修正分頁、Too many connection 問題

lib/database-middleware.ts

@@ -0,0 +1,156 @@
+// =====================================================
+// 資料庫連線管理中間件
+// =====================================================
+
+import { NextRequest, NextResponse } from 'next/server';
+import { db } from './database';
+import { dbMonitor } from './database-monitor';
+
+// 連線池狀態追蹤
+let connectionCount = 0;
+const maxConnections = 3; // 與資料庫配置保持一致
+
+export function withDatabaseConnection<T extends any[]>(
+  handler: (...args: T) => Promise<NextResponse>
+) {
+  return async (...args: T): Promise<NextResponse> => {
+    // 檢查連線池狀態
+    if (connectionCount >= maxConnections) {
+      console.warn(`⚠️ 連線池已滿 (${connectionCount}/${maxConnections})，等待可用連線...`);
+      
+      // 等待一段時間後重試
+      await new Promise(resolve => setTimeout(resolve, 100));
+      
+      if (connectionCount >= maxConnections) {
+        return NextResponse.json(
+          { 
+            success: false, 
+            error: '資料庫連線池已滿，請稍後再試',
+            retryAfter: 5 // 建議5秒後重試
+          },
+          { status: 503 }
+        );
+      }
+    }
+
+    connectionCount++;
+    
+    try {
+      const result = await handler(...args);
+      return result;
+    } catch (error) {
+      console.error('資料庫操作錯誤:', error);
+      
+      // 根據錯誤類型返回適當的響應
+      if (error instanceof Error) {
+        if (error.message.includes('ER_CON_COUNT_ERROR')) {
+          return NextResponse.json(
+            { 
+              success: false, 
+              error: '資料庫連線數已達上限，請稍後再試',
+              retryAfter: 10
+            },
+            { status: 503 }
+          );
+        } else if (error.message.includes('ECONNRESET') || error.message.includes('PROTOCOL_CONNECTION_LOST')) {
+          return NextResponse.json(
+            { 
+              success: false, 
+              error: '資料庫連線中斷，請重試',
+              retryAfter: 3
+            },
+            { status: 503 }
+          );
+        }
+      }
+      
+      return NextResponse.json(
+        { 
+          success: false, 
+          error: '資料庫操作失敗',
+          details: error instanceof Error ? error.message : '未知錯誤'
+        },
+        { status: 500 }
+      );
+    } finally {
+      connectionCount--;
+    }
+  };
+}
+
+// 連線池健康檢查
+export async function checkConnectionHealth(): Promise<{
+  isHealthy: boolean;
+  connectionCount: number;
+  maxConnections: number;
+  usagePercentage: number;
+}> {
+  try {
+    const stats = dbMonitor.getConnectionStats();
+    
+    return {
+      isHealthy: stats.usagePercentage < 80,
+      connectionCount: stats.currentConnections,
+      maxConnections: stats.maxConnections,
+      usagePercentage: stats.usagePercentage
+    };
+  } catch (error) {
+    console.error('連線健康檢查失敗:', error);
+    return {
+      isHealthy: false,
+      connectionCount: 0,
+      maxConnections: 0,
+      usagePercentage: 100
+    };
+  }
+}
+
+// 自動釋放空閒連線
+export async function autoReleaseIdleConnections(): Promise<boolean> {
+  try {
+    const health = await checkConnectionHealth();
+    
+    if (health.usagePercentage > 70) {
+      console.log('🔄 連線使用率過高，嘗試釋放空閒連線...');
+      return await dbMonitor.releaseIdleConnections();
+    }
+    
+    return true;
+  } catch (error) {
+    console.error('自動釋放連線失敗:', error);
+    return false;
+  }
+}
+
+// 連線池監控
+export function startConnectionMonitoring() {
+  // 每30秒檢查一次連線狀態
+  dbMonitor.startMonitoring(30000);
+  
+  // 每5分鐘嘗試釋放空閒連線
+  setInterval(async () => {
+    await autoReleaseIdleConnections();
+  }, 5 * 60 * 1000);
+  
+  console.log('🔍 資料庫連線監控已啟動');
+}
+
+// 優雅的關閉
+export async function gracefulShutdown() {
+  console.log('🔄 正在優雅關閉資料庫連線...');
+  
+  try {
+    dbMonitor.stopMonitoring();
+    await db.close();
+    console.log('✅ 資料庫連線已關閉');
+  } catch (error) {
+    console.error('❌ 關閉資料庫連線時發生錯誤:', error);
+  }
+}
+
+// 處理程序退出事件
+if (typeof process !== 'undefined') {
+  process.on('SIGINT', gracefulShutdown);
+  process.on('SIGTERM', gracefulShutdown);
+  process.on('exit', gracefulShutdown);
+}