pyNetConnMon

Monitor Internet (or network) connectivity. Send mail on network interruptions.

Description

pyNetConnMon is an Internet connectivity monitor. It tries to periodically connect to a given service and reports failures via mail.

Checkout and configuration of pySendMail submodule

pyNetConnMon uses git submodules, specifically it uses pySendMail to send mail reports about connectivity losses. After checkout, submodules have to be populated by the following commands:

git submodule init
git submodule update

Afterwards it is necessary to configure pySendMail in order to be able to send mails. Refer to the documentation of pySendMail and create a config file in the pySendMail subdirectory.

Options

All of the following time-based arguments are specified in seconds.

• -h, --help: show this help message and exit
• -a ADDRESS, --address ADDRESS: host address to check (default: 8.8.8.8)
• -p PORT, --port PORT: host port to check (default: 53)
• -i INTERVAL, --interval INTERVAL: check interval (default: 2.0)
• -t TIMEOUT, --timeout TIMEOUT: connection timeout (default: 2.0)
• -m MIN_INTERRUPTION, --min-interruption MIN_INTERRUPTION: ignore interruptions smaller than this (default: 5.0)
• -bmin BACKOFF_MIN, --backoff-min BACKOFF_MIN: minimum time to pass between mail reports (for backoff, default: 60.0)
• -bmax BACKOFF_MAX, --backoff-max BACKOFF_MAX: maximum time to pass between mail reports (for backoff, default: 3600.0)
• -bstep BACKOFF_STEP, --backoff-step BACKOFF_STEP: backoff wait time increment for subsequent connection losses (default: 300.0)

Example

Monitor Internet connectivity by using Google's DNS server 8.8.8.8:53 from the default settings:

./pyNetConnMon.py

Backoff mechanism

Repeated, continuous failures will result in a flood of mail reports. Therefore pyNetConnMon comes with a simple backoff mechanism. After each mail, the wait time until the next mail will be send is increased by BACKOFF_STEP, starting with BACKOFF_MIN for the first increment. As soon as this wait time has passed, a mail report will get sent, including all network interruptions from that time span. Continuous network failures increase this backoff, with an upper bound of BACKOFF_MAX. BACKOFF_MAX is also used as time after which to reset the backoff to zero if interruptions stay absent.

Autostart

To start the script automatically after boot you can use a crontab entry or init script. Here is an example for starting the script automatically at boot inside a tmux session, via cron (crontab -e as a regular user, i.e. non-root):

@reboot              cd ~/pyNetConnMon && SHELL=/bin/bash tmux new -d -s pynetconnmon "python3 pyNetConnMon.py"

You can attach to it via tmux a -t pynetconnmon and detach from it via the default key binding ctrl-b d.

License

GPL v3 (c) Alexander Heinlein