feat(runtime): add GET /ready readiness probe for graceful rolling restarts (#2217)

The dispatcher exposed only /health (always 200). Multi-replica deployments
need a readiness signal so a load balancer drains a replica before its
in-flight requests are force-closed on shutdown. /ready returns 200 only when
the kernel state is 'running'; 503 while booting (idle/initializing) or
shutting down (stopping/stopped). Added to the membership-skip paths like
/health so it is reachable without auth/environment scoping.

Pairs with the existing in-flight drain in HonoHttpServer.close() (P1-3).

Co-authored-by: Jack Zhuang <277994282+os-zhuang@users.noreply.github.com>
Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

Author: 3 people

packages/runtime/src/http-dispatcher.ready.test.ts

@@ -0,0 +1,27 @@
+import { describe, it, expect } from 'vitest';
+import { HttpDispatcher } from './http-dispatcher.js';
+
+function kernel(state: string): any {
+  return {
+    getState: () => state,
+    getService: () => undefined,
+    getServiceAsync: async () => undefined,
+  };
+}
+const ctx: any = {};
+
+describe('HttpDispatcher — GET /ready readiness probe', () => {
+  it('returns 200 when the kernel is running', async () => {
+    const res = await new HttpDispatcher(kernel('running')).dispatch('GET', '/ready', undefined, undefined, ctx);
+    expect(res.handled).toBe(true);
+    expect(res.response.status).toBe(200);
+    expect(res.response.body.data.state).toBe('running');
+  });
+
+  it('returns 503 while booting or shutting down', async () => {
+    for (const state of ['idle', 'initializing', 'stopping', 'stopped']) {
+      const res = await new HttpDispatcher(kernel(state)).dispatch('GET', '/ready', undefined, undefined, ctx);
+      expect(res.response.status).toBe(503);
+    }
+  });
+});

packages/runtime/src/http-dispatcher.ts

@@ -699,7 +699,7 @@ export class HttpDispatcher {
         if (!this.enforceMembership) return null;
 
         // Control-plane paths — never gated by project membership.
-        const skipPaths = ['/auth', '/cloud', '/health', '/discovery'];
+        const skipPaths = ['/auth', '/cloud', '/health', '/ready', '/discovery'];
         if (skipPaths.some(p => path.startsWith(p))) return null;
 
         // Public share-link resolve/messages — the token IS the authorisation,
@@ -3076,6 +3076,20 @@ export class HttpDispatcher {
             };
         }
 
+        // 0b2. Readiness Endpoint (GET /ready) — k8s / load-balancer readiness probe.
+        // 200 only when the kernel is fully running; 503 while booting
+        // (idle/initializing) or shutting down (stopping/stopped) so a load
+        // balancer stops routing to this replica BEFORE in-flight requests are
+        // drained and the server closes (graceful rolling restart).
+        if (cleanPath === '/ready' && method === 'GET') {
+            const state: string = typeof (this.kernel as any)?.getState === 'function'
+                ? (this.kernel as any).getState()
+                : 'running';
+            return state === 'running'
+                ? { handled: true, response: this.success({ status: 'ready', state }) }
+                : { handled: true, response: this.error('Service not ready', 503, { state }) };
+        }
+
         // 0c. Plan-A diagnostics removed; the seed-replay and oauth2/callback
         // probes were temporary debugging tools used during the SSO rollout.