servicehandler 0.9

Systemd service handler

Systemd service handler (servicehandler)

servicehandler is a Python library that provides an orchestrator for systemd services. It abstracts services as objects and implements helper methods, wrapping the systemctl command

Using this package does not require root permissions, as the service manager used is the one of the current user (the service configuration files are in /usr/lib/systemd/user/)

Description

The first thing to handle services is to create a service unit file (in /usr/lib/systemd/user/my-service.service) like the following:

[Unit]
Description=My service

[Service]
ExecStart=/usr/bin/python3 /home/user/service_script/main.py
Environment=PATH=/bin:/usr/bin:/usr/local/bin
WorkingDirectory=/home/user/service_script/

[Install]
WantedBy=multi-user.target

Depending on how you created the service file you may need to provide access to the user through sudo chmod 644 my-service.service

Usage

Control the state of a service

import servicehandler as sh

# Create a new service handler
my_service = sh.ServiceHandler('MyService','my-service.service')

# Check current state
my_service.state()
<ServiceState.STOPPED: 2>

# Start the service
> my_service.start()
MyService changed state to ServiceState.RUNNING
<Response.OK: 1>

# Try to start again the service
> my_service.start()
<Response.ALREADY: 2>

# Terminate the service
> my_service.stop()
MyService changed state to ServiceState.STOPPED
<Response.OK: 1>

# Kill the service
# In this specific case, the unit file was configured with restart=on-failure (automatic restart)
> my_service.kill()
<Response.OK: 1>

Control the enablement_state of a service (whether it starts automatically on system startup)

# Check current enablement_state
> my_service.enablement_state()
<ServiceEnablementState.DISABLED: 2>

# Enable the service
> my_service.enable()
Created symlink /home/user/.config/systemd/user/multi-user.target.wants/my_service.service → /usr/lib/systemd/user/my_service.service.
MyService changed enablement state to ServiceEnablementState.ENABLED
<Response.OK: 1>

# Disable the service
> my_service.disable()
Removed /home/user/.config/systemd/user/multi-user.target.wants/my_service.service.
MyService changed enablement state to ServiceEnablementState.DISABLED
<Response.OK: 1>

Iterate over different services and perform batch operations

import servicehandler as sh

service_A = sh.ServiceHandler('ServiceA','A-config-file.service')
service_B = sh.ServiceHandler('ServiceB','B-config-file.service')
service_C = sh.ServiceHandler('ServiceC','C-config-file.service')

services = [ServiceA, ServiceB, ServiceC]

# Iterate over the services easily
for sr in services:
    if sr.state == sh.ServiceStatus.STOPPED:
        sr.restart()
    print(sr)

Installation

Install using pip

This package is available on PyPI and it can be installed using pip:

pip install servicehandler

Build from source

To build and install the package from source:

git clone https://github.com/albertosantagostino/systemd-servicehandler
cd systemd-servicehandler
python3 setup.py install

Development history and use cases

Manage multiple services from a single entry-point

This library was developed while working on a Telegram bot overlord manager, used to handle other bots (and services) running on the same platform, providing a single point of access to the user

In this scenario multiple bots run on a headless Raspberry Pi Zero. In order to start them when needed, check their logs and interact with them without opening an SSH session every time, a brand new all-powerful Telegram bot was created, weaponized with this new package

License

The package is distributed under the MIT License