node.js - 我的 Lambda 在代码完成之前结束 - node.js

Question

我知道以前有人以各种方式问过这个问题，但我无法弄清楚。我对 Node.js 和 lambda 还很陌生。如果我运行 lambda 两次，此代码将起作用，但第一次永远不会运行完成。如果我通过添加从本地 IDE 运行它，这也可以正常工作exports.handler();到代码块的末尾。

该代码查询 DynamoDB 的结果，然后尝试从 Dynamo 中删除这些记录。查询部分似乎每次都有效，但删除部分在第一次调用时未能发生。我似乎无法弄清楚 lambda 需要进行哪些更改才能等到我的所有流程完成。

提前致谢。

// Load the AWS SDK for Node.js
var AWS = require('aws-sdk');
// Set the region
AWS.config.update({ region: 'us-east-2' });
exports.handler = async (event) => {
    // Create DynamoDB service object
    const ddb = new AWS.DynamoDB({ apiVersion: '2012-08-10' });
    const documentClient = new AWS.DynamoDB.DocumentClient({ region: "us-east-2" });
    const tablename = process.env.table_name;

    let dynapromises = [];

    let params = {
        ExpressionAttributeValues: {
            ':offNum': { S: process.env.cost_center },
            ':s': { N: '2' }
        },
        ExpressionAttributeNames: {
            "#notif_status": "status"
        },
        KeyConditionExpression: 'officeNumber = :offNum',
        TableName: tablename,
        IndexName: 'officeNumberIndex',
        ProjectionExpression: "notificationNumber",
        FilterExpression: '(attribute_not_exists(#notif_status) or #notif_status = :s) and attribute_not_exists(statusTimes)'
    };

    let qresults = await ddb.query(params).promise();
    console.log("Count of notifs again " + qresults.Items.length);

    qresults.Items.forEach(function(element, index, array) {
        console.log(element.notificationNumber.S);
        let delparams = {
            TableName: tablename,
            ReturnValues: "ALL_OLD",
            Key: {
                notificationNumber: {
                    S: element.notificationNumber.S
                }
            }
        };

        dynapromises.push(ddb.deleteItem(delparams).promise().then(function(data) {
            console.log("Deleted Record:"+ JSON.stringify(data)); // successful response
        }, function(error) {
            console.log(error, error.stack); // an error occurred
        }));
        console.log("deletion parameters " + JSON.stringify(delparams));
    });
    Promise.all(dynapromises).then(res => {
        console.log("All promises done");
    });
    return qresults.Items.length;
};

Answer 1

问题在于您在所有 promise 完成之前返回，您需要将 return qresults.Items.length; 移到最后一个 then 内。

尝试使用此代码:

** 更新:使用工作代码更改代码片段 **

// Load the AWS SDK for Node.js
const AWS = require('aws-sdk');
// Set the region
AWS.config.update({ region: 'us-east-2' });
exports.handler = async (event) => {
    // Create DynamoDB service object
    const ddb = new AWS.DynamoDB({ apiVersion: '2012-08-10' });
    const documentClient = new AWS.DynamoDB.DocumentClient({ region: "us-east-2" });
    const tablename = process.env.table_name;

    let params = {
        ExpressionAttributeValues: {
            ':offNum': { S: process.env.cost_center },
            ':s': { N: '2' }
        },
        ExpressionAttributeNames: {
            "#notif_status": "status"
        },
        KeyConditionExpression: 'officeNumber = :offNum',
        TableName: tablename,
        IndexName: 'officeNumberIndex',
        ProjectionExpression: "notificationNumber",
        FilterExpression: '(attribute_not_exists(#notif_status) or #notif_status = :s) and attribute_not_exists(statusTimes)'
    };

    let qresults = await ddb.query(params).promise();
    console.log("Count of notifs again " + qresults.Items.length);

    const dynapromises = qresults.Items.map( async element => {
    	let delparams = {
            TableName: tablename,
            ReturnValues: "ALL_OLD",
            Key: {
                notificationNumber: {
                    S: element.notificationNumber.S
                }
            }
        };

        try {
        	 console.log("deletion parameters " + JSON.stringify(delparams));
	        const data = await ddb.deleteItem(delparams).promise();
    	    console.log( "Deleted Record:"+ JSON.stringify(data) );
        } catch ( err ) {
        	console.log(error, error.stack); // an error occurred
        }
    } )

    await Promise.all(dynapromises)

    console.log("All promises done");
    return qresults.Items.length;
};