From e175a4d2ed02d69a7d4b1ab4ec1e51a81cef2141 Mon Sep 17 00:00:00 2001
From: heerim hong <devheerim@gmail.com>
Date: Sun, 10 Nov 2024 16:15:42 +0900
Subject: [PATCH] =?UTF-8?q?=EC=9E=90=EB=B0=94=EC=8A=A4=ED=81=AC=EB=A6=BD?=
 =?UTF-8?q?=ED=8A=B8=20:=20Mutex?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 .gitignore                                    |  3 +-
 .../concurrent/my-mutex.js"                   | 63 +++++++++++++++++++
 .../concurrent/recursive-async.js"            | 17 +++++
 3 files changed, 82 insertions(+), 1 deletion(-)
 create mode 100644 "\354\236\220\353\260\224\354\212\244\355\201\254\353\246\275\355\212\270/concurrent/my-mutex.js"
 create mode 100644 "\354\236\220\353\260\224\354\212\244\355\201\254\353\246\275\355\212\270/concurrent/recursive-async.js"

diff --git a/.gitignore b/.gitignore
index 54bae13..22eafaf 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1 +1,2 @@
-/**/tempCodeRunnerFile.js
\ No newline at end of file
+/**/tempCodeRunnerFile.js
+/**/node_modules
\ No newline at end of file
diff --git "a/\354\236\220\353\260\224\354\212\244\355\201\254\353\246\275\355\212\270/concurrent/my-mutex.js" "b/\354\236\220\353\260\224\354\212\244\355\201\254\353\246\275\355\212\270/concurrent/my-mutex.js"
new file mode 100644
index 0000000..7cc1508
--- /dev/null
+++ "b/\354\236\220\353\260\224\354\212\244\355\201\254\353\246\275\355\212\270/concurrent/my-mutex.js"
@@ -0,0 +1,63 @@
+/**
+ * Promise.all을 사용하는 경우, 한번에 모든 Promise를 처리하므로, mutex를 걸어준다.
+ * 혹은 forEach, map 대신 reduce를 사용하거나, for문 사용해도 가능하다.
+ */
+
+class Mutex {
+  constructor() {
+    this._isLocked = false;
+  }
+
+  lock() {
+    this._isLocked = true;
+  }
+
+  unlock() {
+    this._isLocked = false;
+  }
+
+  release() {
+    this.unlock();
+  }
+
+  async acquire(count = 0) {
+    if (count >= 10) throw new Error("Mutex lock count exceeded");
+
+    const isLocked = this._isLocked;
+    if (!isLocked) {
+      this.lock();
+      return Promise.resolve();
+    } else {
+      return new Promise((resolve) => {
+        setTimeout(() => {
+          this.acquire(count + 1).then(resolve);
+        }, 100);
+      });
+    }
+  }
+}
+
+let sum = 0;
+const mutex = new Mutex();
+
+const wait = () =>
+  new Promise((resolve) => setTimeout(resolve, Math.random() * 50));
+
+async function add(order) {
+  await mutex.acquire();
+  console.log(`[${order}] start`);
+
+  await wait(); // async logic
+  sum += 1;
+
+  console.log(`[${order}] end`);
+  mutex.release();
+}
+
+async function main() {
+  console.log("start");
+  await Promise.all([add(1), add(2), add(3)]);
+  console.log("end");
+}
+
+main();
diff --git "a/\354\236\220\353\260\224\354\212\244\355\201\254\353\246\275\355\212\270/concurrent/recursive-async.js" "b/\354\236\220\353\260\224\354\212\244\355\201\254\353\246\275\355\212\270/concurrent/recursive-async.js"
new file mode 100644
index 0000000..47f9a4c
--- /dev/null
+++ "b/\354\236\220\353\260\224\354\212\244\355\201\254\353\246\275\355\212\270/concurrent/recursive-async.js"
@@ -0,0 +1,17 @@
+async function recursiveAsync(count = 0) {
+  console.log("count is", count);
+  return new Promise((resolve) =>
+    setTimeout(async () => {
+      await recursiveAsync(count + 1);
+      resolve();
+    }, 500)
+  );
+}
+
+async function main() {
+  console.log("start");
+  await recursiveAsync();
+  console.log("end");
+}
+
+main();