@procwire/bun-core

Parent-side module system for Procwire IPC — Bun.js optimized.

Drop-in alternative to @procwire/core using Bun-native APIs (Bun.spawn(), Bun.listen(), Bun.connect()) for lower overhead and tighter runtime integration.

Highlights

• Module — Fluent builder for defining worker processes
• ModuleManager — Spawn, lifecycle management, restart policies
• Response types — result, stream, ack, none
• Automatic retry/restart on failure with configurable backoff
• AbortController cancellation support
• Bun-native I/O — Bun.spawn() + Bun.connect() instead of Node.js child_process/net
• BunDrainWaiter — backpressure handling via Bun socket drain callbacks

Installation

bun add @procwire/bun-core

Requirements: Bun >= 1.0

Dependencies: @procwire/protocol, @procwire/codecs

Quick Start

import { Module, ModuleManager } from "@procwire/bun-core";
import { msgpackCodec, arrowCodec } from "@procwire/codecs";

// Define a module
const worker = new Module("worker")
  .executable("python", ["worker.py"])
  .method("process", { codec: msgpackCodec })
  .method("batch", { codec: arrowCodec, response: "stream" })
  .event("progress");

// Spawn via manager
const manager = new ModuleManager();
manager.register(worker);
await manager.spawn();

// Single response
const result = await worker.send("process", data);

// Streaming response
for await (const chunk of worker.stream("batch", items)) {
  console.log(chunk);
}

// Listen to events
worker.onEvent("progress", (p) => console.log(`${p}%`));

// Shutdown
await manager.shutdown();

API Reference

Module

Fluent builder for defining a worker module.

const module = new Module("name")
  .executable(command, args, options?)
  .method(name, config)
  .event(name, config?)
  .spawnPolicy(policy)
  .maxPayloadSize(bytes);

.executable(command, args, options?)

Set the command to spawn the worker process.

module.executable("python", ["worker.py"], {
  cwd: "/path/to/working/dir",
  env: { CUSTOM_VAR: "value" },
});

.method(name, config)

Register a method the worker can handle.

module.method("process", {
  codec: msgpackCodec, // Serialization codec
  response: "result", // "result" | "stream" | "ack" | "none"
  timeout: 30000, // Optional timeout in ms
  cancellable: true, // Support AbortController
});

.event(name, config?)

Register an event the worker can emit.

module.event("progress", { codec: msgpackCodec });

.spawnPolicy(policy)

Configure spawn and restart behavior.

module.spawnPolicy({
  initTimeout: 30000, // Timeout for $init message
  maxRetries: 3, // Spawn retry attempts
  retryDelay: { type: "exponential", base: 1000, max: 30000 },
  restartOnCrash: true, // Auto-restart on unexpected exit
  restartLimit: { maxRestarts: 5, windowMs: 60000 },
  socketBufferSize: 4 * 1024 * 1024, // 4MB for large payloads
});

Communication

module.send(method, data, options?)

Send a request and wait for response.

const result = await module.send("process", { input: "data" });

// With cancellation
const controller = new AbortController();
const result = await module.send("process", data, {
  signal: controller.signal,
});
// controller.abort() to cancel

module.stream(method, data, options?)

Send a request and iterate over streamed chunks.

for await (const chunk of module.stream("batch", items)) {
  processChunk(chunk);
}

module.onEvent(name, callback)

Listen to events from the worker.

module.onEvent("progress", (data) => {
  console.log(`Progress: ${data.percent}%`);
});

ModuleManager

Orchestrates module lifecycle.

const manager = new ModuleManager();

// Register modules
manager.register(worker1);
manager.register(worker2);

// Spawn all or specific
await manager.spawn();           // All registered
await manager.spawn("worker1");  // Specific module

// Get module
const mod = manager.get("worker1");

// Check registration
if (manager.has("worker1")) { ... }

// Shutdown all or specific
await manager.shutdown();          // All
await manager.shutdown("worker1"); // Specific

Module States

type ModuleState =
  | "created" // Defined but not spawned
  | "initializing" // Process started, waiting for $init
  | "connecting" // Connecting data channel
  | "ready" // Fully operational
  | "disconnected" // Lost connection (may restart)
  | "closed"; // Terminated

Response Types

| Type | Description | Parent API | | -------- | ------------------- | ---------------------------------------- | | result | Single response | await module.send() | | stream | Multiple chunks | for await (... of module.stream()) | | ack | Acknowledgment only | await module.send() (returns ack data) | | none | Fire-and-forget | module.send() (returns immediately) |

Error Handling

import { ProcwireError, SpawnError, ModuleErrors, ManagerErrors } from "@procwire/bun-core";

try {
  await manager.spawn();
} catch (e) {
  if (e instanceof SpawnError) {
    console.log(`Failed after ${e.attempts} attempts`);
    console.log(`Last error: ${e.lastError}`);
  }
}

// Error factories
ModuleErrors.notReady("worker", "created");
ModuleErrors.unknownMethod("unknown");
ModuleErrors.timeout("process");

ManagerErrors.notRegistered("worker");
ManagerErrors.alreadyRegistered("worker");

Events

import { ManagerEvents, ModuleEvents } from "@procwire/bun-core";

// Manager events
manager.on(ManagerEvents.READY, (name) => console.log(`${name} ready`));
manager.on(ManagerEvents.ERROR, (name, err) => console.error(`${name} error:`, err));
manager.on(ManagerEvents.RESTARTING, (name) => console.log(`${name} restarting`));
manager.on(ManagerEvents.SPAWN_FAILED, (name, err) => console.error(`${name} spawn failed`));

// Module events
module.on(ModuleEvents.STATE, (state) => console.log(`State: ${state}`));
module.on(ModuleEvents.ERROR, (err) => console.error(err));
module.on(ModuleEvents.DISCONNECTED, () => console.log("Disconnected"));

Differences from @procwire/core

This package has the same API surface as @procwire/core but uses Bun-native primitives under the hood:

| Concern | @procwire/core (Node.js) | @procwire/bun-core (Bun) | | -------------- | ------------------------------------------ | ------------------------------------------------ | | Process spawn | child_process.spawn() | Bun.spawn() | | Socket connect | net.connect() | Bun.connect() | | Backpressure | socket.cork()/uncork() + drain event | BunDrainWaiter + socket.write() return value | | Atomic writes | cork/uncork batching | Buffer.concat() before write | | Tests | Vitest | bun:test |

Switching between runtimes requires only changing the import:

-import { Module, ModuleManager } from "@procwire/core";
+import { Module, ModuleManager } from "@procwire/bun-core";

Architecture

┌─────────────────────────────────────────────────────────────┐
│                     Parent Process (Bun)                    │
│  ┌──────────────────────────────────────────────────────┐  │
│  │                   ModuleManager                       │  │
│  │  ┌─────────────┐  ┌─────────────┐  ┌─────────────┐  │  │
│  │  │   Module    │  │   Module    │  │   Module    │  │  │
│  │  │  "worker1"  │  │  "worker2"  │  │  "worker3"  │  │  │
│  │  └──────┬──────┘  └──────┬──────┘  └──────┬──────┘  │  │
│  └─────────┼────────────────┼────────────────┼─────────┘  │
└────────────┼────────────────┼────────────────┼────────────┘
             │                │                │
    ┌────────┴───────┐ ┌──────┴──────┐ ┌───────┴──────┐
    │ Child Process  │ │ Child Proc  │ │ Child Proc   │
    │   (Python)     │ │   (Bun)     │ │   (Rust)     │
    └────────────────┘ └─────────────┘ └──────────────┘

Communication channels:

• Control Plane (stdio): JSON-RPC 2.0 — handshake, heartbeat
• Data Plane (named pipe): Binary protocol — user data

License

MIT