From 25fdcfbd1499d123798e32d7b32e70c74b6ffc05 Mon Sep 17 00:00:00 2001
From: Yulong Wang <7679871+fs-eire@users.noreply.github.com>
Date: Mon, 7 Mar 2022 11:35:06 -0800
Subject: [PATCH] [js/web] allow multiple inference session creating
 concurrently (#10784)

* test case

* bugfix

* fix

* support multi session init
---
 js/common/lib/backend-impl.ts                   | 17 ++++++++++-------
 .../browser-test-wasm-multi-session-create.js   | 10 ++++++++++
 js/web/test/e2e/common.js                       |  6 +++++-
 js/web/test/e2e/run.js                          |  1 +
 4 files changed, 26 insertions(+), 8 deletions(-)
 create mode 100644 js/web/test/e2e/browser-test-wasm-multi-session-create.js

diff --git a/js/common/lib/backend-impl.ts b/js/common/lib/backend-impl.ts
index 518c573238..91c92247d2 100644
--- a/js/common/lib/backend-impl.ts
+++ b/js/common/lib/backend-impl.ts
@@ -7,7 +7,7 @@ interface BackendInfo {
   backend: Backend;
   priority: number;
 
-  initializing?: boolean;
+  initPromise?: Promise<void>;
   initialized?: boolean;
   aborted?: boolean;
 }
@@ -67,22 +67,25 @@ export const resolveBackend = async(backendHints: readonly string[]): Promise<Ba
     if (backendInfo) {
       if (backendInfo.initialized) {
         return backendInfo.backend;
-      } else if (backendInfo.initializing) {
-        throw new Error(`backend "${backendName}" is being initialized; cannot initialize multiple times.`);
       } else if (backendInfo.aborted) {
         continue;  // current backend is unavailable; try next
       }
 
+      const isInitializing = !!backendInfo.initPromise;
       try {
-        backendInfo.initializing = true;
-        await backendInfo.backend.init();
+        if (!isInitializing) {
+          backendInfo.initPromise = backendInfo.backend.init();
+        }
+        await backendInfo.initPromise;
         backendInfo.initialized = true;
         return backendInfo.backend;
       } catch (e) {
-        errors.push({name: backendName, err: e});
+        if (!isInitializing) {
+          errors.push({name: backendName, err: e});
+        }
         backendInfo.aborted = true;
       } finally {
-        backendInfo.initializing = false;
+        delete backendInfo.initPromise;
       }
     }
   }
diff --git a/js/web/test/e2e/browser-test-wasm-multi-session-create.js b/js/web/test/e2e/browser-test-wasm-multi-session-create.js
new file mode 100644
index 0000000000..1ac7a99b52
--- /dev/null
+++ b/js/web/test/e2e/browser-test-wasm-multi-session-create.js
@@ -0,0 +1,10 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License.
+
+'use strict';
+
+it('Browser E2E testing - WebAssembly backend (multiple inference session create calls)', async function () {
+  const sessionPromiseA = createSession(ort);
+  const sessionPromiseB = createSession(ort);
+  await Promise.all([sessionPromiseA, sessionPromiseB]);
+});
diff --git a/js/web/test/e2e/common.js b/js/web/test/e2e/common.js
index 4c0db6dc1a..7f478a5095 100644
--- a/js/web/test/e2e/common.js
+++ b/js/web/test/e2e/common.js
@@ -7,8 +7,12 @@ function assert(cond) {
   if (!cond) throw new Error();
 }
 
+var createSession = function(ort, options) {
+  return ort.InferenceSession.create('./model.onnx', options || {});
+}
+
 var testFunction = async function (ort, options) {
-  const session = await ort.InferenceSession.create('./model.onnx', options || {});
+  const session = await createSession(ort, options);
 
   const dataA = Float32Array.from([1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12]);
   const dataB = Float32Array.from([10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120]);
diff --git a/js/web/test/e2e/run.js b/js/web/test/e2e/run.js
index 9a681ccd19..517ff7b849 100644
--- a/js/web/test/e2e/run.js
+++ b/js/web/test/e2e/run.js
@@ -100,6 +100,7 @@ async function testAllBrowserCases({ hostInKarma }) {
   await runKarma({ hostInKarma, main: './browser-test-webgl.js', ortMain: 'ort.webgl.min.js'});
   await runKarma({ hostInKarma, main: './browser-test-wasm.js'});
   await runKarma({ hostInKarma, main: './browser-test-wasm.js', ortMain: 'ort.wasm.min.js'});
+  await runKarma({ hostInKarma, main: './browser-test-wasm-multi-session-create.js'});
   await runKarma({ hostInKarma, main: './browser-test-wasm-no-threads.js'});
   await runKarma({ hostInKarma, main: './browser-test-wasm-no-threads.js', ortMain: 'ort.wasm-core.min.js'});
   await runKarma({ hostInKarma, main: './browser-test-wasm-proxy.js'});