How to run binary from a lambda properly? - node.js

Question

I'm trying to make sox audio binary run from the lambda, I followed this guide: http://marcelog.github.io/articles/static_sox_transcoding_lambda_mp3.html
So I created sox binary using docker with last Amazon Linux version and deployed lambda as zip package with structure:
sox
index.js
Lambda code:
exports.handler = async (event) => {
initializeContext();
try {
const object = await getFile("test.mp3");
const fs = require('fs');
fs.writeFileSync("/tmp/test.mp3", object.Body);
let result = child_process.execFileSync('sox', ['/tmp/test.mp3', '/tmp/testOutput.mp3', ... <filter params here>], {
encoding: 'ascii'
// shell: true
});
const file = fs.readFileSync("/tmp/testOutput.mp3");
await putFile("testOutput.mp3", file);
}
catch(err) {
try {
await log("error", err);
}
catch(err) {}
}
};
let getFile = async function(fileName) {
const params = {
Bucket: bucket,
Key: fileName
};
return await s3.getObject(params).promise();
};
let putFile = async function(fileName, body) {
const params = {
Bucket: bucket,
Key: fileName,
Body: body
};
await s3.putObject(params).promise();
};
So, I need to get file from S3, process it and return result. S3 loading is tested to work. However, I get "EACCES" error on trying to start "sox" process.
What could I miss? Can it originate from the fact that I used the last Amazon Linux image but Lambda use more old version?

Answer 1

I was struggling with the same for processing audio files. The npm package came handy.
https://github.com/stojanovic/lambda-audio
If your command is,
sox input.mp3 -c 1 output.wav
your node code will be like the following,
const lambdaAudio = require('lambda-audio')
lambdaAudio.sox('./input.mp3 -c 1 /tmp/output.wav')
.then(response => {
// Do something when the file was converted
})
.catch(errorResponse => {
console.log('Error from the sox command:', errorResponse)
})
and leave all the complex issues to the npm package.
Hope it helps.

Answer 2

Finally I've found that to ensure file permissions I have to create zip package inside Amazon Linux docker image. So you need to
npm i lambda-audio
there, then zip node_modules along with your index.js.
My lambda package zip root folder is:
node_modules // npm i lambda-audio result
index.js
Working solution for Node 8.10 Runtime with memory consumption optimizations:
process.env["PATH"] = process.env["PATH"] + ":" + process.env["LAMBDA_TASK_ROOT"];
const AWS = require("aws-sdk");
const s3 = new AWS.S3();
const lambdaAudio = require("lambda-audio");
let bucket;
exports.handler = async (event) => {
try {
bucket = event.bucket;
const { inputFileName, outputFileName } = event;
const fs = require("fs");
const inputStream = fs.createWriteStream("/tmp/input.mp3");
await getFileToStream(inputFileName, inputStream);
await lambdaAudio.sox("/tmp/input.mp3 /tmp/output.mp3 <YOUR FILTERS HERE>);
fs.unlinkSync("/tmp/input.mp3"); // removing unused input file
const outputStream = fs.createReadStream("/tmp/output.mp3");
await uploadFileFromStream(outputFileName, outputStream);
}
catch(err) {
// Logging
}
};
let getFileToStream = async function(fileName, writeStream) {
const params = {
Bucket: bucket,
Key: fileName
};
const readStream = s3.getObject(params).createReadStream();
const end = new Promise((resolve, reject) => {
writeStream.on('close', () => resolve());
writeStream.on('error', (err) => reject(err));
readStream.on('error', (err) => reject(err));
});
readStream.pipe(writeStream);
return end;
};
let uploadFileFromStream = async function(fileName, readStream) {
const params = {
Bucket: bucket,
Key: fileName,
Body: readStream
};
return await s3.upload(params).promise();
};