Question

我一直在尝试（并且失败）使用Node version 8.10中的s3.getObject从S3存储桶加载文件。

我找到了一篇很棒的帖子，上面的答复几乎有效here，但是该语法在8.10中不太起作用，而且无论我如何重新排列代码，我都无法使其正常工作。

var AWS = require('aws-sdk')
var s3 = new AWS.S3();

var fileData = null;

exports.handler = (event, context, callback) => {
    console.log('I am in the main procedure');
    var params = {
        Bucket: "change_for_your_bucket",
        Key:  "change_to_your_json_file"
    };

    fetchDataFromS3(params);
    console.log('I am in the main procedure, the function above should be waiting but it is not');
    waitForFileLoadBeforeDoingSomething(event, context, callback);

    const s = JSON.stringify(fileData.Body.toString('utf-8'));
    console.log(`this is the file: ${s}`);
    console.log('I have the file!(dg.2)');    

};

function fetchDataFromS3(params)
{
    console.log('-------------- fetchDataFromS3:Start -------------------------');
    // gets the object from s3 => promise
    const uploadPromise = s3.getObject(params).promise();

    // returns the body of the s3 object
    uploadPromise
            .then(function(data) {
                console.log("successfully downloaded data");
                fileData = data.Body.toString();

            })
            .catch(function download(err) {console.log(err,err.stack); throw err;});


    console.log('-------------- fetchDataFromS3:Done -------------------------');
}



function waitForFileLoadBeforeDoingSomething(event, context, callback){
    if(!fileData){
        console.log('No file available to me as yet, lets sleep for a bit');
        setTimeout(function(){
            waitForFileLoadBeforeDoingSomething(event, context, callback);
        }, 300);
    } 
}

输出如下。

Function Logs:
START RequestId: cb16f155-c0d7-11e8-ad01-f5991c5adaaf Version: $LATEST
2018-09-25T15:29:29.759Z    cb16f155-c0d7-11e8-ad01-f5991c5adaaf    I am in the main procedure
2018-09-25T15:29:29.759Z    cb16f155-c0d7-11e8-ad01-f5991c5adaaf    -------------- fetchDataFromS3:Start -------------------------
2018-09-25T15:29:29.811Z    cb16f155-c0d7-11e8-ad01-f5991c5adaaf    -------------- fetchDataFromS3:Done -------------------------
2018-09-25T15:29:29.811Z    cb16f155-c0d7-11e8-ad01-f5991c5adaaf    I am in the main procedure, the function above should be waiting but it is not
2018-09-25T15:29:29.811Z    cb16f155-c0d7-11e8-ad01-f5991c5adaaf    No file available to me as yet, lets sleep for a bit
2018-09-25T15:29:29.812Z    cb16f155-c0d7-11e8-ad01-f5991c5adaaf    TypeError: Cannot read property 'Body' of null
    at exports.handler (/var/task/dg3.js:17:39)

您可以看到我没有点击“成功下载数据”行，并且如果我犯了一个错误并且该函数仍在异步运行，或者如果我已经有了promise的语法，我将无法解决。错误的。

Answer 1

首先，您必须更改入口点方法。就像您在尝试使用8.10节点运行时之前提到的那样，然后是以下代码部分：

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

您必须更改为：

export async function <function_name>(event) {}

ref：https://aws.amazon.com/blogs/compute/node-js-8-10-runtime-now-available-in-aws-lambda/

然后该函数的路径应为：

<module_name>.<function_name>

此外，您不需要以下代码部分：

function waitForFileLoadBeforeDoingSomething(event, context, callback){
    if(!fileData){
        console.log('No file available to me as yet, lets sleep for a bit');
        setTimeout(function(){
            waitForFileLoadBeforeDoingSomething(event, context, callback);
        }, 300);
    } 
}

然后摆脱var声明。不要搞乱范围。只需使用：

const AWS = require('aws-sdk');

下一步是创建一个S3实例：

const S3 = new AWS.S3({region: process.env.AWS_REGION, apiVersion: '2006-03-01'});
// with region of your AWS account and current API verstion;

为您的提取方法声明参数：

const params = 
{
  Bucket: 'STRING_VALUE', // a path to your Bucket
  Key: 'STRING_VALUE' // a key (literally a path to your file)
}

ref：https://docs.aws.amazon.com/AWSJavaScriptSDK/latest/AWS/S3.html#getObject-property

您不必对事件进行字符串化，因为它已经被字符串化了：

const s = JSON.stringify(fileData.Body.toString('utf-8'));

最后：

try
{
    const result = await S3.getObject(params).promise();
    // if successful then:
    console.log(`Check the result: ${result}`);
}
catch (ex) // if an error occured
{
     console.error(ex);
}

还请确保运行时5分钟（您可以调整后仅用于调试）并增加lambda的内存（也用于测试）。

使用Node.js版本8.10在Lambda中加载S3文件

1 个答案: