如何在AWS Lambda中用Node.js向现有Zip文件夹添加JSON文件？

Great question! Unfortunately, easy-zip is a bit outdated and doesn’t support modifying existing zip files reliably. But there are two solid Node.js modules you can use instead: adm-zip (simple, good for most cases) and yauzl + yazl (low-level, ideal for large zips that can’t fit in memory). Let’s break down how to use both, including how to implement this in AWS Lambda.

Using adm-zip (Simplest Approach) #

Adm-zip is a popular, easy-to-use module that supports reading existing zips and adding new files directly to them.

Step 1: Install the module #

npm install adm-zip

Step 2: Basic Local Usage Code #

This example loads your existing zip, adds a JSON file, and saves the modified zip back to disk:

const AdmZip = require('adm-zip');
const fs = require('fs');

// Configure paths and filenames
const existingZipPath = './downloaded-from-s3.zip';
const jsonFilePath = './your-data.json';
const internalZipFileName = 'metadata.json'; // Name the file will have inside the zip

// Load the existing zip
const zip = new AdmZip(existingZipPath);

// Read the JSON file content
const jsonContent = fs.readFileSync(jsonFilePath, 'utf8');

// Add the JSON content to the zip
zip.addFile(internalZipFileName, Buffer.from(jsonContent, 'utf8'));

// Save the modified zip
zip.writeZip('./updated-zip.zip');

console.log('JSON file added to zip successfully!');

For AWS Lambda Environment #

Lambda restricts writing to the /tmp directory only (which offers up to 10GB of space in newer runtimes). You’ll need to download the zip from S3 to /tmp, modify it, then upload the updated zip back to S3.

Step 1: Dependencies #

adm-zip needs to be included in your deployment package, while aws-sdk is pre-installed in Lambda environments.

Step 2: Lambda Function Code #

const AdmZip = require('adm-zip');
const AWS = require('aws-sdk');
const s3 = new AWS.S3();
const fs = require('fs');
const path = require('path');

exports.handler = async (event) => {
    // Configuration - adjust these values to match your setup
    const s3Bucket = 'your-s3-bucket-name';
    const originalZipKey = 'path/to/existing-zip.zip';
    const modifiedZipKey = 'path/to/updated-zip.zip';
    const jsonContent = JSON.stringify({ user: 'Vishnu', timestamp: new Date().toISOString() }); // Your JSON data
    const internalZipFileName = 'added-data.json';

    try {
        // 1. Download the original zip from S3 to /tmp
        const zipResponse = await s3.getObject({ Bucket: s3Bucket, Key: originalZipKey }).promise();
        const tempZipPath = path.join('/tmp', 'existing.zip');
        fs.writeFileSync(tempZipPath, zipResponse.Body);

        // 2. Load the zip and add the JSON file
        const zip = new AdmZip(tempZipPath);
        zip.addFile(internalZipFileName, Buffer.from(jsonContent, 'utf8'));

        // 3. Save the modified zip to /tmp
        const modifiedTempPath = path.join('/tmp', 'updated.zip');
        zip.writeZip(modifiedTempPath);

        // 4. Upload the modified zip back to S3
        await s3.putObject({
            Bucket: s3Bucket,
            Key: modifiedZipKey,
            Body: fs.readFileSync(modifiedTempPath)
        }).promise();

        return {
            statusCode: 200,
            body: JSON.stringify('JSON file added to zip successfully!')
        };
    } catch (error) {
        console.error('Error processing zip:', error);
        return {
            statusCode: 500,
            body: JSON.stringify('Failed to modify zip file')
        };
    }
};

Lambda-specific Notes: #

• Permissions: Ensure your Lambda execution role has s3:GetObject for the original zip and s3:PutObject for the modified zip.
• Large Zips: If your zip is multiple gigabytes, adm-zip may cause out-of-memory errors since it loads the entire zip into memory. For these cases, use the yauzl + yazl approach below.
• Ephemeral Storage: /tmp is cleared after Lambda invocations, so don’t rely on it for persistent storage.

Alternative: yauzl + yazl (For Large Zips) #

This approach streams zip content instead of loading everything into memory, making it ideal for large files.

Step 1: Install Modules #

npm install yauzl yazl

Step 2: Streaming Code (Local Example) #

const yauzl = require('yauzl');
const yazl = require('yazl');
const fs = require('fs');

// Open the existing zip for streaming
yauzl.open('./existing.zip', { lazyEntries: true }, (err, zipIn) => {
    if (err) throw err;
    
    // Create a new zip file to write to
    const zipOut = new yazl.ZipFile();
    const outputStream = fs.createWriteStream('./modified.zip');
    zipOut.outputStream.pipe(outputStream);

    // Copy all existing entries from the original zip to the new one
    zipIn.readEntry();
    zipIn.on('entry', (entry) => {
        zipIn.openReadStream(entry, (err, readStream) => {
            if (err) throw err;
            zipOut.addReadStream(readStream, entry.fileName);
            zipIn.readEntry();
        });
    });

    // Add the JSON file once all existing entries are copied
    zipIn.on('end', () => {
        zipOut.addBuffer(
            Buffer.from(JSON.stringify({ data: 'large-zip-compatible' }), 'utf8'),
            'new-json-file.json'
        );
        zipOut.end();
    });
});

In Lambda, you can adapt this to stream directly to S3 instead of writing to /tmp (using s3.upload with streams) for even better memory efficiency.

内容的提问来源于stack exchange，提问作者Vishnu Ranganathan