Taskmaster

.NET 8 Job Control Daemon

Taskmaster is a lightweight process supervisor inspired by Supervisor. It launches, monitors, and manages multiple programs defined in YAML, with support for automatic restarts, configurable policies, and multiple control interfaces.

Table of Contents

• Features
• Architecture
• Installation
• Configuration
• Usage
  • Interactive Shell
  • TCP Control Interface
  • HTTP REST API
• Building & Running
• Demo Script
• Evaluation Tips
• License

Features

• YAML-based program definitions
• Automatic process supervision with restart policies (always, never, unexpected)
• Configurable options: cmd, numprocs, autostart, exitcodes, starttime, startretries, stopsignal, stoptime, stdout/stderr redirection, environment vars, workingdir, umask
• Multiple control interfaces:
  • Interactive shell with history and editing
  • TCP control server on 127.0.0.1:9090
  • HTTP/JSON API on http://localhost:8080/api
• Graceful reload and shutdown via signals or commands
• Cross-platform support (Windows/Unix)
• Logging to file and colored console output

Architecture

1. ConfigurationManager: loads and validates taskmaster.yaml.
2. TaskmasterDaemon: orchestrates startup, signal handlers, monitoring loop, and control servers.
3. ProcessManager: spawns and tracks ProcessInfo instances, enforces restart/back-off logic.
4. CommandShell: REPL with advanced ReadLineWithHistory().
5. Control Servers: TCP on port 9090 and HTTP API on port 8080.

Installation

Clone the repository:

git clone https://github.com/youruser/taskmaster.git
cd taskmaster

Configuration

Edit taskmaster.yaml to define your programs:

programs:
  webapp:
    cmd: "dotnet run --project WebApp"
    numprocs: 2
    autostart: true
    autorestart: unexpected
    exitcodes: [0]
    starttime: 5
    startretries: 3
    stopsignal: TERM
    stoptime: 10
    stdout: logs/webapp.stdout
    stderr: logs/webapp.stderr
    env:
      ASPNETCORE_ENVIRONMENT: Production
      CONNECTION_STRING: "Server=..."

Usage

Interactive Shell

dotnet run -- -c taskmaster.yaml
taskmaster> status
taskmaster> start webapp
taskmaster> reload
taskmaster> shutdown

Use arrow keys for command history and editing.

TCP Control Interface

telnet 127.0.0.1 9090
> status
> start webapp
> exit

HTTP REST API

# Get status JSON
curl http://localhost:8080/api/status

# Control a program
curl -X POST http://localhost:8080/api/programs/webapp/start

# Reload configuration
curl -X POST http://localhost:8080/api/reload

# Shutdown daemon
curl -X POST http://localhost:8080/api/shutdown

Building & Running

Build in Release mode:

dotnet build -c Release

Run with custom config:

dotnet run -- -c path/to/taskmaster.yaml

Run in background (daemon) mode:

dotnet run -- -d

Demo Script

1. Launch Taskmaster

   dotnet run -- -c taskmaster.yaml

   • In the shell, confirm autostarted programs:

     taskmaster> status

2. Simulate a Failure & Observe Restart

   • In another terminal, note a running PID:

     taskmaster> status

   • Kill that process:

     # Unix
     kill <pid>
     # Windows
     taskkill /PID <pid> /F

   • Back in Taskmaster shell, verify automatic restart:

     taskmaster> status

3. Interactive Shell Tasks

   taskmaster> stop webapp
   taskmaster> start webapp
   taskmaster> restart worker

4. TCP Control Interface

   telnet 127.0.0.1 9090

   Inside the session:

   > status
   > stop webapp
   > start webapp
   > exit
   

5. HTTP/JSON API Calls

   # Get full status
   curl http://localhost:8080/api/status
   
   # Restart a program
   curl -X POST --data "" http://localhost:8080/api/programs/simple-web/restart

6. Reload Configuration Without Downtime

   • Edit taskmaster.yaml (e.g. change worker.numprocs from 1 to 2).
   • Save the file.
   • Trigger reload in shell or via HTTP:

     taskmaster> reload
     # or
     curl -X POST http://localhost:8080/api/reload

   • Confirm new instances:

     taskmaster> status

7. Signal Handling

   • Reload via SIGHUP (Unix):

     kill -HUP <daemon_pid>

   • Dump status via SIGUSR1:

     kill -USR1 <daemon_pid>

   • Check the log file for the status dump entry.

8. Graceful Shutdown

   • From the shell:

     taskmaster> shutdown

   • Or send Ctrl+C in the console, or via HTTP:

     curl -X POST http://localhost:8080/api/shutdown

Evaluation Tips

• Slides: diagram flow (Config → Daemon → ProcessManager → Interfaces).
• Key code walkthrough: Program.cs, TaskmasterDaemon.cs, ProcessManager.cs, CommandShell.cs.
• Live demo: follow the Demo Script above.
• Be prepared to discuss restart logic, back-off, non-disruptive reload, and cross-platform signal handling.

License

MIT