Humid

Humid is a lightweight wrapper around mini_racer and webpacker used to generate Server Side Rendered (SSR) pages from your javascript application. While it was built for React, it can work with any JS function that returns a HTML string.

Caution

This project is in its early phases of development. Its interface, behavior, and name are likely to change drastically before a major version release.

Installation

Add Humid to your Gemfile.

gem 'humid'

For source-map support, also add

yarn add source-map-support

Configuration

Add an initializer to configure

Humid.configure do |config|
  # Name of your webpacker pack file located in `app/javascript/packs/`. You
  # should use a separate pack from your `application.js`.
  #
  # Defaults to "server_rendering.js"
  config.server_rendering_pack = "server_rendering.js"

  # Name of your webpacker pack source map.
  #
  # Defaults to `false`
  config.use_source_map = true

  # Raise errors if JS rendering failed. If false, the error will be
  # logged out to Rails log and Humid.render will return an empty string
  #
  # Defaults to true.
  config.raise_render_errors = Rails.env.development? || Rails.env.test?

  # The logger instance.
  # `console.log` and friends (`warn`, `error`) are delegated to
  # the respective logger levels on the ruby side.
  #
  # Defaults to `Logger.new(STDOUT)`
  config.logger = Rails.logger

  # Options passed to mini_racer.
  #
  # Defaults to empty `{}`.
  config.context_options = {
    timeout: 1000,
    ensure_gc_after_idle: 2000
  }
end

# Common development options
if Rails.env.development? || Rails.env.test?
  # Use single_threaded mode for Spring and other forked envs.
  MiniRacer::Platform.set_flags! :single_threaded

  # If you're using Puma in single mode:
  Humid.create_context
end

If you'd like support for source map support, you will need to

Ensure config.use_source_map is set to true
Add the following to your server_rendering.js pack.

require("source-map-support").install({
  retrieveSourceMap: filename => {
    return {
      url: filename,
      map: readSourceMap(filename)
    };
  }
});

The mini_racer environment.

Functions not available

The following functions are not available in the mini_racer environment

setTimeout
clearTimeout
setInterval
clearInterval
setImmediate
clearImmediate

`console.log`

console.log and friends (info, error, warn) are delegated to the respective methods on the configured logger.

Usage

Pass your HTML render function to setHumidRenderer

// Set a factory function that will create a new instance of our app
// for each request.
setHumidRenderer((json) => {
  const initialState = JSON.parse(json)

  return ReactDOMServer.renderToString(
    <Application initialPage={initialState}/>
  )
})

And finally call render from ERB.

<%= Humid.render(initial_state) %>

Instrumentation is included:

Completed 200 OK in 14ms (Views: 0.2ms | Humid SSR: 11.0ms | ActiveRecord: 2.7ms)

Puma

mini_racer is thread safe, but not fork safe. To use with web servers that employ forking, use Humid.create_context only on forked processes.

# Puma
on_worker_boot do
  Humid.create_context
end

on_worker_shutdown do
  Humid.dispose
end

Server-side libraries that detect node.js envs.

You may need webpacker to create aliases for server friendly libraries that can not detect the mini_racer environment.

 // config/webpack/production.js
 // config/webpack/development.js
 // config/webpack/test.js

 process.env.NODE_ENV = process.env.NODE_ENV || 'development'

 const environment = require('./environment')
+const path = require('path')
+const ConfigObject = require('@rails/webpacker/package/config_types/config

-module.exports = environment.toWebpackConfig()
+const webConfig = environment.toWebpackConfig()
+const ssrConfig = new ConfigObject(webConfig.toObject())
+
+ssrConfig.delete('entry')
+ssrConfig.merge({
+  entry: {
+    server_rendering: webConfig.entry.server_rendering
+  },
+  resolve: {
+    alias: {
+      'html-dom-parser': path.resolve(__dirname, '../../node_modules/html-dom-parser/lib/html-to-dom-server')
+    }
+  }
+})
+
+delete webConfig.entry.server_rendering
+module.exports = [ssrConfig, webConfig]

Writing universal code

Vue has an amazing resource on how to write universal code. Below are a few highlights that are important to keep in mind.

State

Humid uses a single context across multiple request. To avoid state pollution, we provide a factory function to setHumidRenderer that builds a new app instance on every call.

This provides better isolation, but as it is still a shared context, polluting global is still possible. Be careful of modifying global in your code.

Polyfills

Polyfills will fail when using in the mini_racer environment because of missing browser APIs. Account for this by moving the require to componentDidMount in your component.

componentDidMount() {
  const dialogPolyfill = require('dialog-polyfill').default
  dialogPolyfill.registerDialog(this.dialog.current)
  this.dialog.current.open = this.props.open
  this.dialog.current.showModal()
}

Contributing

Please see CONTRIBUTING.md.

License

About thoughtbot

thoughtbot

Humid is maintained and funded by thoughtbot, inc. The names and logos for thoughtbot are trademarks of thoughtbot, inc.

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