shunction

⛽ Self-hosted Azure Functions ftw! (Parody)

Shunction (SHell Function) is a parody of Azure Functions. When I first heard of Azure Functions, I knew I had to write this.

In short, shunction given a folder of function scripts, provides various mechanisms by which they can be triggered.

Getting Started

Simply clone this repository like this:

git clone git@github.com:sbrl/shunction.git
cd shunction;

Then you can call shunction like this to display some quick help on how to use it:

./shunction

Functions are, by default, looked for in ./functions. A function file can be any executable with a filename in the form function_name.func - the shebang (the #!... bit) is respected.

CLI Arguments

Extra CLI arguments are supported:

Argument	Short form	Meaning
--config	-c	Specify the location of a configuration file to load
--strip-ansi	none	Strip all ANSI escape codes from the output. Useful for sending the output to a log file etc.

Configuration

Although not required, shunction can take a configuration file. Specify it's location with the --config CLI argument.

Such a configuration file should look something like this:

#!/usr/bin/env bash
functions_folder="path/to/directory";

Directive	Default Value	Meaning
functions_folder	./functions	The location of the directory in which to find functions to execute
strip_ansi	false	Whether to strip all ANSI escape codes from the output. Useful for sending the output to a log file.

Usage

Shunction supports 4 modes of operation: ad-hoc, cron, inotify, and http.

Ad-hoc

For one-off runs, use ad-hoc mode.

./shunction trigger adhoc function_name

Cron

Regularly-repeating jobs can be invoked by editing your crontab with crontab -e. Paste in something like this:

5 4 * * *	/absolute/path/to/shunction trigger cron function_name

This website is really useful for generating crontab definitions: https://crontab.guru/.

Inotify

The inotify mode allows you to run jobs when something changes on disk. The inotifywait command is required. Shunction will automatically watch subdirectories for you.

Use it like this:

./shunction inotify "path/to/file/or/directory" "function_name"

It will stick around until it is killed. Note that it will run the function once for every event detected in the background and start listening for additional jobs immediately, so if you need to ensure only 1 instance of your program is running, try looking at this StackOverflow answer.

Http

Finally, shunction supports listening over HTTP, though it's not advised to listen on anything more than localhost. Unlike inotify, http mode supports execution of multiple different functions, though only 1 at a time.

./shunction http bind_address port_number
./shunction http 127.0.0.1 7777

Note that regular Linux rules still apply - if you want to listen on port numbers below 1024, shunction either needs to run as root (bad idea!), or you need to tell Linux that it's allowed to like this: setcap 'cap_net_bind_service=+ep' path/to/shunction.