```
Reload configuration (after every change of the systemd service script)
```
systemctl --user daemon-reload
```
Start service
```
systemctl --user start projprod
```
Stop service
```
systemctl --user stop projprod
```
Restart service
```
systemctl --user restart projprod
```
Check if the service is running
```
systemctl --user status projprod
```

HA Setup on pubweb servers¶

We recommend that systemd served apps are started on the pubcontainer server that was listed in the support ticket.

We have two pubapps web/proxy servers providing a HA (High Availability) setup for serving your web application(s). If the main webserver goes down a secondary pubweb webserver will automatically take over.

If your application is running directly on the webserver then you will need to have a copy of the app running on both pubweb[1,2] servers to account for the HA (High Availability) configuration.

Additional Information¶

For additional information search web for 'systemd user mode'. E.g. https://wiki.archlinux.org/title/Systemd/User.