@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

``bash
bun add @procwire/bun-core
`

Requirements: Bun >= 1.0

Dependencies: @procwire/protocol, @procwire/codecs

Quick Start

`typescript
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

$3

Fluent builder for defining a worker module.

`typescript
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.

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

#### .method(name, config)

Register a method the worker can handle.

`typescript
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.

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

#### .spawnPolicy(policy)

Configure spawn and restart behavior.

`typescript
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
});
`

$3

#### module.send(method, data, options?)

Send a request and wait for response.

`typescript
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.

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

#### module.onEvent(name, callback)

Listen to events from the worker.

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

$3

Orchestrates module lifecycle.

`typescript
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
`

$3

`typescript
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
`

$3

| 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) |

$3

`typescript
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");
`

$3

`typescript
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:

`diff
-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