Can AWS Lambda reach/interact with S/FTP?

Question

I wrote some basic js to just list the files of a FTP but I get:

"Process exited before completing request"

Is that because Lambda can't interact with FTP?

I'm using jsftp btw.

Here's my setup:

• I use Serverless to create the project
• For my lambda, I used nodejs and I'm using JSFTP to deal with the ftp stuff.

My code:

// Require Serverless ENV vars
var ServerlessHelpers = require('serverless-helpers-js').loadEnv();

// Require Logic
var lib = require('../lib');

// Lambda Handler
module.exports.handler = function (event, context) {

    lib.respond(event, function (error, response) {
        return context.done(error, response);
    });
};

My ftp lambda code:

var JSFtp = require("jsftp");

module.exports.respond = function (event, cb) {

    var ftp = new JSFtp({
        host: "host",
        user: "user",
        password: "password"
    });

    ftp.auth(ftp.user, ftp.password, function(err, res) {
        if (err) console.log(err);
        else console.log(res);

        ftp.ls(".", function (err, res) {
            var results = [];
            res.forEach(function (file) {
                results.push(file.name);
            });

            ftp.raw.quit();

            return cb(null, results.length);
        })
    });
};

I added some console.log() all over the place and it seems like it choked once it tried to ftp.auth.

The output I see in cloud watch:

START RequestId: __ID__ Version: $LATEST
END RequestId: __ID__
REPORT RequestId: __ID__    Duration: 526.46 ms Billed Duration: 600 ms     Memory Size: 1024 MB    Max Memory Used: 33 MB  
Process exited before completing request

So it looks like it just choked somewhere...

Solution 1

in short, ftp will not work with lambda since they use ephemeral ports.

sftp will work nicely with lambda. i tested using java code via jsch with no issues; tho i cant see how it wouldnt work with any js sftp lib.

Solution 2

It is possible tested just now. Make sure ur timeout is set to be long enough and you are calling context.succeed() on process termination

function __main__(event, context) {
    var JSFtp = require("jsftp");
    var ftp = new JSFtp({
        host: "speedtest.tele2.net",
        port: 21, // defaults to 21
    });
    ftp.ls(".", function(err, res) {
      var results = []; res.forEach(function(file) {
        results.push(file.name);
      });
      context.succeed(results);
    });
};

Solution 3

By default, Lambda functions only have 3 seconds to complete. If it takes longer than that, you'll get the error you are seeing.

You can adjust the timeout to anything up to 5 minutes. To change it using the aws CLI, run:

aws lambda update-function-configuration --function-name my-lambda-function --timeout 300

Comments

[javamonkey79]

This is not true. Maybe it was when you answered this, so I won't downvote on that presumption. We have FTP transfer code in python working in production AWS Lambda.

[iCodeLikeImDrunk]

not sure if anything has changed since i worked on it. note that this was before vpc was supported. i tried using java and js, didnt check python though.

[Zakir Jaafar]

aws.amazon.com/lambda/faqs says that incoming TCP connections are not allowed. This means FTP PASV won't work at least. Q: What restrictions apply to AWS Lambda function code? ... Inbound network connections are blocked by AWS Lambda, and for outbound connections only TCP/IP sockets are supported, and ptrace (debugging) system calls are restricted. TCP port 25 traffic is also restricted as an anti-spam measure.