feat: 集成阿里云日志服务(SLS)

- 添加 aliyun-log SDK 依赖
- 新增 sls-logger.js 模块，支持批量日志上报、静默降级
- 在四个 API 处理函数中集成请求日志记录
- 更新 .env.example 添加 SLS 配置示例

sls-logger.js

@@ -0,0 +1,149 @@
+/**
+ * 阿里云日志服务（SLS）日志模块
+ * 
+ * 功能：
+ * - 将 API 请求/响应日志上报到阿里云 SLS
+ * - 批量上报，减少 API 调用
+ * - 环境变量缺失时静默降级
+ */
+
+import aliyunLog from 'aliyun-log';
+const { Client, PutLogsRequest, LogItem, LogContent } = aliyunLog;
+
+// SLS 配置
+const SLS_CONFIG = {
+    accessKeyId: process.env.ALIYUN_ACCESS_KEY_ID,
+    accessKeySecret: process.env.ALIYUN_ACCESS_KEY_SECRET,
+    endpoint: process.env.ALIYUN_SLS_ENDPOINT,
+    project: process.env.ALIYUN_SLS_PROJECT,
+    logstore: process.env.ALIYUN_SLS_LOGSTORE
+};
+
+// 检查配置是否完整
+const isConfigured = Object.values(SLS_CONFIG).every(v => v);
+
+let client = null;
+let logQueue = [];
+const BATCH_SIZE = 10;
+const FLUSH_INTERVAL_MS = 5000;
+
+// 初始化 SLS Client
+function initClient() {
+    if (!isConfigured) {
+        console.warn('[SLS] 阿里云日志服务未配置，日志将仅输出到控制台');
+        return null;
+    }
+
+    try {
+        client = new Client({
+            accessKeyId: SLS_CONFIG.accessKeyId,
+            accessKeySecret: SLS_CONFIG.accessKeySecret,
+            endpoint: SLS_CONFIG.endpoint
+        });
+        console.log('[SLS] 阿里云日志服务客户端初始化成功');
+        return client;
+    } catch (error) {
+        console.error('[SLS] 初始化失败:', error.message);
+        return null;
+    }
+}
+
+// 刷新日志队列
+async function flushLogs() {
+    if (!client || logQueue.length === 0) return;
+
+    const logsToSend = logQueue.splice(0, BATCH_SIZE);
+
+    try {
+        const logItems = logsToSend.map(log => {
+            const contents = Object.entries(log).map(([key, value]) => {
+                return new LogContent({
+                    key,
+                    value: String(value ?? '')
+                });
+            });
+            return new LogItem({
+                time: Math.floor(Date.now() / 1000),
+                contents
+            });
+        });
+
+        const request = new PutLogsRequest({
+            projectName: SLS_CONFIG.project,
+            logStoreName: SLS_CONFIG.logstore,
+            logGroup: {
+                logs: logItems
+            }
+        });
+
+        await client.putLogs(request);
+        console.log(`[SLS] 成功上报 ${logsToSend.length} 条日志`);
+    } catch (error) {
+        console.error('[SLS] 日志上报失败:', error.message);
+        // 失败的日志重新入队（可选：限制重试次数）
+        logQueue.unshift(...logsToSend);
+    }
+}
+
+// 定时刷新
+let flushTimer = null;
+function startFlushTimer() {
+    if (flushTimer || !isConfigured) return;
+    flushTimer = setInterval(flushLogs, FLUSH_INTERVAL_MS);
+}
+
+/**
+ * 记录 API 请求日志
+ * @param {Object} logData - 日志数据
+ * @param {string} logData.method - HTTP 方法
+ * @param {string} logData.endpoint - 请求路径
+ * @param {string} logData.model - 模型 ID
+ * @param {number} logData.status - 响应状态码
+ * @param {number} logData.duration_ms - 请求耗时
+ * @param {number} [logData.input_tokens] - 输入 Token 数
+ * @param {number} [logData.output_tokens] - 输出 Token 数
+ * @param {string} [logData.error] - 错误信息
+ */
+export function logRequest(logData) {
+    const enrichedLog = {
+        timestamp: new Date().toISOString(),
+        ...logData
+    };
+
+    // 始终输出到控制台
+    console.log('[SLS]', JSON.stringify(enrichedLog));
+
+    if (!isConfigured) return;
+
+    logQueue.push(enrichedLog);
+
+    // 队列满时立即刷新
+    if (logQueue.length >= BATCH_SIZE) {
+        flushLogs();
+    }
+}
+
+/**
+ * 优雅关闭，刷新剩余日志
+ */
+export async function shutdown() {
+    if (flushTimer) {
+        clearInterval(flushTimer);
+        flushTimer = null;
+    }
+    await flushLogs();
+    console.log('[SLS] 已关闭');
+}
+
+// 初始化
+initClient();
+startFlushTimer();
+
+// 进程退出时优雅关闭
+process.on('SIGTERM', shutdown);
+process.on('SIGINT', shutdown);
+
+export default {
+    logRequest,
+    shutdown
+};