AWS Lambda - downloading a file, and using it in the same function - nodejs

Question

I have some certificate files over s3 (public) and I am to download and use these files in my code, If I write an equivalent code in nodejs at my local, it just runs fine, but in AWS lambda it just crashes.

var apn = require('apn'); var https = require('https'); var fs = require('fs');  exports.handler = function(event, context) {   console.log("Running aws apn push message function");   console.log("==================================");   console.log("event", event);    var certPath = event.certPath;   var keyPath = event.keyPath;   var certFileName = event.certFileName;   var keyFileName = event.keyFileName;   var passphrase = event.passphrase;   var apnId = event.apnId;   var content = event.content;   var certfile = fs.createWriteStream(certFileName); var certrequest = https.get(certPath, function(certresponse) {   certresponse.pipe(certfile);   console.log("downloaded the certificate");    var keyfile = fs.createWriteStream(keyFileName);   var keyrequest = https.get(keyPath, function(keyresponse) {     keyresponse.pipe(keyfile);     console.log("downloaded the key file");     var options = {                        "cert":certFileName,                       "key":keyFileName,                       "passphrase":passphrase,                       "batchFeedback": true,                       "interval": 10                       };    var apnConnection = new apn.Connection(options);    var myDevice = new apn.Device(apnId);   var note = new apn.Notification();   note.expiry = Math.floor(Date.now() / 1000) + 3600; // Expires 1 hour from now.           note.payload = {'COMMAND': content};          apnConnection.pushNotification(note, myDevice);   console.log('message sent to ' + apnId);           context.done();    }); }); } 

Error I get is related to accessing files i suppose -

events.js:72   throw er; // Unhandled 'error' event   ^  Error: EACCES, open 'PushChatCert.pem' 

So while on AWS Lambda is there some specific concerns when one is downloading a file and using it, related to its path or something, where do the files stay when they get downloaded, in fact I don't even see the log of file getting downloaded.

Answer 1

The only available local file system you can write to in Lambda is /tmp so make sure the path for the local file you are trying to write to is in the /tmp directory and you should be all set.

Answer 2

Just note as of last year (2020) Lambdas support EFS as a mount as well so you can write to EFS mount point. Excessive for your case..but it might help for someone doing large file processing https://aws.amazon.com/blogs/compute/using-amazon-efs-for-aws-lambda-in-your-serverless-applications/