gatsby in aws lambda

index.js

const AWS = require("aws-sdk");
const {link} = require("linkfs");
const mock = require('mock-require');
const fs = require('fs');
const tmpDir = require('os').tmpdir();

exports.handler = (event, context) => {
  rewriteFs();
  invokeGatsby(context);
}

const invokeGatsby = (context) => {
  const gatsby = require("gatsby/dist/commands/build");

  gatsby({
        directory: __dirname,
  })
  .then(uploadFilesToS3)
  .then(invalidateCloudFront)
  .then(context.succeed)
  .catch(context.fail);
};

//TODO replace with in-memory-fs ?!
const rewriteFs = () => {
  // redirect paths
  const linkedFs = link(fs, [
    [`${__dirname}/.cache`, tmpDir+"/.cache"],
    [`${__dirname}/public`, tmpDir+"/public"]
  ]);
  
  // those are missing in linkfs
  linkedFs.ReadStream = fs.ReadStream;
  linkedFs.WriteStream = fs.WriteStream;
  
  // replace fs with linkfs globally
  mock('fs', linkedFs);
}