fix: [http] Consume unread body and trailers before reading next request (#3990)

- Added `ServerRequest.finalize()`:  consuming all unread body stream and trailers.
  - This is cleanup method for reading next request from same keep-alive connection.
  - Needed when handler didn't consume all body and trailers even after responding.
- refactor: `ServerRequest._bodyStream()`, `ServerRequestBody` are removed.
  - Now using `bodyReader()` and `chunkedBodyReader()` instead.
- fix: Trailers should only be read `transfer-encoding` is `chunked` and `trailer` header is set and its value is valid.
- fix: use `Headers.append()` on reading trailers.
- fix: delete `trailer` field from headers after reading trailers.
- reorg: Several functions related to IO are moved into `http/io.ts`

1 files changed, 29 insertions, 7 deletions

diff --git a/std/http/racing_server.ts b/std/http/racing_server.ts
index 629fef2db..0b0e5a8a5 100644
--- a/std/http/racing_server.ts
+++ b/std/http/racing_server.ts
@@ -5,12 +5,15 @@ import { delay } from "../util/async.ts";
 const addr = Deno.args[1] || "127.0.0.1:4501";
 const server = serve(addr);
 
-const body = new TextEncoder().encode("Hello 1\n");
-const body4 = new TextEncoder().encode("World 4\n");
-
-async function delayedRespond(request: ServerRequest): Promise<void> {
+function body(i: number): string {
+  return `Step${i}\n`;
+}
+async function delayedRespond(
+  request: ServerRequest,
+  step: number
+): Promise<void> {
   await delay(3000);
-  await request.respond({ status: 200, body });
+  await request.respond({ status: 200, body: body(step) });
 }
 
 async function largeRespond(request: ServerRequest, c: string): Promise<void> {
@@ -19,6 +22,13 @@ async function largeRespond(request: ServerRequest, c: string): Promise<void> {
   await request.respond({ status: 200, body: b });
 }
 
+async function ignoreToConsume(
+  request: ServerRequest,
+  step: number
+): Promise<void> {
+  await request.respond({ status: 200, body: body(step) });
+}
+
 console.log("Racing server listening...\n");
 
 let step = 1;
@@ -28,7 +38,7 @@ for await (const request of server) {
       // Try to wait long enough.
       // For pipelining, this should cause all the following response
       // to block.
-      delayedRespond(request);
+      delayedRespond(request, step);
       break;
     case 2:
       // HUGE body.
@@ -38,8 +48,20 @@ for await (const request of server) {
       // HUGE body.
       largeRespond(request, "b");
       break;
+    case 4:
+      // Ignore to consume body (content-length)
+      ignoreToConsume(request, step);
+      break;
+    case 5:
+      // Ignore to consume body (chunked)
+      ignoreToConsume(request, step);
+      break;
+    case 6:
+      // Ignore to consume body (chunked + trailers)
+      ignoreToConsume(request, step);
+      break;
     default:
-      request.respond({ status: 200, body: body4 });
+      request.respond({ status: 200, body: body(step) });
       break;
   }
   step++;