aws-serverless-express + serverless-offline plugin = server error listen EACCES /tmp/server0.sock

I am experimenting running the aws-serverless-express module in combination with the serverless-offline plugin for the serverless framework. This combination results in a critical error upon sending the request to the corresponding path and not when the serverless offline start command is run. Testing the offline plugin with another route not using the aws-serverless-express module runs fine and gives me a response. This is what I have:

package.json

{
  "name": "ExpresssLambdaServerless",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {},
  "keywords": [],
  "author": "",
  "license": "ISC",
  "dependencies": {
    "aws-serverless-express": "^3.0.2",
    "express": "^4.16.2"
  },
  "devDependencies": {
    "serverless-offline": "^3.16.0"
  }
}

serverless.yml

service: aws-nodejs 
provider:
  name: aws
  runtime: nodejs6.10
functions:
  helloExpress:
    handler: index.handlerExpress
    events:
      - http: GET express
  helloPlain:
    handler: index.handlerPlain
    events:
      - http: GET plain
plugins:
  - serverless-offline

index.js

'use strict';
const awsServerlessExpress = require('aws-serverless-express');
const app = require('./app');
const server = awsServerlessExpress.createServer(app);

// does NOT work
exports.handlerExpress = (event, context, callback) => awsServerlessExpress.proxy(server, event, callback);
// works
exports.handlerPlain = (event, context, callback) => {

	callback(null, { 
		statusCode: 200, 
		body: JSON.stringify({
		 works: true
		}) 
	});
};

app.js

'use strict';
const express = require('express');
const awsServerlessExpressMiddleware = require('aws-serverless-express/middleware');
const app = express();
app.get('/express', (req, res) => {
  
  res.status(200).json({
    works: false
  });
});
module.exports = app;

Console output:

Git bash as admin on Windows 10

node -v: v8.9.0

$ sls offline start
Serverless: Starting Offline: dev/us-east-1.

Serverless: Routes for helloExpress:
Serverless: GET /express

Serverless: Routes for helloPlain:
Serverless: GET /plain

Serverless: Offline listening on http://localhost:3000

Serverless: GET /plain (λ: helloPlain)
Serverless: The first request might take a few extra seconds
Serverless: [200] {"statusCode":200,"body":"{\"works\":true}"}

Serverless: GET /express (λ: helloExpress)
Serverless: The first request might take a few extra seconds
ERROR: server error
{ Error: listen EACCES /tmp/server0.sock
    at Object._errnoException (util.js:1024:11)
    at _exceptionWithHostPort (util.js:1046:20)
    at Server.setupListenHandle [as _listen2] (net.js:1334:19)
    at listenInCluster (net.js:1392:12)
    at Server.listen (net.js:1487:5)
    at startServer (my-pc-path\node_modules\aws-serverless-express\index.js:136:19)
    at Object.proxy (my-pc-path\node_modules\aws-serverless-express\index.js:175:16)
    at exports.handlerExpress (my-pc-path\index.js:7:67)
    at handler (my-pc-path\node_modules\serverless-offline\src\index.js:751:25)
    at Object.internals.handler (my-pc-path\node_modules\hapi\lib\handler.js:96:36)
    at request._protect.run (my-pc-path\node_modules\hapi\lib\handler.js:30:23)
    at module.exports.internals.Protect.internals.Protect.run (my-pc-path\node_modules\hapi\lib\protect.js:64:5)
    at exports.execute (my-pc-path\node_modules\hapi\lib\handler.js:24:22)
    at each (my-pc-path\node_modules\hapi\lib\request.js:384:16)
    at iterate (my-pc-path\node_modules\items\lib\index.js:36:13)
    at done (my-pc-path\node_modules\items\lib\index.js:28:25)
    at module.exports.internals.Auth.internals.Auth._authenticate (my-pc-path\node_modules\hapi\lib\auth.js:210:16)
    at internals.Auth.authenticate (my-pc-path\node_modules\hapi\lib\auth.js:202:17)
    at each (my-pc-path\node_modules\hapi\lib\request.js:384:16)
    at iterate (my-pc-path\node_modules\items\lib\index.js:36:13)
    at done (my-pc-path\node_modules\items\lib\index.js:28:25)
    at internals.state (my-pc-path\node_modules\hapi\lib\route.js:357:16)
    at each (my-pc-path\node_modules\hapi\lib\request.js:384:16)
    at iterate (my-pc-path\node_modules\items\lib\index.js:36:13)
    at Object.exports.serial (my-pc-path\node_modules\items\lib\index.js:39:9)
    at internals.Request._lifecycle (my-pc-path\node_modules\hapi\lib\request.js:387:11)
    at internals.Request._execute (my-pc-path\node_modules\hapi\lib\request.js:302:21)
    at Domain.request._protect.enter (my-pc-path\node_modules\hapi\lib\connection.js:261:25)
    at Domain.run (domain.js:242:14)
    at module.exports.internals.Protect.internals.Protect.enter (my-pc-path\node_modules\hapi\lib\protect.js:80:17)
    at Server.<anonymous> (my-pc-path\node_modules\hapi\lib\connection.js:259:30)
    at emitTwo (events.js:126:13)
    at Server.emit (events.js:214:7)
    at parserOnIncoming (_http_server.js:602:12)
    at HTTPParser.parserOnHeadersComplete (_http_common.js:117:23)
  code: 'EACCES',
  errno: 'EACCES',
  syscall: 'listen',
  address: '/tmp/server0.sock',
  port: -1 }

I tried running the serverless-offline plugin on a different port as well with the same result. My assumption is that both the serverless plugin and the aws-serverless-express modules are creating a server using the same resource and this is why it breaks when the express endpoint is called. I also tried changing the tmp path in index.js file of aws-serverless-express to something different, but didn’t work either.

I would highly appreciate some help. PM me if more info is needed. Thanks!!!

[brettstack]

Fixed in 3.1.1

[y13i]

+1

I think _socketPathSuffix should be random value instead of incrementing number. cf. #5

I created a randomized suffix version https://github.com/y13i/aws-serverless-express/tree/feat-randomized-sock-suffix just for test purpose and you can test it with npm install @y13i/aws-serverless-express.

Should I send a pull request with that version?