在AWS Lambda中将字符串附加到文本文件Nodejs

Question

场景：文本文件快照ID。txt位于S3存储桶中。我正在尝试创建一个每天运行的Lambda函数（Cron），该函数将使用AWS CLI拍摄卷的快照，然后将该快照ID保存到S3中的文本文件中。下次创建另一个快照时，新的快照ID将保存到S3中的同一个文本文件中。文本文件是快照ID的占位符，当它达到阈值时，它将删除顶部快照ID，并在末尾添加新快照ID（FIFO管道）。

对于不使用AWS lambda的人，我的问题是，向变量追加文本并返回包含新行的新变量的最快方式是什么。

对于了解Lambda的人来说，这是AWS Lambda的基本代码，我使用fs。appendFile，但是如何使用从s3.getObject（）获得的文件并最终将其传递给s3.putObject（）？

编辑：这是我的进步：

console.log('Loading function');

var aws = require('aws-sdk');
var s3 = new aws.S3({ apiVersion: '2006-03-01' });
var fs = require('fs');

exports.handler = function(event, context) {
    //console.log('Received event:', JSON.stringify(event, null, 2));

    // Get the object from the event and show its content type
    var bucket = event.Records[0].s3.bucket.name;
    var key = decodeURIComponent(event.Records[0].s3.object.key.replace(/\+/g, ' '));
    var params = {
        Bucket: bucket,
        Key: key
    };
    s3.getObject(params, function(err, data) {
        if (err) {
            console.log(err);
            var message = "Error getting object " + key + " from bucket " + bucket +
                ". Make sure they exist and your bucket is in the same region as this function.";
            console.log(message);
            context.fail(message);
        } else {
            // fs.appendFile('snapshot-ids.txt', 'snap-001', function (err) {
            //     if (err) throw err;
            //     console.log('The "data to append" was appended to file!');
            // });
            console.log(params_new);
            console.log('CONTENT TYPE getObject:', data.ContentType);
            // context.succeed(data.Body.toString('ascii'));
        }
    });
    var params_new = {
        Bucket: bucket,
        Key: key,
        Body: 'snap-002'
    };
    s3.putObject(params_new, function(err, data) {
                console.log('put here');
                if (err) {
                    console.log(err);
                    var message = "Error getting object " + key + " from bucket " + bucket +
                        ". Make sure they exist and your bucket is in the same region as this function.";
                    console.log(message);
                    context.fail(message);
                } else {
                    console.log('CONTENT TYPE putObject:', data.ContentType);
                    context.succeed(data.ContentType);
                }
    });
};

Answer 1

到目前为止，我注意到了您的代码中的一些事情。。。

>

在s3.getObject完成并且您拥有s3中的文件之前，您不能调用s3.putObject。

您没有处理文件系统，因为您从s3.getObject获取数据。

考虑到这些事情，我修改了您的代码（我还没有尝试过，但它应该会让您朝着正确的方向前进）：

console.log('Loading function');

var aws = require('aws-sdk');
var s3 = new aws.S3({ apiVersion: '2006-03-01' });

exports.handler = function(event, context) {
    //console.log('Received event:', JSON.stringify(event, null, 2));

    // Get the object from the event and show its content type
    var bucket = event.Records[0].s3.bucket.name;
    var key = decodeURIComponent(event.Records[0].s3.object.key.replace(/\+/g, ' '));
    var params = {
        Bucket: bucket,
        Key: key
    };
    s3.getObject(params, function(err, data) {
        if (err) {
            console.log(err);
            var message = "Error getting object " + key + " from bucket " + bucket +
                ". Make sure they exist and your bucket is in the same region as this function.";
            console.log(message);
            context.fail(message);
        } else {
            console.log(params_new);
            console.log('CONTENT TYPE getObject:', data.ContentType);

            // convert body(file contents) to a string so we can append
            var body = data.Body.toString('utf-8');
            // append data
            body += 'snap-001\n';

            var params_new = {
                Bucket: bucket,
                Key: key,
                Body: body
            };
            //NOTE this call is now nested in the s3.getObject call so it doesn't happen until the response comes back
            s3.putObject(params_new, function(err, data) {
                        console.log('put here');
                        if (err) {
                            console.log(err);
                            var message = "Error getting object " + key + " from bucket " + bucket +
                                ". Make sure they exist and your bucket is in the same region as this function.";
                            console.log(message);
                            context.fail(message);
                        } else {
                            console.log('CONTENT TYPE putObject:', data.ContentType);
                            context.succeed(data.ContentType);
                        }
            });

        }
    });

};

另一个需要记住的是，如果你有超过一个这个Lambda同时运行，它们很可能会相互践踏。听起来你只需要每天安排一次，所以这没什么大不了的，但值得一提。