当xstate调用promise时，AWS lambda实例关闭

Question

我有一个lambda函数，它使用xstate按顺序执行某些任务，其中一个步骤是将数据保存到dynamo db。但我的lambda在执行下面这行代码后立即结束执行。

const response = await new DynamoDB.DocumentClient().put(params).promise();

我的代码：

import {Handler} from "aws-lambda";
import {interpret} from 'xstate';
import { Machine} from "xstate";
import {PutItemInput} from "aws-sdk/clients/dynamodb";
import {DynamoDB} from "aws-sdk";

export const recordProcessor: Handler = async (event) => {
  console.log('records size----->', event.Records.length);
  for (const record of event.Records) {
      const body = JSON.parse(record.body);
      console.log('body ----->', body);

    interpret(Machine({id:'test',
      context:body,
      initial: 'start',
      states:{
        start: {
          invoke: {
            src: context => initiate(context),
            onDone: {
              target: 'success'
            }
          }
        },
        success: {
          type: 'final'
        }
      }
    })).onTransition(state => {
      if (state.changed) {
        console.log('state ----> ', state.value);
      }
    }).onDone(() => console.log('done--->')).start();
  }


  async function initiate(context: any) {
    console.log('DbDynamoImpl ::: insert ::: start :::');
    let params: PutItemInput = {
      TableName: 'test',
      Item: context
    };
    try {
      const response = await new DynamoDB.DocumentClient().put(params).promise();
      console.log('DbDynamoImpl ::: insert ::: response :::', response);
      return true;
    } catch (e) {
      console.log("DynamoDb insert error", e);
      return false;
    }
  }

};

Answer 1

您正在解析Promise，然后再执行return语句。你能尝试用你需要返回的值来resolve Promise吗？然后，它将使用这些值转到onDone块。此外，这里有try和catch块是多余的，因为xstate中的service会自动为您处理这些问题。

只需返回服务调用语句中的promise，因为它需要是一个返回Promise的函数

​

function initiate(context: any) {
  console.log('DbDynamoImpl ::: insert ::: start :::');
  let params: PutItemInput = {
    TableName: 'test',
    Item: context,
  };
  return new DynamoDB.DocumentClient().put(params).promise();
}

​

然后在您的onDone块中，您可以console.log('DbDynamoImpl ::: insert ::: response :::', response);

​

onDone: {
  target: 'success',
  actions: (ctx, e) => console.log('DbDynamoImpl ::: insert ::: response :::', e),
}

​

Answer 2

通过将机器解释和交互封装到promise中，您可以等待状态机进入最终状态。

大致类似于以下内容

export const recordProcessor: Handler = async (event) => {
  console.log('records size----->', event.Records.length);
  for (const record of event.Records) {
      const body = JSON.parse(record.body);
      console.log('body ----->', body);
      await setupMachine(...);
...
}

function setupMachine(...){
  return new Promise((resolve, reject) => {
    interpret(Machine({id:'test',
      context:body,
      initial: 'start',
      states:{
        start: {
          invoke: {
            src: context => initiate(context),
            onDone: {
              target: 'success'
            }
          }
        },
        success: {
          type: 'final'
        }
      }
    })).onTransition(state => {
      if (state.changed) {
        console.log('state ----> ', state.value);
      }
    })
     .onDone(() => { console.log('done--->'); return resolve()})
     .onStop(() => reject());
     .start();
   }
  });
}

Answer 3

将async添加到函数中，然后再次测试它。

exports.handler = async (event, context) => {
    return ...
}