parax

parallel exec

parax runs multiple commands in parallel from a JSON descriptor file. It supports restarting crashed processes, delayed starts, and a built-in web server that tracks restart counts.

Installation

npm install --global parax

Usage

parax commands.json

Descriptor fields

commands (required)

Array of command objects to run in parallel.

| Field | Type | Description | | ------- | -------- | ------------------------------------ | | cmd | string | The executable to run | | args | string[] | Arguments to pass to the executable | | cwd | string | Working directory for the process | | env | object | Extra environment variables | | delay | number | Milliseconds to wait before starting |

keepAlive

When true, any process that exits is automatically restarted.

loopMillis

How often (in milliseconds) parax checks process state. Defaults to 2000.

webPort

When set, starts an HTTP server on the given port exposing restart counts at GET /restarts.

Examples

Basic parallel execution:

{
    "commands": [
        { "cmd": "npm", "args": ["run", "dev"], "cwd": "./frontend" },
        { "cmd": "npm", "args": ["run", "start"], "cwd": "./backend" }
    ]
}

Keep services alive with a delayed start:

{
    "keepAlive": true,
    "commands": [
        { "cmd": "node", "args": ["db.js"] },
        { "cmd": "node", "args": ["server.js"], "delay": 2000 }
    ]
}

Track restarts via the web server:

{
    "keepAlive": true,
    "webPort": 3000,
    "commands": [
        { "cmd": "node", "args": ["worker.js"] },
        { "cmd": "node", "args": ["api.js"] }
    ]
}

GET http://localhost:3000/restarts

[
  { "cmd": "node worker.js", "restarts": 2 },
  { "cmd": "node api.js", "restarts": 0 }
]