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trigger + triggerd

Simplistic UDP-based scheduler with a single slot queue.

I hope that you find trigger + triggerd useful 💚💜

Installation

Example

$ triggerd make &

$ trigger # Schedule a build
$ trigger # Schedule another build
          # (Make will be restarted upon completion)
$ trigger # Attempt to schedule yet another build
          # (has no effect if Make is still running)

Overview

triggerd listens on IPv6 loopback UDP port 51161 (overridable by setting TRIGGERD_PORT environment variable).

When triggerd receives a packet, it executes a program from its command-line arguments. While this program keeps running, there is a single slot that can take another packet. If the slot is taken by the time the program exits, it will be immediately restarted. Once the slot is taken, additional received packets have no effect until the program is restarted and the slot is emptied.

trigger sends a packet to triggerd.

For details, consult trigger(1) and triggerd(8) man pages.

Attribution

Prototype sponsored by Serokell.

Clone Rounded PE logo font by Lasko Džurovski from Rosetta Type Foundry.

On/off switch logo icon by Tanya Nevskaya.

Social preview background pattern by Steve Schoger from Hero Patterns, licensed under CC BY 4.0.

trigger + triggerd were designed for continuous deployment on NixOS: triggerd nixos-rebuild switch rebuilds the system on request while deduplicating consecutive rebuild requests; trigger requests a system rebuild.

One caveat to be aware of: all users on a system typically have access to UDP. Do not use triggerd with anything that can lead to privilege escalation. If internal denial-of-service is a concern for you, set up a firewall policy that limits triggerd port access to a trusted group.