How do you implement a custom process manager in Node.js?

Question

Accepted Answer

**Process manager** — monitor and restart crashed processes.

```javascript
const { fork } = require("child_process");

class ProcessManager {
    constructor() {
        this.processes = new Map();
    }

start(name, script, options = {}) {
        const { maxRestarts = 5, restartDelay = 1000 } = options;
        let restarts = 0;

const spawn = () => {
            const child = fork(script);

child.on("exit", (code) => {
                console.log(`${name} exited with code ${code}`);
                this.processes.delete(name);

if (restarts < maxRestarts && code !== 0) {
                    restarts++;
                    console.log(`Restarting ${name} (${restarts}/${maxRestarts})...`);
                    setTimeout(spawn, restartDelay);
                }
            });

child.on("error", (err) => {
                console.error(`${name} error:`, err);
            });

this.processes.set(name, {
                child,
                restarts,
                startedAt: Date.now(),
            });
        };

spawn();
    }

stop(name) {
        const proc = this.processes.get(name);
        if (proc) {
            proc.child.kill();
            this.processes.delete(name);
        }
    }

status() {
        const status = {};
        this.processes.forEach((proc, name) => {
            status[name] = {
                pid: proc.child.pid,
                restarts: proc.restarts,
                uptime: Date.now() - proc.startedAt,
            };
        });
        return status;
    }
}

// Usage
const pm = new ProcessManager();
pm.start("api", "./server.js", { maxRestarts: 3 });
pm.start("worker", "./worker.js");
console.log(pm.status());
```

Node.js: How do you implement a custom process manager in Node.js?