Unblock server on multiple HTTP requests (denoland/deno_std#3)

Original: https://github.com/denoland/deno_std/commit/1bf555ab2f9c6074b07697d72cb93f276ecf5bb1

2 files changed, 80 insertions, 31 deletions

diff --git a/http.ts b/http.ts
index c7d2851c0..2dab9e1e5 100644
--- a/http.ts
+++ b/http.ts
@@ -4,37 +4,82 @@ import { TextProtoReader } from "./textproto.ts";
 import { STATUS_TEXT } from "./http_status";
 import { assert } from "./util";
 
-export async function* serve(addr: string) {
-  const listener = listen("tcp", addr);
-  while (true) {
-    const c = await listener.accept();
-    yield* serveConn(c);
+interface Deferred {
+  promise: Promise<{}>;
+  resolve: () => void;
+  reject: () => void;
+}
+
+function deferred(): Deferred {
+  let resolve, reject;
+  const promise = new Promise((res, rej) => {
+    resolve = res;
+    reject = rej;
+  });
+  return {
+    promise,
+    resolve,
+    reject
+  };
+}
+
+interface ServeEnv {
+  reqQueue: ServerRequest[];
+  serveDeferred: Deferred;
+}
+
+// Continuously read more requests from conn until EOF
+// Mutually calling with maybeHandleReq
+// TODO: make them async function after this change is done
+// https://github.com/tc39/ecma262/pull/1250
+// See https://v8.dev/blog/fast-async
+export function serveConn(env: ServeEnv, conn: Conn) {
+  readRequest(conn).then(maybeHandleReq.bind(null, env, conn));
+}
+function maybeHandleReq(env: ServeEnv, conn: Conn, maybeReq: any) {
+  const [req, _err] = maybeReq;
+  if (_err) {
+    conn.close(); // assume EOF for now...
+    return;
   }
-  listener.close();
+  env.reqQueue.push(req); // push req to queue
+  env.serveDeferred.resolve(); // signal while loop to process it
+  // TODO: protection against client req flooding
+  serveConn(env, conn); // try read more (reusing connection)
 }
 
-export async function* serveConn(c: Conn) {
-  let bufr = new BufReader(c);
-  let bufw = new BufWriter(c);
-  try {
-    while (true) {
-      const [req, err] = await readRequest(bufr);
-      if (err == "EOF") {
-        break;
-      }
-      if (err == "ShortWrite") {
-        console.log("ShortWrite error");
-        break;
-      }
-      if (err) {
-        throw err;
-      }
-      req.w = bufw;
-      yield req;
+export async function* serve(addr: string) {
+  const listener = listen("tcp", addr);
+  const env: ServeEnv = {
+    reqQueue: [], // in case multiple promises are ready
+    serveDeferred: deferred()
+  };
+
+  // Routine that keeps calling accept
+  const acceptRoutine = () => {
+    const handleConn = (conn: Conn) => {
+      serveConn(env, conn); // don't block
+      scheduleAccept(); // schedule next accept
+    };
+    const scheduleAccept = () => {
+      listener.accept().then(handleConn);
+    };
+    scheduleAccept();
+  };
+
+  acceptRoutine();
+
+  // Loop hack to allow yield (yield won't work in callbacks)
+  while (true) {
+    await env.serveDeferred.promise;
+    env.serveDeferred = deferred(); // use a new deferred
+    let queueToProcess = env.reqQueue;
+    env.reqQueue = [];
+    for (const result of queueToProcess) {
+      yield result;
     }
-  } finally {
-    c.close();
   }
+  listener.close();
 }
 
 interface Response {
@@ -75,7 +120,7 @@ class ServerRequest {
     setContentLength(r);
 
     if (r.headers) {
-      for (let [key, value] of r.headers) {
+      for (const [key, value] of r.headers) {
         out += `${key}: ${value}\r\n`;
       }
     }
@@ -93,9 +138,12 @@ class ServerRequest {
   }
 }
 
-async function readRequest(b: BufReader): Promise<[ServerRequest, BufState]> {
-  const tp = new TextProtoReader(b);
+async function readRequest(c: Conn): Promise<[ServerRequest, BufState]> {
+  const bufr = new BufReader(c);
+  const bufw = new BufWriter(c);
   const req = new ServerRequest();
+  req.w = bufw;
+  const tp = new TextProtoReader(bufr);
 
   let s: string;
   let err: BufState;
@@ -109,5 +157,7 @@ async function readRequest(b: BufReader): Promise<[ServerRequest, BufState]> {
 
   [req.headers, err] = await tp.readMIMEHeader();
 
+  // TODO: handle body
+
   return [req, err];
 }
diff --git a/http_test.ts b/http_test.ts
index e6cb87f01..b0007a892 100644
--- a/http_test.ts
+++ b/http_test.ts
@@ -5,8 +5,7 @@ const addr = "0.0.0.0:8000";
 const s = serve(addr);
 console.log(`listening on http://${addr}/`);
 
-const body = (new TextEncoder()).encode("Hello World\n");
-
+const body = new TextEncoder().encode("Hello World\n");
 
 async function main() {
   for await (const req of s) {