Taskmaster

Rust process supervisor for the 42 Taskmaster project. It runs in the foreground, keeps configured jobs under supervision, logs lifecycle events, and provides an interactive control shell.

Evaluation status

The mandatory marking-sheet behaviors are implemented:

Requirement	Implementation / proof
Control shell	status, start, stop, restart, reload, exit
Config at launch	TOML loader with validation
Hot reload	Shell reload and external SIGHUP
Selective reload	Unchanged program groups keep their existing PIDs
Logging	START, STOP, RESTART, CRASH, FATAL, CONFIG_RELOAD
Required options	All options from the subject are represented below
Graceful stop	Configured signal, timeout, then SIGKILL escalation
Clean shutdown	Every attached process group is stopped before exit
Retry abort	Early failures become FATAL after startretries
Output handling	Omitted output paths discard; configured paths append

Only serde and toml are third-party dependencies. They are used exclusively for configuration parsing, as allowed by the subject. Signals, process groups, timestamps, shell parsing, and logging use the Rust standard library and small operating-system FFI declarations.

Build and run

cargo build --locked
cargo run -- config/evaluation.toml

The binary remains in the foreground:

./target/debug/taskmaster config/evaluation.toml

Control shell

status
start <program|all>
stop <program|all>
restart <program|all>
reload
history
help
quit
exit

status shows one row per configured instance with its PID, STARTING, RUNNING, STOPPED, or FATAL state, and uptime.

quit, exit, Ctrl-C, and SIGTERM stop the supervisor. Taskmaster sends each configured stop signal to the whole child process group, waits stoptime, then sends SIGKILL to any survivors. Descendants do not remain orphaned.

Hot reload

Both interfaces read the original config path again:

taskmaster> reload

kill -HUP <taskmaster-pid>

Reload is diff-based:

• unchanged programs and their PIDs are preserved;
• removed programs are stopped and removed;
• added programs are registered and started when autostart = true;
• changed programs are gracefully stopped, replaced, and restarted if they were active or are configured for autostart;
• invalid replacement files are rejected before runtime state changes.

Configuration

[programs.worker]
cmd = "while true; do echo $MESSAGE; sleep 2; done"numprocs = 2autostart = trueautorestart = "unexpected"exitcodes = [0]
startretries = 3starttime = 1stopsignal = "TERM"stoptime = 2stdout = "/tmp/worker.out"stderr = "/tmp/worker.err"log = "/tmp/worker.lifecycle.log"workingdir = "/tmp"umask = 0o027
[programs.worker.env]
MESSAGE = "managed by taskmaster"

Field	Meaning	Default
cmd	Shell command used to launch the program	required
numprocs	Instances to create and supervise	1
autostart	Start when Taskmaster launches	false
autorestart	always, never, or unexpected	never
exitcodes	Expected exit codes	[0]
startretries	Retries after early startup failures	0
starttime	Seconds required to reach RUNNING; 0 accepts immediate exit	1
stopsignal	Graceful stop signal name or number	TERM
stoptime	Seconds before SIGKILL; 0 escalates immediately	5
stdout	Append stdout to this file; omit to discard	discard
stderr	Append stderr to this file; omit to discard	discard
log	Per-program lifecycle log; omit for global log	global
env	Environment variables for the child	inherited environment
workingdir	Child working directory	Taskmaster directory
umask	Child Unix umask	inherited umask

Commands are executed through /bin/sh -c on Unix and cmd.exe /S /C on Windows. Shell built-ins such as exit 42, quoting, environment expansion, and redirections therefore work as configuration commands.

Short-lived commands

A command such as ls exits before the default one-second starttime, so it is correctly treated as a startup failure. Configure starttime = 0 for intentional one-shot commands:

[programs.oneshot]
cmd = "ls -la"starttime = 0autorestart = "never"exitcodes = [0]

NUL is not a typo

NUL is the Windows null device, equivalent to /dev/null on Unix. Taskmaster selects the correct name at compile time.

Logging

The fallback log is ./logs/taskmaster.log. A program-specific log path overrides it for that program.

Logged events:

• process start and PID;
• graceful/manual stop;
• unexpected exit or signal death;
• automatic restart and reason;
• retry exhaustion (FATAL and attempt count);
• configuration reload and source path.

Evaluator proof

Run all unit tests:

cargo test --workspace

On Linux, run the end-to-end marking-sheet smoke test:

bash scripts/evaluator_smoke.sh

It proves:

1. initial autostart;
2. external SIGHUP reload;
3. unchanged PID preservation;
4. autostart of an added program;
5. shell-command reload;
6. removal of a program;
7. accurate status output;
8. shutdown through exit;
9. no surviving supervised children.

Use config/evaluation.toml during the defense to demonstrate every required configuration option, retry exhaustion, and a short-lived command.

Project layout

• bin/main.rs: startup, signal installation, shell, shutdown
• crates/config: TOML model and validation
• crates/process: spawning, process groups, lifecycle reconciliation, selective reload
• crates/signals: SIGINT/SIGTERM/SIGHUP flags
• crates/logger: lifecycle logging
• crates/tui: interactive control shell
• scripts/evaluator_smoke.sh: end-to-end evaluator proof