AWS Lambda 函數全局變量 (AWS Lambda function global variables)

問題描述

AWS Lambda 函數全局變量 (AWS Lambda function global variables)

我正在用 JavaScript (Node.js) 編寫一個 AWS Lambda 函數，該函數通過 AWS 開發工具包與 CodeCommit 交互。

服務之間的通信按預期工作，我正在 CodeCommit 函數中獲取數據，但是當我想在函數之外使用這些數據時，就會出現我面臨的問題。

我嘗試了兩種方法：

1。全局變量

代碼：

var aws = require('aws‑sdk');
var codecommit = new aws.CodeCommit({ apiVersion: '2015‑04‑13' });
var repoName = ''; // Declared my global variable here

exports.handler = function(event, context) {

    var commitId = "69a5f8eeba340d71ba41b8f20d77cc20b301ff52"
    var repository = "my‑repository"

    var params = {
        repositoryName: repository
    };
    codecommit.getRepository(params, function(err, data) {
        if (err) {
            console.log(err);
            var message = "Error getting repository metadata for repository " + repository;
            console.log(message);
            context.fail(message);
        } else {
            console.log('Repository Name:', data.repositoryMetadata.repositoryName); // Shown with data
            repoName = data.repositoryMetadata.repositoryName; // Setting the variable
            console.log('Account Id:', data.repositoryMetadata.accountId); // Shown with data
        }
    });

    console.log(repoName); // Shown as blank in the output
};

輸出：
最後寫入的“console.log” 是第一個打印在執行結果中，但顯示為空白。然後打印另外兩個console.log（在函數內），並顯示數據。

2。函數

代碼：

var aws = require('aws‑sdk');
var codecommit = new aws.CodeCommit({ apiVersion: '2015‑04‑13' });

exports.handler = function(event, context) {

    var commitId = "69a5f8eeba340d71ba41b8f20d77cc20b301ff52"
    var repository = "my‑repository"

    var repoData = getRepository(repository)

    console.log('Repository Name:', repoData.repositoryName);
    console.log('Account Id:', repoData.accountId);
};

function getRepository(repository) {
    var params = {
        repositoryName: repository
    };
    codecommit.getRepository(params, function(err, data) {
        if (err) {
            console.log(err);
            var message = "Error getting repository metadata for repository " + repository;
            console.log(message);
            context.fail(message);
        } else {
            var repoData = {};
            repoData.repositoryName = data.repositoryMetadata.repositoryName;
            repoData.accountId = data.repositoryMetadata.accountId;
            console.log(repoData); // Shows output in execution results when lines 11 & 12 are commented
            return repoData;
        }
    });
}

輸出：

{
  "errorType": "TypeError",
  "errorMessage": "Cannot read property 'repositoryName' of undefined",
  "trace": [
    "TypeError: Cannot read property 'repositoryName' of undefined",
    "    at Runtime.exports.handler (/var/task/index.js:57:46)",
    "    at Runtime.handleOnce (/var/runtime/Runtime.js:66:25)"
  ]
}

結論
這些方法都不起作用。數據始終在函數內可見，但從不在函數外。我懷疑函數外部的代碼在函數本身之前執行，我想知道我是否可以讓代碼在執行 console.log 之前等待函數已經執行（以及之後的其他操作）。或者也許我在另一個層面上錯了？

參考解法

方法 1:

You are using a callback model, in which case the console.log in the first example is being hit before the code in the callback. A better option would be to use async/await.

var aws = require('aws‑sdk');

var codecommit = new aws.CodeCommit({ apiVersion: '2015‑04‑13' });

var repoName = ''; // Declared my global variable here

exports.handler = async function(event, context) {
var commitId = "69a5f8eeba340d71ba41b8f20d77cc20b301ff52"
var repository = "my‑repository"

var params = {
    repositoryName: repository
};
var data = await codecommit.getRepository(params).promise();

console.log('Repository Name:', data.repositoryMetadata.repositoryName); // Shown with data
repoName = data.repositoryMetadata.repositoryName; // Setting the variable
console.log('Account Id:', data.repositoryMetadata.accountId); // Shown with data

console.log(repoName);

};

</code></pre>
Notice that I'm not catching the error here, but if you wanted to you can use a try/catch block. Just be sure you throw a new error in that case if you want the function to fail.
(by GuillaumeExia、Jason Wadsworth)
參考文件


AWS Lambda function global variables (CC BY‑SA 2.5/3.0/4.0)