node.js - 如何解决：在 Node.js 服务器的 onclosenexttick 处过早关闭？

Question

如何解决此错误，我正在使用 AWS IoT 运行我的 Node.js，然后它有时会显示此错误：

      throw er; // Unhandled 'error' event
      ^

Error: How  (/home/ec2-user/work/nodejs_27_01/node_modules/end-of-stream/index.js:54:                                                                                                     86)
    at processTicksAndRejections (internal/process/task_queues.js:79:11)
Emitted 'error' event on DeviceClient instance at:
    at MqttClient.<anonymous> (/home/ec2-user/work/nodejs_27_01/node_modules/aws-iot-device-sdk/                                                                                                     device/index.js:772:15)
    at MqttClient.emit (events.js:333:22)
    at MqttClient.EventEmitter.emit (domain.js:485:12)
    at TLSSocket.f (/home/ec2-user/work/nodejs_27_01/node_modules/once/once.js:25:25)
    at onclosenexttick (/home/ec2-user/work/nodejs_27_01/node_modules/end-of-stream/index.js:54:                                                                                                     73)

标签： node.jsamazon-web-servicesaws-iot

Answer 1

这可能有多种原因：

具有相同 ClientId 的多个连接

clientId 一次只能用于一个连接。如果在建立另一个连接时使用相同的 clientId 进行连接，则旧连接将被丢弃（这会导致过早关闭错误）并建立新连接。

客户端正在使用已在使用的客户端 ID。在这种情况下，已经连接的客户端将被断开 [...]。（来源）

权限

如果设备（来自aws-iot-device-sdk-js 的 mqtt.Client）没有正确的权限来连接和/或发布/订阅/接收给定主题的消息，则可能会发生此错误。

有关更多文档，请参见此处：https ://docs.aws.amazon.com/iot/latest/developerguide/pub-sub-policy.html

该策略应如下所示（示例显示Cloudformation 物联网策略资源）：

MyIotThingsPolicy:
  Type: AWS::IoT::Policy
  Properties:
    PolicyDocument:
      Version: "2012-10-17"
      Statement:
        - Action: iot:Connect
          Effect: Allow
          Resource: !Join [ "", [!Sub "arn:aws:iot:${AWS::Region}:${AWS::AccountId}:client/",
                                 "${iot:ClientId}"] ]
        - Action: iot:Receive
          Effect: Allow
          Resource: !Join [ "", [!Sub "arn:aws:iot:${AWS::Region}:${AWS::AccountId}:topic/",
                                "${iot:ClientId}/eg/your/broadcast/topic"] ]
        - Action: iot:Subscribe
          Effect: Allow
          Resource: !Join [ "", [!Sub "arn:aws:iot:${AWS::Region}:${AWS::AccountId}:topicfilter/",
                                 "${iot:ClientId}/eg/your/broadcast/topic"] ]
        - Action: iot:Publish
          Effect: Allow
          Resource: !Join [ "", [!Sub "arn:aws:iot:${AWS::Region}:${AWS::AccountId}:topic/",
                                 "${iot:ClientId}/eg/your/publish/topic"] ]

这!Join是必要的，因为 Cloudformation 会尝试解析${iot:ClientId}，这是一个运行时值，在部署期间是未知的。

故障排除

• 正如Sandeep Patel还建议的那样，如果你想在客户端对这种情况采取行动，你应该实现一个错误回调：

  device.on('error', (error) => {
    // error.message might be 'premature close'
  });
  

• You can also look for disconnectReason on the topic $aws/events/presence/disconnected/<clientId>, see: https://docs.aws.amazon.com/iot/latest/developerguide/life-cycle-events.html