SLS webpack invoke (v2) + SLS invoke local (V3) don't terminate once the response has been sent

This is a Bug Report

Description

I’m trying to run sls webpack invoke -f some_function inside a docker container, but the command hangs and I have to stop the machine in another terminal window. Hitting Ctrl+C/D doesn’t work. I’m getting Docker to do it as it’s part of a Jenkins pipeline, and that’s how other devs are doing this in my company.

I expect sls webpack invoke -f some_function to terminate once the callback has been executed. I’m not running it with the --watch flag.

I’ve tried upgrading to 2.2.2, but I get the same issue (still using sls webpack invoke -f some_function even though the docs say it’s been disabled). I cannot run sls invoke local as I get SyntaxError: Unexpected token import as webpack hasn’t actually done anything

My serverless.yml has the following plugins

plugins:
  - serverless-webpack
  - serverless-offline (Even with this turned off, it makes no difference)
  - serverless-jest-plugin (Even with this turned off, it makes no difference)

That is the exact order, and I’ve seen mention of webpack needing to be first, and it already is

Additional Data

Serverless-Webpack 2.2.0 (And 2.2.2) Webpack 3.5.4 Serverless-Offline 3.15.3 Serverless 1.20.2 OS: OS X (local) / Ubuntu (docker)

Stack Trace

(function (exports, require, module, __filename, __dirname) { import { successResponse } from '../helpers'
                                                              ^^^^^^
SyntaxError: Unexpected token import
    at createScript (vm.js:56:10)
    at Object.runInThisContext (vm.js:97:10)
    at Module._compile (module.js:542:28)
    at Object.Module._extensions..js (module.js:579:10)
    at Module.load (module.js:487:32)
    at tryModuleLoad (module.js:446:12)
    at Function.Module._load (module.js:438:3)
    at Module.require (module.js:497:17)
    at require (internal/module.js:20:19)
    at AwsInvokeLocal.invokeLocalNodeJs (/usr/local/lib/node_modules/serverless/lib/plugins/aws/invokeLocal/index.js:156:33)
    at AwsInvokeLocal.invokeLocal (/usr/local/lib/node_modules/serverless/lib/plugins/aws/invokeLocal/index.js:114:19)
    at AwsInvokeLocal.tryCatcher (/usr/local/lib/node_modules/serverless/node_modules/bluebird/js/release/util.js:16:23)
    at Promise._settlePromiseFromHandler (/usr/local/lib/node_modules/serverless/node_modules/bluebird/js/release/promise.js:512:31)
    at Promise._settlePromise (/usr/local/lib/node_modules/serverless/node_modules/bluebird/js/release/promise.js:569:18)
    at Promise._settlePromise0 (/usr/local/lib/node_modules/serverless/node_modules/bluebird/js/release/promise.js:614:10)
    at Promise._settlePromises (/usr/local/lib/node_modules/serverless/node_modules/bluebird/js/release/promise.js:693:18)
    at Async._drainQueue (/usr/local/lib/node_modules/serverless/node_modules/bluebird/js/release/async.js:133:16)
    at Async._drainQueues (/usr/local/lib/node_modules/serverless/node_modules/bluebird/js/release/async.js:143:10)
    at Immediate.Async.drainQueues (/usr/local/lib/node_modules/serverless/node_modules/bluebird/js/release/async.js:17:14)
    at runCallback (timers.js:672:20)
    at tryOnImmediate (timers.js:645:5)
    at processImmediate [as _immediateCallback] (timers.js:617:5)

webpack.config.js

const path = require('path')
const slsw = require('serverless-webpack')

require('source-map-support').install()

module.exports = {
  entry: slsw.lib.entries,
  devtool: 'source-map',
  target: 'node',
  externals: [
    /aws-sdk/ // Available on AWS Lambda
  ],
  module: {
    rules: [
      {
        test: /\.js$/,
        exclude: /node_modules/,
        loader: 'babel-loader'
      }
    ]
  },
  output: {
    libraryTarget: 'commonjs',
    path: path.join(__dirname, '.webpack'),
    filename: '[name].js'
  }
}

babelrc

{
  "presets" : [
    [
      "env",
      {
        "presets": [
          "stage-3"
        ],
        "targets": {
          "node": "6.10"
        },
        "useBuiltIns": true,
        "modules": false,
        "loose": true
      }
    ]
  ],
  "plugins":[
    [
      "transform-async-to-module-method",
      {
        "module": "bluebird",
        "method": "coroutine"
      }
    ]
  ]
}

[btaylor-ihr]

Thanks for the quick response! I posted this before I left work, so I’ll have a look at this in the morning.

The lingering objects might actually be a big clue. I’m not closing my db connection because I’ve been running into bugs if I do close the connection. I’m new to Promises and async/await. I’m not closing my database connection because there are queries that are somehow firing after the db gets closed. Serverless offline holds my hand there (somehow), but maybe that’s all I need to fix 😃

I’ll update you tomorrow

[HyperBrain]

I tested it with two different projects of ours (with 3.0.0-rc.2). One project terminates correctly after showing the lambda results, one project does not. It looks for me now that the node main loop waits for an empty state and thus does not end the node process correctly. The tests were done in a bash shell, so the problem is independent from Docker.

I used serverless invoke local --function=<function> --path=<test event json> (the same should happen with v2 and webpack invoke)

The project that terminates correctly does not use any global lingering objects, the other one that does not terminate, uses a global REDIS connection that still executes at the end. In AWS Lambda the behavior is that we configure the lambda to exit as soon as the final callback is called and not wait for the event loop to be empty. I’m pretty sure that that’s the core of the problem - the plugin must exit as soon as the terminating lambda callback has been called and the handler exits.