Handle upstream stream drops

src/gateway.ts

@@ -28,6 +28,10 @@ export interface GatewayOptions {
   agents?: EnabledAgent[];
   /** Override the bearer token (otherwise read from ~/.a2a/credentials.json). */
   token?: string | null;
+  /** Test/advanced override for one-shot upstream JSON-RPC calls. */
+  upstreamRequestTimeoutMs?: number;
+  /** Test/advanced override for idle SSE upstream tools/call streams. */
+  upstreamStreamIdleTimeoutMs?: number;
   /** Optional override for the underlying MCP Server (tests). */
   server?: Server;
 }
@@ -56,6 +60,8 @@ export async function buildGateway(opts: GatewayOptions = {}): Promise<GatewayHa
       new UpstreamAgent({
         name: a.name, url: a.url, token,
         cpJwt, cpUrl, bucket,
+        requestTimeoutMs: opts.upstreamRequestTimeoutMs,
+        streamIdleTimeoutMs: opts.upstreamStreamIdleTimeoutMs,
       }),
     );
   }

src/upstream.ts

@@ -7,11 +7,15 @@
  * header without coupling to a transport class.
  */
 const JSON_RPC = "2.0";
+const DEFAULT_RPC_TIMEOUT_MS = 30_000;
+const DEFAULT_STREAM_IDLE_TIMEOUT_MS = 120_000;
 
 export interface UpstreamConfig {
   name: string;
   url: string;
   token: string | null;
+  requestTimeoutMs?: number;
+  streamIdleTimeoutMs?: number;
   /** Forwarded to the upstream as ``params._meta.cp_jwt`` on tools/call.
    *  Lets the upstream agent act on the caller's behalf (file/agent CRUD
    *  on /v1/me/*) — same path the platform orchestrator uses. */
@@ -63,16 +67,25 @@ export class UpstreamAgent {
 
   private async rpc<T>(method: string, params: unknown): Promise<T> {
     const id = _nextId++;
+    const timeoutMs = this.cfg.requestTimeoutMs ?? DEFAULT_RPC_TIMEOUT_MS;
+    const controller = new AbortController();
+    let timedOut = false;
+    const timeout = setTimeout(() => {
+      timedOut = true;
+      controller.abort();
+    }, timeoutMs);
     const headers: Record<string, string> = {
       "content-type": "application/json",
       accept: "application/json",
     };
     if (this.cfg.token) headers["authorization"] = `Bearer ${this.cfg.token}`;
 
+    try {
       const resp = await fetch(`${this.cfg.url}/mcp`, {
         method: "POST",
         headers,
         body: JSON.stringify({ jsonrpc: JSON_RPC, id, method, params }),
+        signal: controller.signal,
       });
 
       if (!resp.ok) {
@@ -89,6 +102,18 @@ export class UpstreamAgent {
         );
       }
       return env?.result as T;
+    } catch (err) {
+      if (timedOut) {
+        throw new UpstreamError(
+          this.cfg.name,
+          504,
+          `request timed out after ${timeoutMs}ms`,
+        );
+      }
+      throw err;
+    } finally {
+      clearTimeout(timeout);
+    }
   }
 
   async listTools(): Promise<UpstreamTool[]> {
@@ -136,22 +161,51 @@ export class UpstreamAgent {
     }) => void | Promise<void>,
   ): Promise<UpstreamCallResult> {
     const id = _nextId++;
+    const idleTimeoutMs =
+      this.cfg.streamIdleTimeoutMs ?? DEFAULT_STREAM_IDLE_TIMEOUT_MS;
+    const controller = new AbortController();
+    let timedOut = false;
+    let idleTimer: ReturnType<typeof setTimeout> | undefined;
+    const resetIdleTimer = () => {
+      if (idleTimer) clearTimeout(idleTimer);
+      idleTimer = setTimeout(() => {
+        timedOut = true;
+        controller.abort();
+      }, idleTimeoutMs);
+    };
+    resetIdleTimer();
     const headers: Record<string, string> = {
       "content-type": "application/json",
       accept: "text/event-stream, application/json",
     };
     if (this.cfg.token) headers["authorization"] = `Bearer ${this.cfg.token}`;
 
-    const resp = await fetch(`${this.cfg.url}/mcp`, {
+    let resp: Response;
+    try {
+      resp = await fetch(`${this.cfg.url}/mcp`, {
         method: "POST",
         headers,
         body: JSON.stringify({
           jsonrpc: JSON_RPC, id, method: "tools/call", params,
         }),
+        signal: controller.signal,
       });
+    } catch (err) {
+      clearTimeout(idleTimer);
+      if (timedOut) {
+        throw new UpstreamError(
+          this.cfg.name,
+          504,
+          `stream idle timeout after ${idleTimeoutMs}ms`,
+        );
+      }
+      throw err;
+    }
+    resetIdleTimer();
 
     if (!resp.ok) {
       const text = await resp.text().catch(() => "");
+      clearTimeout(idleTimer);
       throw new UpstreamError(this.cfg.name, resp.status, text || resp.statusText);
     }
 
@@ -160,15 +214,18 @@ export class UpstreamAgent {
       // Server fell back to JSON (older a2a-pack or non-SSE upstream).
       const env: any = await resp.json();
       if (env?.error) {
+        clearTimeout(idleTimer);
         throw new UpstreamError(
           this.cfg.name, 500,
           `${env.error.code}: ${env.error.message}`,
         );
       }
+      clearTimeout(idleTimer);
       return env?.result as UpstreamCallResult;
     }
 
     if (!resp.body) {
+      clearTimeout(idleTimer);
       throw new UpstreamError(this.cfg.name, 502, "empty stream body");
     }
 
@@ -177,8 +234,24 @@ export class UpstreamAgent {
     let buf = "";
     try {
       while (true) {
-        const { done, value } = await reader.read();
+        let done: boolean;
-        if (value) buf += decoder.decode(value, { stream: true });
+        let value: Uint8Array | undefined;
+        try {
+          ({ done, value } = await reader.read());
+        } catch (err) {
+          if (timedOut) {
+            throw new UpstreamError(
+              this.cfg.name,
+              504,
+              `stream idle timeout after ${idleTimeoutMs}ms`,
+            );
+          }
+          throw err;
+        }
+        if (value) {
+          resetIdleTimer();
+          buf += decoder.decode(value, { stream: true });
+        }
         let sep = buf.indexOf("\n\n");
         while (sep !== -1) {
           const frame = buf.slice(0, sep);
@@ -189,6 +262,10 @@ export class UpstreamAgent {
           }
           if (dataLines.length > 0) {
             const raw = dataLines.join("\n");
+            if (raw === "[DONE]") {
+              sep = buf.indexOf("\n\n");
+              continue;
+            }
             let msg: any;
             try { msg = JSON.parse(raw); } catch { msg = null; }
             if (msg && msg.id === id) {
@@ -221,6 +298,7 @@ export class UpstreamAgent {
         if (done) break;
       }
     } finally {
+      clearTimeout(idleTimer);
       try { reader.releaseLock(); } catch { /* ignore */ }
     }
     throw new UpstreamError(this.cfg.name, 502, "stream ended without result");

tests/gateway.test.ts

@@ -9,7 +9,7 @@ import {
   ListToolsRequestSchema,
 } from "@modelcontextprotocol/sdk/types.js";
 
-import { buildGateway, SEP } from "../src/gateway.js";
+import { buildGateway, SEP, type GatewayOptions } from "../src/gateway.js";
 import type { EnabledAgent } from "../src/config.js";
 
 /**
@@ -70,25 +70,65 @@ function startFakeAgent(opts: {
   });
 }
 
+function startSseAgent(opts: {
+  onCall: (body: any, res: http.ServerResponse) => void;
+}): Promise<{ url: string; close: () => Promise<void>; requests: any[] }> {
+  const requests: any[] = [];
+  return new Promise((resolve) => {
+    const server = http.createServer((req, res) => {
+      if (req.method !== "POST" || req.url !== "/mcp") {
+        res.statusCode = 404;
+        res.end();
+        return;
+      }
+      const chunks: Buffer[] = [];
+      req.on("data", (c) => chunks.push(c));
+      req.on("end", () => {
+        const body = JSON.parse(Buffer.concat(chunks).toString("utf8"));
+        requests.push({ body });
+        if (body.method !== "tools/call") {
+          res.setHeader("content-type", "application/json");
+          res.end(JSON.stringify({ jsonrpc: "2.0", id: body.id, result: {} }));
+          return;
+        }
+        res.writeHead(200, { "content-type": "text/event-stream" });
+        opts.onCall(body, res);
+      });
+    });
+    server.listen(0, "127.0.0.1", () => {
+      const { port } = server.address() as AddressInfo;
+      resolve({
+        url: `http://127.0.0.1:${port}`,
+        requests,
+        close: () => new Promise((r) => server.close(() => r())),
+      });
+    });
+  });
+}
+
 /** Drive an in-process gateway Server via the SDK's request handlers. */
 async function callGateway(
   agents: EnabledAgent[],
   token: string | null,
   method: "tools/list" | "tools/call",
   params: any,
+  opts: {
+    gateway?: Partial<Omit<GatewayOptions, "agents" | "token" | "server">>;
+    extra?: any;
+  } = {},
 ) {
   const mcpServer = new Server(
     { name: "test", version: "0.0.0" },
     { capabilities: { tools: { listChanged: false } } },
   );
-  await buildGateway({ agents, token, server: mcpServer });
+  await buildGateway({ agents, token, server: mcpServer, ...opts.gateway });
   // Reach into the server's registered handlers — the SDK exposes them via
   // a private map, so we route through the public schema-keyed lookup we
   // know is wired up.
   const schema = method === "tools/list" ? ListToolsRequestSchema : CallToolRequestSchema;
   const handler = (mcpServer as any)._requestHandlers.get(schema.shape.method.value);
   if (!handler) throw new Error("handler not registered");
-  return handler({ method, params }, {} as any);
+  return handler({ method, params }, opts.extra ?? ({} as any));
 }
 
 test("tools/list aggregates upstream tools with agent prefix", async () => {
@@ -209,3 +249,74 @@ test("tools/call surfaces upstream JSON-RPC error as soft error", async () => {
     await upstream.close();
   }
 });
+
+test("tools/call forwards upstream SSE progress notifications", async () => {
+  const upstream = await startSseAgent({
+    onCall: (body, res) => {
+      res.write(
+        `data: ${JSON.stringify({
+          jsonrpc: "2.0",
+          method: "notifications/progress",
+          params: { progressToken: "p1", message: "halfway" },
+        })}\n\n`,
+      );
+      res.end(
+        `data: ${JSON.stringify({
+          jsonrpc: "2.0",
+          id: body.id,
+          result: {
+            content: [{ type: "text", text: "done" }],
+            isError: false,
+          },
+        })}\n\n`,
+      );
+    },
+  });
+  const notifications: any[] = [];
+  try {
+    const result = await callGateway(
+      [{ name: "streamer", url: upstream.url, addedAt: "now" }],
+      null,
+      "tools/call",
+      { name: `streamer${SEP}build`, arguments: {} },
+      {
+        extra: {
+          requestId: "req-1",
+          sendNotification: async (notification: any) => {
+            notifications.push(notification);
+          },
+        },
+      },
+    );
+    assert.equal(result.isError, false);
+    assert.deepEqual(notifications, [
+      {
+        method: "notifications/progress",
+        params: { progressToken: "p1", message: "halfway" },
+      },
+    ]);
+  } finally {
+    await upstream.close();
+  }
+});
+
+test("tools/call reports upstream SSE idle timeout", async () => {
+  const upstream = await startSseAgent({
+    onCall: (_body, res) => {
+      res.write(": connected\n\n");
+    },
+  });
+  try {
+    const result = await callGateway(
+      [{ name: "slow", url: upstream.url, addedAt: "now" }],
+      null,
+      "tools/call",
+      { name: `slow${SEP}build`, arguments: {} },
+      { gateway: { upstreamStreamIdleTimeoutMs: 25 } },
+    );
+    assert.equal(result.isError, true);
+    assert.match(result.content[0].text, /stream idle timeout/);
+  } finally {
+    await upstream.close();
+  }
+});