Add polyglot-coordination example with Python, Node.js, and Rust

.gitignore

@@ -9,6 +9,14 @@ dist/
 *.mjs
 !tsconfig.json
 
+# Rust
+target/
+Cargo.lock
+
+# Lock files
+pnpm-lock.yaml
+package-lock.json
+
 # IDE
 .idea/
 .vscode/

README.md

@@ -24,6 +24,7 @@ iii --version
 | [api-frameworks-workers](examples/api-frameworks-workers) | Run 4 API frameworks as separate workers |
 | [api-frameworks-auto-register](examples/api-frameworks-auto-register) | Auto-registration + shared context (logging, state, request tracking) |
 | [iii-vs-traditional](examples/iii-vs-traditional) | Side-by-side: connect a Python service with iii (~120 lines) vs traditional gateway (~465 lines) |
+| [polyglot-coordination](examples/polyglot-coordination) | Coordinate Python, Node.js, and Rust services (Python via stdin/stdout IPC, Rust via HTTP) |
 
 ## Quick Start
 

examples/polyglot-coordination/.gitignore

@@ -0,0 +1,11 @@
+node_modules/
+dist/
+*.js
+*.d.ts
+.DS_Store
+.env
+.env.local
+__pycache__/
+*.pyc
+target/
+Cargo.lock

examples/polyglot-coordination/README.md

@@ -0,0 +1,201 @@
+# Polyglot Coordination Example
+
+This example demonstrates **iii-engine** seamlessly coordinating services across **Python, Node.js, and Rust** without requiring HTTP endpoints for all services.
+
+**Key differentiator**: The Python service communicates via **stdin/stdout IPC** (not HTTP), showing that iii abstracts away transport mechanisms entirely.
+
+## Architecture
+
+```mermaid
+flowchart TB
+    subgraph Client
+        API[curl / HTTP Client]
+    end
+
+    subgraph iii[iii-engine]
+        ENGINE[WebSocket Hub<br/>ws://127.0.0.1:49134]
+    end
+
+    subgraph Workers[Node.js Workers]
+        USER[User Service<br/>users.*]
+        DATA[Data Requester<br/>analytics.*]
+        STRIPE_BRIDGE[Stripe Bridge<br/>stripe.*]
+    end
+
+    subgraph Services[External Services]
+        PYTHON[Python Analytics<br/>stdin/stdout IPC<br/>NO HTTP]
+        RUST[Rust Fake Stripe<br/>HTTP :4040]
+    end
+
+    API -->|POST /onboard| ENGINE
+    ENGINE <-->|WebSocket| USER
+    ENGINE <-->|WebSocket| DATA
+    ENGINE <-->|WebSocket| STRIPE_BRIDGE
+    DATA -->|spawns & IPC| PYTHON
+    STRIPE_BRIDGE -->|HTTP calls| RUST
+
+    style PYTHON fill:#3776ab,color:#fff
+    style RUST fill:#dea584,color:#000
+    style ENGINE fill:#6366f1,color:#fff
+    style USER fill:#22c55e,color:#fff
+    style DATA fill:#22c55e,color:#fff
+    style STRIPE_BRIDGE fill:#22c55e,color:#fff
+```
+
+## Business Scenario: SaaS User Onboarding
+
+A realistic workflow tying all 3 languages together:
+
+1. **New user signs up** → Node.js User Service
+2. **Create Stripe customer + subscription** → Rust Fake Stripe (via HTTP, wrapped by iii)
+3. **Run onboarding analytics** → Python Analytics (via stdin/stdout IPC)
+4. **Store user profile with risk score** → Orchestrated by Node.js Workflow
+
+## Prerequisites
+
+- **Node.js 18+** or **Bun** (for workers)
+- **Python 3.x** (stdlib only, no pip install needed)
+- **Rust toolchain** (for Axum server)
+- **iii-engine** running (`iii` command)
+
+## Quick Start
+
+### Terminal 1: Start iii-engine
+```bash
+iii
+```
+
+### Terminal 2: Start Rust Fake Stripe server
+```bash
+cd services/rust-stripe
+cargo run --release
+```
+
+### Terminal 3: Install deps and start workers
+```bash
+pnpm install
+pnpm dev
+```
+
+## Testing
+
+### Full onboarding flow (coordinates all 3 languages)
+```bash
+curl -X POST http://localhost:3111/onboard \
+  -H "Content-Type: application/json" \
+  -d '{"email": "alice@example.com", "name": "Alice Smith", "plan": "pro"}'
+```
+
+Expected response:
+```json
+{
+  "message": "User onboarded successfully",
+  "traceId": "abc123...",
+  "user": {
+    "id": "usr_...",
+    "email": "alice@example.com",
+    "name": "Alice Smith",
+    "plan": "pro",
+    "stripeCustomerId": "cus_...",
+    "subscriptionId": "sub_...",
+    "riskScore": 45.5
+  },
+  "stripeCustomer": { "id": "cus_...", "email": "...", "name": "..." },
+  "subscription": { "id": "sub_...", "status": "active", "plan": "pro" },
+  "analytics": { "riskScore": 45.5, "factors": ["custom_domain", "full_name_provided"] }
+}
+```
+
+### Get metrics (calls Python analytics)
+```bash
+curl http://localhost:3111/onboard/metrics
+```
+
+### Onboard multiple users and check metrics
+```bash
+curl -X POST http://localhost:3111/onboard \
+  -d '{"email": "bob@gmail.com", "name": "Bob", "plan": "free"}' \
+  -H "Content-Type: application/json"
+
+curl -X POST http://localhost:3111/onboard \
+  -d '{"email": "carol@stanford.edu", "name": "Carol Chen", "plan": "enterprise"}' \
+  -H "Content-Type: application/json"
+
+curl http://localhost:3111/onboard/metrics
+```
+
+## Key Insight
+
+All function calls look identical regardless of transport:
+
+```typescript
+// Calls Rust via HTTP (wrapped by stripe-bridge)
+await bridge.invokeFunction('stripe.createCustomer', { email, name })
+
+// Calls Python via stdin/stdout IPC (wrapped by data-requester)
+await bridge.invokeFunction('analytics.score', { userId, email, name })
+
+// Calls local Node.js function
+await bridge.invokeFunction('users.create', { email, name })
+```
+
+**The caller doesn't know or care about the underlying transport. That's the power of iii.**
+
+## File Structure
+
+```
+polyglot-coordination/
+├── README.md
+├── package.json
+├── tsconfig.json
+├── services/
+│   ├── python-analytics/
+│   │   └── analytics.py           # stdin/stdout JSON-RPC (NO HTTP)
+│   └── rust-stripe/
+│       ├── Cargo.toml
+│       └── src/main.rs            # Axum HTTP server
+├── workers/
+│   ├── user-service.ts            # User CRUD + billing
+│   ├── data-requester.ts          # Spawns Python, exposes analytics.*
+│   └── stripe-bridge.ts           # Wraps Rust HTTP as iii functions
+├── workflow/
+│   └── onboarding.ts              # Orchestrates full signup flow
+└── lib/
+    ├── bridge.ts                  # Shared bridge factory
+    ├── python-ipc.ts              # Python subprocess manager
+    └── types.ts                   # Shared TypeScript types
+```
+
+## How It Works
+
+### Python Analytics (stdin/stdout)
+The Python service has **no HTTP endpoints**. It reads JSON from stdin, processes it, and writes JSON to stdout:
+
+```python
+for line in sys.stdin:
+    request = json.loads(line)
+    result = handle_request(request['method'], request['params'])
+    sys.stdout.write(json.dumps({'id': request['id'], 'result': result}) + '\n')
+```
+
+The `data-requester.ts` worker spawns this script and communicates via stdin/stdout, then exposes the functionality as iii functions.
+
+### Rust Fake Stripe (HTTP)
+A standard Axum HTTP server providing a Stripe-like API. The `stripe-bridge.ts` worker makes HTTP calls to it and exposes the endpoints as iii functions.
+
+### Node.js User Service
+Pure Node.js with in-memory storage, directly registered as iii functions.
+
+## Why This Matters
+
+Traditional microservice orchestration requires:
+- Every service to expose HTTP/gRPC endpoints
+- Service discovery (Consul, etcd, K8s DNS)
+- Load balancers, ingress controllers
+- API gateways for routing
+
+With iii-engine:
+- Services can use **any transport** (HTTP, IPC, stdin/stdout, sockets)
+- iii handles routing via **function names**
+- No service discovery needed - iii is the registry
+- No API gateway - iii exposes triggers directly

examples/polyglot-coordination/lib/bridge.ts

@@ -0,0 +1,14 @@
+import { Bridge } from '@iii-dev/sdk'
+
+const ENGINE_URL = process.env.III_ENGINE_URL ?? 'ws://127.0.0.1:49134'
+
+export function createBridge(serviceName: string): Bridge {
+  return new Bridge(ENGINE_URL, {
+    otel: {
+      enabled: true,
+      serviceName,
+      metricsEnabled: true,
+      metricsExportIntervalMs: 5000,
+    },
+  })
+}

examples/polyglot-coordination/lib/python-ipc.ts

@@ -0,0 +1,135 @@
+import { spawn, type ChildProcess } from 'child_process'
+import { createInterface, type Interface } from 'readline'
+import { EventEmitter } from 'events'
+import { existsSync } from 'fs'
+
+interface PendingRequest {
+  resolve: (result: unknown) => void
+  reject: (error: Error) => void
+  timeout: ReturnType<typeof setTimeout>
+}
+
+const PYTHON_PATH = process.env.PYTHON_PATH ?? 'python3'
+
+export class PythonIPC extends EventEmitter {
+  private process: ChildProcess | null = null
+  private readline: Interface | null = null
+  private requestId = 0
+  private pending = new Map<number, PendingRequest>()
+  private ready = false
+  private readyPromise: Promise<void>
+  private readyResolve!: () => void
+
+  constructor(
+    private scriptPath: string,
+    private timeoutMs = 30000,
+    private maxPendingRequests = 1000
+  ) {
+    super()
+    this.readyPromise = new Promise((resolve) => {
+      this.readyResolve = resolve
+    })
+  }
+
+  async start(): Promise<void> {
+    if (!existsSync(this.scriptPath)) {
+      throw new Error(`Python script not found: ${this.scriptPath}`)
+    }
+
+    this.process = spawn(PYTHON_PATH, [this.scriptPath], {
+      stdio: ['pipe', 'pipe', 'pipe'],
+    })
+
+    this.readline = createInterface({
+      input: this.process.stdout!,
+      crlfDelay: Infinity,
+    })
+
+    this.readline.on('line', (line) => this.handleLine(line))
+
+    this.process.stderr?.on('data', (data) => {
+      const msg = data.toString().trim()
+      if (msg) console.error(`[Python stderr] ${msg}`)
+    })
+
+    this.process.on('close', (code) => {
+      this.ready = false
+      this.emit('close', code)
+      for (const [id, req] of this.pending) {
+        clearTimeout(req.timeout)
+        req.reject(new Error(`Python process exited with code ${code}`))
+        this.pending.delete(id)
+      }
+    })
+
+    this.process.on('error', (err) => {
+      this.emit('error', err)
+    })
+
+    await this.call('ping', {})
+    this.ready = true
+    this.readyResolve()
+  }
+
+  async waitReady(): Promise<void> {
+    return this.readyPromise
+  }
+
+  async call<T = unknown>(method: string, params: unknown): Promise<T> {
+    if (!this.process || !this.process.stdin) {
+      throw new Error('Python process not started')
+    }
+
+    if (this.pending.size >= this.maxPendingRequests) {
+      throw new Error(`Too many pending requests (max: ${this.maxPendingRequests})`)
+    }
+
+    const id = ++this.requestId
+    if (this.requestId > Number.MAX_SAFE_INTEGER - 1) {
+      this.requestId = 0
+    }
+    const request = JSON.stringify({ id, method, params })
+
+    return new Promise((resolve, reject) => {
+      const timeout = setTimeout(() => {
+        this.pending.delete(id)
+        reject(new Error(`Request ${method} timed out after ${this.timeoutMs}ms`))
+      }, this.timeoutMs)
+
+      this.pending.set(id, { resolve: resolve as (r: unknown) => void, reject, timeout })
+      this.process!.stdin!.write(request + '\n')
+    })
+  }
+
+  private handleLine(line: string): void {
+    try {
+      const response = JSON.parse(line)
+      const { id, result, error } = response
+
+      const req = this.pending.get(id)
+      if (!req) return
+
+      clearTimeout(req.timeout)
+      this.pending.delete(id)
+
+      if (error) {
+        req.reject(new Error(error.message || error))
+      } else {
+        req.resolve(result)
+      }
+    } catch {
+      console.error(`[Python IPC] Failed to parse: ${line}`)
+    }
+  }
+
+  stop(): void {
+    if (this.process) {
+      this.process.kill()
+      this.process = null
+    }
+    if (this.readline) {
+      this.readline.close()
+      this.readline = null
+    }
+  }
+}