back to Web_Application_Hosting

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.

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

Python

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

[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

Login linger mode

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

Pubapps Systemd Use

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