完善serverless部署环境

server/db.js

@@ -1,37 +1,70 @@
 const mysql = require('mysql2/promise');
 
 let pool;
+const IS_SERVERLESS = [
+  process.env.SERVERLESS,
+  process.env.VERCEL,
+  process.env.AWS_LAMBDA_FUNCTION_NAME,
+  process.env.NETLIFY,
+  process.env.FUNCTION_TARGET,
+  process.env.K_SERVICE
+].some(Boolean);
 
-function initPool() {
-  if (pool) {
-    pool.end().catch(e => console.error('Error closing pool:', e));
+function getConnectionLimit() {
+  const parsed = parseInt(process.env.MYSQL_CONNECTION_LIMIT, 10);
+  if (!Number.isNaN(parsed) && parsed > 0) {
+    return parsed;
   }
-  pool = mysql.createPool({
+  return IS_SERVERLESS ? 2 : 10;
+}
+
+function createPool() {
+  return mysql.createPool({
     host: process.env.MYSQL_HOST || 'localhost',
-    port: parseInt(process.env.MYSQL_PORT) || 3306,
+    port: parseInt(process.env.MYSQL_PORT, 10) || 3306,
     user: process.env.MYSQL_USER || 'root',
     password: process.env.MYSQL_PASSWORD || '',
     database: process.env.MYSQL_DATABASE || 'display_wall',
     waitForConnections: true,
-    connectionLimit: 10,
-    queueLimit: 0
+    connectionLimit: getConnectionLimit(),
+    queueLimit: 0,
+    enableKeepAlive: true,
+    keepAliveInitialDelay: 0
   });
 }
 
+function getPool() {
+  if (!pool) {
+    pool = createPool();
+  }
+  return pool;
+}
+
+function initPool({ force = false } = {}) {
+  if (pool && !force) {
+    return pool;
+  }
+
+  if (pool) {
+    pool.end().catch(e => console.error('Error closing pool:', e));
+  }
+
+  pool = createPool();
+  return pool;
+}
+
 async function checkHealth() {
   try {
-    if (!pool) return { status: 'down', error: 'Database pool not initialized' };
-    await pool.query('SELECT 1');
+    await getPool().query('SELECT 1');
     return { status: 'up' };
   } catch (err) {
     return { status: 'down', error: err.message };
   }
 }
 
-initPool();
-
 module.exports = {
-  query: (...args) => pool.query(...args),
+  query: (...args) => getPool().query(...args),
+  getPool,
   initPool,
   checkHealth
 };