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Webpack dev server and Rails on Cloud9

Please note that this article is particularly relevant when migrating the webpacker gem from v3.0.1 to v3.0.2, as described in the below.

[Go to tl;dr]

Contents

Context

This article describes how to properly configure webpack-dev-server with webpacker gem on a Cloud9 workspace. After a preliminary remark about the proper binstub version of the ./bin/webpack-dev-server script, this article presents two ways to tackle the task: a simple and quick solution, which is sufficient if we work alone on a project, and a slightly more involved but flexible approach, that can be useful when several people might work in the same codebase.

Binstub versions

A lot of the confusion about the webpack-dev-server options and why they might not be properly taken into account, might be due to an outdated version of the ./bin/webpack-dev-server script. The script created by the rails webpacker:install task of the webpacker gem v3.0.1 (source) is not compatible with how v3.0.2 (sic) of the gem handles the webpack-dev-server option flags (see full list of versions below), which logically expects the corresponding binstub version of the script (source). So please make sure that you are using the correct binstub (the same applies to ./bin/webpack). To be fair, the changelog of v3.0.2 properly mentions the change:

  • Added: Binstubs #833
  • (...)
  • Removed: Inline CLI args for dev server binstub, use env variables instead

Quick solution

If you are working alone, the easiest way to fix the configuration of the webpack-dev-server is to modify the development.dev_server entry of the config/webpacker.yml file.

config/webpacker.yml file

The development.dev_server entry of the config/webpacker.yml file has to be changed from the following default values:

dev_server:
  https: false
  host: localhost
  port: 3035
  public: localhost:3035
  hmr: false
  # Inline should be set to true if using HMR
  inline: true
  overlay: true
  disable_host_check: true
  use_local_ip: false

into these custom configuration:

dev_server:
  https: true
  host: localhost
  port: 8082
  public: your-workspace-name-yourusername.c9users.io:8082
  hmr: false
  inline: false
  overlay: true
  disable_host_check: true
  use_local_ip: false

You can obtain the value your-workspace-name-yourusername.c9users.io for your Cloud9 workspace with echo ${C9_HOSTNAME}.

There are four main differences with the approaches found in the mentioned sources:

  • Some solutions suggested to set the host option to your-workspace-name-yourusername.c9users.io, which required to add a line to the /etc/hosts file by running echo "0.0.0.0 ${C9_HOSTNAME}" | sudo tee -a /etc/hosts. This was only necessary due to restrictions in previous versions of webpacker and how the value of the public setting was calculated. Currently it is no longer necessary to modify the /etc/hosts file because the host setting can be kept as localhost.

  • Some solutions stressed the need to set the https option to false but this failed with net::ERR_ABORTED in the browser console and raised the following exception in the server when the client tried to get the JavaScript sources:

    #<OpenSSL::SSL::SSLError: SSL_connect SYSCALL returned=5 errno=0 state=unknown state>

    Setting https: true removes the issue.

  • By leaving the inline option to the default false value, the live compilation still works but the browser console constantly reports the following error:

    Failed to load https://your-workspace-name-yourusername.c9users.io:8082/sockjs-node/info?t=1511016561187: No 'Access-Control-Allow-Origin' header is present on the requested resource.
Origin 'https://your-workspace-name-yourusername.c9users.io' is therefore not allowed access. The response had HTTP status code 503.

    Setting inline: false removes the issue.

  • None of the solutions suggested to set the public option in the config/webpacker.yml file and some suggested to pass it to the webpack-dev-server command line. By setting it in the configuration file we don't need to care about it in the terminal.

With this configuration, running as usual ./bin/webpack-dev-server in one terminal and ./bin/rails s -b $IP -p $PORT in another should work.

Flexible solution

The previous solution is useful and fast to implement, but if you are working with other people on the same repo it can be tricky to maintain the proper configuration in the config/webpacker.yml file. Moreover, the hostname of your Cloud9 workspace is hardcoded, so that the configuration is not portable.

A hint about another way to configure the webpack-dev-server can be found in the README of this repo:

You can use environment variables as options supported by webpack-dev-server in the form WEBPACKER_DEV_SERVER_<OPTION>. Please note that these environment variables will always take precedence over the ones already set in the configuration file.

Note that when the configuration of the webpack-dev-server is tweaked with ENV variables, those same values have to be passed to the rails server process as well in order to let it use the same configuration.

Taking that into account, a flexible solution can be implemented using foreman with the following Procfile.dev:

web:        ./bin/rails server -b ${RAILS_SERVER_BINDING:-localhost} -p ${RAILS_SERVER_PORT:-3000}
webpacker:  ./bin/webpack-dev-server

and this bin/start script:

#!/bin/bash

# Immediately exit script on first error
set -e -o pipefail

APP_ROOT_FOLDER="$( cd "$( dirname "${BASH_SOURCE[0]}" )/.." && pwd )"
cd "${APP_ROOT_FOLDER}"

if [ -n "${C9_USER}" ]; then
  # We are in a Cloud9 machine

  # Make sure that Postgres is running
  sudo service postgresql status || sudo service postgresql start

  # Adapt the configuration of the webpack-dev-server
  export APP_DOMAIN="${C9_HOSTNAME}"
  export RAILS_SERVER_BINDING='0.0.0.0'
  export RAILS_SERVER_PORT='8080'
  export WEBPACKER_DEV_SERVER_PORT='8082'
  export WEBPACKER_DEV_SERVER_HTTPS='true'
  export WEBPACKER_DEV_SERVER_HOST="localhost"
  export WEBPACKER_DEV_SERVER_PUBLIC="${C9_HOSTNAME}:${WEBPACKER_DEV_SERVER_PORT}"
  export WEBPACKER_DEV_SERVER_HMR='false'
  export WEBPACKER_DEV_SERVER_INLINE='false'
  export WEBPACKER_DEV_SERVER_OVERLAY='true'
  export WEBPACKER_DEV_SERVER_DISABLE_HOST_CHECK='true'
  export WEBPACKER_DEV_SERVER_USE_LOCAL_IP='false'
fi

foreman start -f Procfile.dev

With these two scripts in place, the application can always be started by running bin/start, in both Cloud9 and other systems. The trick is that by exporting the WEBPACKER_DEV_SERVER_* variables before calling foreman start, we make sure that those values are available to both webpack-dev-server and rails server processes.

Sources

Versions

Since things in this ecosystem move fast, it's important to mention the versions of the world for which this documentation is relevant:

$ egrep '^    ?(ruby|webpacker|rails) ' Gemfile.lock
    rails (5.1.4)
    webpacker (3.0.2)
  ruby 2.4.2p198

$ yarn versions
yarn versions v1.1.0
{ http_parser: '2.7.0',
  node: '8.5.0',
  v8: '6.0.287.53',
  uv: '1.14.1',
  zlib: '1.2.11',
  ares: '1.10.1-DEV',
  modules: '57',
  nghttp2: '1.25.0',
  openssl: '1.0.2l',
  icu: '59.1',
  unicode: '9.0',
  cldr: '31.0.1',
  tz: '2017b' }

$ cat /etc/os-release | head -6
NAME="Ubuntu"
VERSION="14.04.5 LTS, Trusty Tahr"
ID=ubuntu
ID_LIKE=debian
PRETTY_NAME="Ubuntu 14.04.5 LTS"
VERSION_ID="14.04"

Everything was tested using Chrome Version 62.

tl;dr

  1. Make sure that you are running the proper binstub version of ./bin/webpack-dev-server.

  2. Change the development.dev_server entry config/webpacker.yml file into:

    dev_server:
  https: true
  host: localhost
  port: 8082
  public: your-workspace-name-yourusername.c9users.io:8082
  hmr: false
  inline: false
  overlay: true
  disable_host_check: true
  use_local_ip: false

  3. Now running as usual ./bin/webpack-dev-server in one terminal and ./bin/rails s -b $IP -p $PORT in another should work as expected.