finit/TODO.md

TODO

Unsorted TODO list of features and points of investigation that could be useful for improving finit. But what is an improvement to finit? Well, similiar to launchd, the goal of finit is to be a FAST replacement for:

• init
• inetd
• crond
• watchdogd

The main goal is to be FAST. Secondary goals are to be: small, simple and with a very low dependency on external packages.

Inetd

Simple way of running Internet services on demand, like the old inetd:

inetd SVC [RUNLVL] /path/to/daemon args -- description

Example:

# Inetd services, launched on demand
inetd ssh [2345] /usr/sbin/sshd -i -- SSH Daemon

In keeping with the finit tradition, an optional callback can be setup to each inetd service. When a client connects the finit will call the callback with a struct in_pktinfo argument which the callback then can allowed or deny.

Priority

The intent of finit is to monitor not just processes, but also to be able to supervise the entire system and the behavior of certain processes that declare themselves to be finit compliant.

• Integrate the ingenious libev to handle all events: signals, polling fd's, etc. Because "Event driven software improves concurrency" -- Dave Zarzycki, Apple.

  See the launchd video for more info!

• Add support for a /dev/watchdog plugin to replace watchdogd

• Integrate watchdog plugin with process/system supervisor to optionally reboot the system when a process stops responding, or when a respawn limit has been reached, as well as when system load gets too high.

Configuration

• Add support for init <q | reload-configuration> and SIGHUP to have finit reload its finit.conf, but also

• Add support for inotify to automatically reload finit.conf

Runlevels

• Add support for runlevel N to finit.conf

• Improve support for runlevels: startup, running (services from finit.conf), and shutdown as well as hooks when switching RL, startup at RL 1 and a default run level.

• Implement initctl stop|start|restart|reload|status <SVC> and service <SVC> stop|start|restart|reload|status on top

• Add PRE and POST hooks for when changing runlevels

• SysV init in Debian uses an rcS.d/ for scripts that should run once at boot. These scripts are run before the actual runlevel, which is set in inittab(5). We could use task [S] and run [S] (below) for this.

• Add support for a new runlevel 'S' that is started before all other services in the selected runlevel.

Services and Tasks

Both the task and boot stanzas below are like service, share the same mechanism for registering callbacks. These callbacks can be used to check a configuration db and return 1 (RUN), 2 (STOP), or 3 (RELOAD).

• Add support for task [RUNLVL] ... similar to services, but one-shot.
• Add support for run [RUNLVL] ... similar to task, but waits for completion before continuing with the next task/service
• Add support for service/task/run dependencies
• Add support for init list to show running services

It is tempting to say that a task called at runlevel S would be a blocking call, like run, but there are likely use-cases when you want to call on-shot tasks in parallel with something else, even at boot. Hence the differentiation between "task" and "run", which are essentially the same, except for the "pause and wait for completion" that "run" has.

Miscellaneous

• Add support for init -v,--version | version
• Cleanup move sources from top-level directory to src/ and include/
• Make sure to install queue.h to $(PREFIX)/include/finit/queue.h
• Move finit.conf "check" command to plugin which checks /etc/fstab instead. This is the de-facto practice. But keep the check command for really low-end systems w/o /etc/fstab.

Documentation

• Write man pages for finit and finit.conf, steal from the excellent pimd man pages ...
• Update Debian finit.conf example with runlevels, tty/console and dependency handling

Investigation

• FHS changes affecting runtime status, plugins, etc.