更新备注：的确使用了 promise.all + reduce 方法取出的全量数据，但是目前库里只有3条数据，还是会偶发性的报 -501004；

18:11 分 集中报了一波错，大概 14 条：

{
  "message": "errCode: -501004 exceed concurrent request limit | errMsg: [LimitExceeded.NoValidConnection] Connection num overrun. Please improve specifications, but if the problem cannot be solved, contact us.; ",
  "name": "",
  "stack": "Error: errCode: -501004 exceed concurrent request limit | errMsg: [LimitExceeded.NoValidConnection] Connection num overrun. Please improve specifications, but if the problem cannot be solved, contact us.; \n    at Object.returnAsCloudSDKError (/var/user/node_modules/wx-server-sdk/index.js:6052:16)\n    at Object.checkError (/var/user/node_modules/wx-server-sdk/index.js:1378:23)\n    at Promise (/var/user/node_modules/wx-server-sdk/index.js:1508:33)\n    at \n    at process._tickCallback (internal/process/next_tick.js:188:7)",
  "userInfo": {
    "appId": "wx4bfbc8e64eff19eb"
  }
}

然后登陆云函数后台查看日志发现，下面提示

日志内容 Request ID: 4c830adf-14b7-4fff-b2cd-3487add8034f
执行时间: 9372.41ms内存使用: 37.93 MB
返回结果 null

日志
START RequestId: 4c830adf-14b7-4fff-b2cd-3487add8034f

Event RequestId: 4c830adf-14b7-4fff-b2cd-3487add8034f

2020-01-16T10:11:53.154Z  Database operation database.queryDocument is longer than 3s. Please check query performance and your network environment.

 
END RequestId: 4c830adf-14b7-4fff-b2cd-3487add8034f

Report RequestId: 4c830adf-14b7-4fff-b2cd-3487add8034f Duration:9372ms Memory:256MB MaxMemoryUsed:37.929688MB

大概从 17: 57 开始，执行时间由 70ms 升到 3、4 秒，中间甚至十几秒，到 18: 11 分后定时任务停止。