项目场景：

nodejs koa web服务
1、并发请求日志须包含traceId以便方便分析
2、请求周期内用户数据隔离

两种解决办法都可以

• AsyncLocalStorage
  用 AsyncLocalStorage 存储
• Context Request
  直接在request 中保存

const uuid = require('uuid');
const { AsyncLocalStorage } = require('async_hooks');
const als = new AsyncLocalStorage();

// 在中间件中
app.use(async(ctx, next) => {
	// 1 AsyncLocalStorage
	const traceId = ctx.request.header['x-trace-id'];
	als.enterWith(traceId ? traceId : uuid.v4());
	// 2 Context Request
	ctx.request._data = {id: uuid.v4()};
	// 引用
	console.log(`[trace:${als.getStore()}] ->`, ctx.request._data.id) // <----
	await next();
});

router.get('/', async(ctx, next) => {

  let res = null;
  res = await new Promise((resolve, reject) => {
    setTimeout(function() {
      console.log(`[trace:${als.getStore()}] /=>`, ctx.request._data.id); // <----
      resolve(true);
    }, 500);
  });

});