versioned lambdas in s3

lambda.js

import * as https from 'https';
import { NodeHttpHandler } from '@aws-sdk/node-http-handler';
import { promises as fs } from 'fs';
import path from 'path';
import { S3Client, GetObjectCommand, ListObjectsV2Command } from '@aws-sdk/client-s3';

// Create an HTTPS agent with keep-alive enabled
const keepAliveAgent = new https.Agent({
  keepAlive: true,
  maxSockets: 50, // Maximum number of sockets to allow per host
  maxFreeSockets: 10, // Maximum number of sockets to leave open in a free state
  timeout: 60000, // Socket idle timeout
  freeSocketTimeout: 30000 // Free socket keep-alive for 30 seconds
});

// Initialize the S3 client for the us-east-1 region
const s3 = new S3Client({
  region: <--s3-region-->,
  requestHandler: new NodeHttpHandler({
    httpsAgent: keepAliveAgent
  })
});
const BUCKET_NAME = <--Bucket-->;

// Helper function to download a file from S3
async function downloadFileFromS3(bucket, key, localPath) {
  // Skip if key is a directory
  if (!key.endsWith('/')) {
    const command = new GetObjectCommand({ Bucket: bucket, Key: key });
    const data = await s3.send(command);

    // Ensure the directory structure is present
    await fs.mkdir(path.dirname(localPath), { recursive: true });

    // Write the data to a local file
    await fs.writeFile(localPath, data.Body);
  }
}

// Helper function to list files under a specific S3 prefix
async function listFiles(bucket, prefix) {
  const command = new ListObjectsV2Command({ Bucket: bucket, Prefix: prefix });
  const data = await s3.send(command);
  return data.Contents.map(content => content.Key);
}

// Helper function to download all files for a specific version prefix
async function downloadVersionedFiles(bucket, versionPrefix) {
  const files = await listFiles(bucket, versionPrefix);
  for (const fileKey of files) {
    if (!fileKey.endsWith('/')) { // Skip directories
      const localPath = path.join('/tmp', fileKey);
      await downloadFileFromS3(bucket, fileKey, localPath);
    }
  }
}

// Lambda handler function
export const handler = async (event) => {
  const rawPath = event.rawPath;
  const pathParts = rawPath.split('/').filter(Boolean); // Splits and removes empty strings

  // Validate the path structure
  if (pathParts.length < 4) {
    return { statusCode: 400, body: 'Invalid path. Expected format: /org/repo/version/filename.js' };
  }

  // Extract path components
  const [org, repo, version, ...rest] = pathParts;
  const filename = rest.join('/');
  const versionPrefix = `${org}/${repo}/${version}/`;

  try {
    // Download files from the specified versioned S3 path
    await downloadVersionedFiles(BUCKET_NAME, versionPrefix);

    const filePath = path.join('/tmp', versionPrefix, filename);
    // Check if the file exists and is not a directory
    try {
      await fs.access(filePath);
    } catch {
      return { statusCode: 404, body: 'File not found.' };
    }

    // Dynamically import the module from the local file
    // make sure to have package.json in the directory with { type: "module" }
    const module = await import(filePath);

    // Execute the module's default export if it exists
    if (module.default) {
      const result = await module.default(event);
      return { statusCode: 200, body: JSON.stringify(result) };
    } else {
      return { statusCode: 500, body: 'No default export found in module.' };
    }
  } catch (error) {
    console.error('Error:', error);
    return { statusCode: 500, body: JSON.stringify({ message: 'Execution failed', error: error.message }) };
  }
};