3 files changed, 54 insertions, 2 deletions

diff --git a/cli/tests/unit/serve_test.ts b/cli/tests/unit/serve_test.ts
index 0f97e17b8..c26d3f751 100644
--- a/cli/tests/unit/serve_test.ts
+++ b/cli/tests/unit/serve_test.ts
@@ -10,6 +10,7 @@ import {
   assertThrows,
   Deferred,
   deferred,
+  execCode,
   fail,
 } from "./test_util.ts";
 
@@ -56,6 +57,21 @@ Deno.test(async function httpServerShutsDownPortBeforeResolving() {
   listener!.close();
 });
 
+Deno.test(
+  { permissions: { read: true, run: true } },
+  async function httpServerUnref() {
+    const [statusCode, _output] = await execCode(`
+      async function main() {
+        const server = Deno.serve({ port: 4501, handler: () => null });
+        server.unref();
+        await server.finished; // This doesn't block the program from exiting
+      }
+      main();
+    `);
+    assertEquals(statusCode, 0);
+  },
+);
+
 Deno.test(async function httpServerCanResolveHostnames() {
   const ac = new AbortController();
   const listeningPromise = deferred();
diff --git a/cli/tsc/dts/lib.deno.unstable.d.ts b/cli/tsc/dts/lib.deno.unstable.d.ts
index c0c0d16ad..70d7ef7c4 100644
--- a/cli/tsc/dts/lib.deno.unstable.d.ts
+++ b/cli/tsc/dts/lib.deno.unstable.d.ts
@@ -1312,7 +1312,19 @@ declare namespace Deno {
      * the signal passed to {@linkcode ServeOptions.signal}.
      */
     finished: Promise<void>;
+
+    /**
+     * Make the server block the event loop from finishing.
+     *
+     * Note: the server blocks the event loop from finishing by default.
+     * This method is only meaningful after `.unref()` is called.
+     */
+    ref(): void;
+
+    /** Make the server not block the event loop from finishing. */
+    unref(): void;
   }
+
   /** **UNSTABLE**: New API, yet to be vetted.
    *
    * Serves HTTP requests with the given handler.
diff --git a/ext/http/00_serve.js b/ext/http/00_serve.js
index 7186da1fe..2fb36d044 100644
--- a/ext/http/00_serve.js
+++ b/ext/http/00_serve.js
@@ -43,6 +43,7 @@ const {
   SetPrototypeAdd,
   SetPrototypeDelete,
   Symbol,
+  SymbolFor,
   TypeError,
   Uint8Array,
   Uint8ArrayPrototype,
@@ -660,13 +661,22 @@ function serve(arg1, arg2) {
 
   onListen({ port: listenOpts.port });
 
+  let ref = true;
+  let currentPromise = null;
+  const promiseIdSymbol = SymbolFor("Deno.core.internalPromiseId");
+
   // Run the server
   const finished = (async () => {
     while (true) {
       const rid = context.serverRid;
       let req;
       try {
-        req = await op_http_wait(rid);
+        currentPromise = op_http_wait(rid);
+        if (!ref) {
+          core.unrefOp(currentPromise[promiseIdSymbol]);
+        }
+        req = await currentPromise;
+        currentPromise = null;
       } catch (error) {
         if (ObjectPrototypeIsPrototypeOf(BadResourcePrototype, error)) {
           break;
@@ -691,7 +701,21 @@ function serve(arg1, arg2) {
     }
   })();
 
-  return { finished };
+  return {
+    finished,
+    ref() {
+      ref = true;
+      if (currentPromise) {
+        core.refOp(currentPromise[promiseIdSymbol]);
+      }
+    },
+    unref() {
+      ref = false;
+      if (currentPromise) {
+        core.unrefOp(currentPromise[promiseIdSymbol]);
+      }
+    },
+  };
 }
 
 internals.addTrailers = addTrailers;