From 6130cb70a3d39581d237438fc1ef6a9de952b29b Mon Sep 17 00:00:00 2001
From: Divy Srivastava <dj.srivastava23@gmail.com>
Date: Mon, 4 Jul 2022 07:41:52 +0530
Subject: [PATCH] perf(ext/http): lazy load headers (#15055)

---
 ext/fetch/23_request.js | 37 +++++++++++++++++++++++++++++++------
 ext/http/01_http.js     |  4 ++--
 ext/http/lib.rs         | 21 +++++++++++++++++----
 3 files changed, 50 insertions(+), 12 deletions(-)

diff --git a/ext/fetch/23_request.js b/ext/fetch/23_request.js
index b61f46c61d..3058db6f71 100644
--- a/ext/fetch/23_request.js
+++ b/ext/fetch/23_request.js
@@ -43,6 +43,8 @@
 
   const _request = Symbol("request");
   const _headers = Symbol("headers");
+  const _getHeaders = Symbol("get headers");
+  const _headersCache = Symbol("headers cache");
   const _signal = Symbol("signal");
   const _mimeType = Symbol("mime type");
   const _body = Symbol("body");
@@ -52,7 +54,7 @@
    * @property {string} method
    * @property {() => string} url
    * @property {() => string} currentUrl
-   * @property {[string, string][]} headerList
+   * @property {() => [string, string][]} headerList
    * @property {null | typeof __window.bootstrap.fetchBody.InnerBody} body
    * @property {"follow" | "error" | "manual"} redirectMode
    * @property {number} redirectCount
@@ -64,7 +66,7 @@
   /**
    * @param {string} method
    * @param {string} url
-   * @param {[string, string][]} headerList
+   * @param {() => [string, string][]} headerList
    * @param {typeof __window.bootstrap.fetchBody.InnerBody} body
    * @param {boolean} maybeBlob
    * @returns
@@ -76,7 +78,16 @@
     }
     return {
       method,
-      headerList,
+      headerListInner: null,
+      get headerList() {
+        if (this.headerListInner === null) {
+          this.headerListInner = headerList();
+        }
+        return this.headerListInner;
+      },
+      set headerList(value) {
+        this.headerListInner = value;
+      },
       body,
       redirectMode: "follow",
       redirectCount: 0,
@@ -167,7 +178,21 @@
     /** @type {InnerRequest} */
     [_request];
     /** @type {Headers} */
-    [_headers];
+    [_headersCache];
+    [_getHeaders];
+
+    /** @type {Headers} */
+    get [_headers]() {
+      if (this[_headersCache] === undefined) {
+        this[_headersCache] = this[_getHeaders]();
+      }
+      return this[_headersCache];
+    }
+
+    set [_headers](value) {
+      this[_headersCache] = value;
+    }
+
     /** @type {AbortSignal} */
     [_signal];
     get [_mimeType]() {
@@ -210,7 +235,7 @@
       // 5.
       if (typeof input === "string") {
         const parsedURL = new URL(input, baseURL);
-        request = newInnerRequest("GET", parsedURL.href, [], null, true);
+        request = newInnerRequest("GET", parsedURL.href, () => [], null, true);
       } else { // 6.
         if (!ObjectPrototypeIsPrototypeOf(RequestPrototype, input)) {
           throw new TypeError("Unreachable");
@@ -451,7 +476,7 @@
     const request = webidl.createBranded(Request);
     request[_request] = inner;
     request[_signal] = signal;
-    request[_headers] = headersFromHeaderList(inner.headerList, guard);
+    request[_getHeaders] = () => headersFromHeaderList(inner.headerList, guard);
     return request;
   }
 
diff --git a/ext/http/01_http.js b/ext/http/01_http.js
index de546285d3..877342428e 100644
--- a/ext/http/01_http.js
+++ b/ext/http/01_http.js
@@ -111,7 +111,7 @@
         return null;
       }
 
-      const [streamRid, method, headersList, url] = nextRequest;
+      const [streamRid, method, url] = nextRequest;
       SetPrototypeAdd(this.managedResources, streamRid);
 
       /** @type {ReadableStream<Uint8Array> | undefined} */
@@ -126,7 +126,7 @@
       const innerRequest = newInnerRequest(
         method,
         url,
-        headersList,
+        () => core.opSync("op_http_headers", streamRid),
         body !== null ? new InnerBody(body) : null,
         false,
       );
diff --git a/ext/http/lib.rs b/ext/http/lib.rs
index 918e48120c..ce41a7ef2f 100644
--- a/ext/http/lib.rs
+++ b/ext/http/lib.rs
@@ -79,6 +79,7 @@ pub fn init() -> Extension {
       op_http_accept::decl(),
       op_http_read::decl(),
       op_http_write_headers::decl(),
+      op_http_headers::decl(),
       op_http_write::decl(),
       op_http_write_resource::decl(),
       op_http_shutdown::decl(),
@@ -365,8 +366,6 @@ struct NextRequestResponse(
   // This is a String rather than a ByteString because reqwest will only return
   // the method as a str which is guaranteed to be ASCII-only.
   String,
-  // headers:
-  Vec<(ByteString, ByteString)>,
   // url:
   String,
 );
@@ -403,12 +402,11 @@ async fn op_http_accept(
   });
 
   let method = request.method().to_string();
-  let headers = req_headers(request);
   let url = req_url(request, conn.scheme(), conn.addr());
 
   let stream_rid = state.borrow_mut().resource_table.add_rc(stream);
 
-  let r = NextRequestResponse(stream_rid, method, headers, url);
+  let r = NextRequestResponse(stream_rid, method, url);
   Ok(Some(r))
 }
 
@@ -561,6 +559,21 @@ async fn op_http_write_headers(
   }
 }
 
+#[op]
+fn op_http_headers(
+  state: &mut OpState,
+  rid: u32,
+) -> Result<Vec<(ByteString, ByteString)>, AnyError> {
+  let stream = state.resource_table.get::<HttpStreamResource>(rid)?;
+  let rd = RcRef::map(&stream, |r| &r.rd)
+    .try_borrow()
+    .ok_or_else(|| http_error("already in use"))?;
+  match &*rd {
+    HttpRequestReader::Headers(request) => Ok(req_headers(request)),
+    _ => unreachable!(),
+  }
+}
+
 fn http_response(
   data: Option<StringOrBuffer>,
   compressing: bool,