Sync bootstrap code

Author: mlafeldt

src/bootstrap/feature_flags.ts

@@ -9,6 +9,8 @@ export enum FeatureFlag {
   ForwardCDNLoop = "edge_functions_bootstrap_forward_cdn_loop",
   InvocationTimeout = "edge_functions_bootstrap_invocation_timeout",
   ForceHTTP11 = "edge_functions_bootstrap_force_http11",
+  UseOneClientPoolPerIsolate =
+    "edge_functions_bootstrap_use_one_client_pool_per_isolate",
 }
 
 export const hasFlag = (req: EdgeRequest, flag: FeatureFlag) => {

src/bootstrap/handler.ts

@@ -20,7 +20,10 @@ import { Router } from "./router.ts";
 import type { Functions } from "./stage_2.ts";
 import { ErrorType, PassthroughError, UserError } from "./util/errors.ts";
 import "./globals/types.ts";
-import { patchFetchToForceHTTP11 } from "./util/fetch.ts";
+import {
+  patchFetchToForceHTTP11,
+  patchFetchToHaveItsOwnConnectionPoolPerIsolate,
+} from "./util/fetch.ts";
 
 interface HandleRequestOptions {
   fetchRewrites?: Map<string, string>;
@@ -68,6 +71,17 @@ export const handleRequest = async (
     req.headers.get(InternalHeaders.FeatureFlags),
   );
 
+  // If the `UseOneClientPoolPerIsolate` feature flag is enabled, we patch the
+  // fetch to use its own connection pool.
+  if (featureFlags[FeatureFlag.UseOneClientPoolPerIsolate]) {
+    // this is not incuded in the `patchGlobals` function because that function
+    // is invoked before we have access to the feature flags. once this is fully
+    // rolled out, we will want to move this into `patchGlobals`
+    globalThis.fetch = patchFetchToHaveItsOwnConnectionPoolPerIsolate(
+      globalThis.fetch,
+    );
+  }
+
   // if ForceHTTP11 is enabled, we patch the fetch to enforce HTTP/1.1
   if (featureFlags[FeatureFlag.ForceHTTP11]) {
     // this is not incuded in the `patchGlobals` function because that function

src/bootstrap/util/fetch.ts

@@ -163,3 +163,24 @@ export const patchFetchToForceHTTP11 = (
     return rawFetch(input, { ...init, client });
   };
 };
+
+// We currently see issues with some requests on Deno and the current thinking is
+// something in the H2 client is broken and the client is entering a weird state
+// and either cannot get or lose a connection from the pool. This means that sometimes
+// a fetch doesn't reach us at all, it can't establish connection.
+// To mitigate this, we patch the fetch to use its own connection pool
+// so that it doesn't used the wider shared pool within Deno.
+let client: Deno.HttpClient;
+export let isClientPatched = false;
+export const patchFetchToHaveItsOwnConnectionPoolPerIsolate = (
+  rawFetch: typeof globalThis.fetch,
+) => {
+  if (isClientPatched) {
+    return rawFetch;
+  }
+  isClientPatched = true;
+  client = Deno.createHttpClient({});
+  return (input: URL | Request | string, init?: RequestInit) => {
+    return rawFetch(input, { ...init, client });
+  };
+};