SeoCache

Cache dedicated for SEO with Javascript rendering :fire:

Purpose

Google credo is: Don't waste my bot time!

So to reduce Googlebot crawling time, let's provide HTML files in a specific cache.

This cache is suitable for static (generated or not) pages but not for connected pages.

Installation

Add this line to your application's Gemfile:

gem 'seo_cache'

And then execute:

$ bundle

Or install it yourself as:

$ gem install seo_cache

Install chromium or chrome driver on your device (the chromedriver will be automatically downloaded).

Declare the middleware. For instance in config/initializers/seo_cache.rb:

require 'seo_cache'

# See options below

Rails.application.config.middleware.use SeoCache::Middleware

Options

Chrome path (required) (disk or memory):

SeoCache.chrome_path = Rails.env.development? ? '/usr/bin/chromium-browser' : '/usr/bin/chromium'

Choose a cache mode (memory (default) or disk):

SeoCache.cache_mode = 'memory'

Cache path (required):

SeoCache.cache_path = Rails.root.join('public', 'seo_cache')

Redis URL (required if memory cache):

SeoCache.redis_url = "redis://localhost:6379/"

Redis prefix:

SeoCache.redis_namespace = '_my_project:seo_cache'

Waiting time before the page is fully loaded (optional in sec, useful for async elements):

SeoCache.wait_time_for_page_loading = 3

Specific log file (if you want to log missed cache urls):

SeoCache.logger_path = Rails.root.join('log', 'seo_cache.log')

Activate missed cache urls:

SeoCache.log_missed_cache = true

Domains to whitelist (authorize only domains which contains these hosts):

SeoCache.whitelist_hosts = []

URLs to blacklist:

SeoCache.blacklist_params = %w[^/assets/.* ^/admin.*]

Params to blacklist:

SeoCache.blacklist_urls = %w[page]

URLs to whitelist:

SeoCache.whitelist_urls = []

Cache page even if user is connected (be careful when caching sensitive data):

SeoCache.cache_with_user_connected = true

Parameter to add manually to the URl to force page caching, if you want to cache a specific URL (e.g. https://<my_website>/?_seo_cache_=true):

SeoCache.force_cache_url_param = '_seo_cache_'

Cache only the pages with these HTTP status code (don't cache by default not found or error pages):

SeoCache.cache_only_status = [<your_list>]

URL extension to ignore when caching (already defined):

SeoCache.extensions_to_ignore = [<your_list>]

List of bot agents (already defined):

SeoCache.crawler_user_agents = [<your_list>]

Parameter added to URL when generating the page, avoid infinite rendering (override only if already used):

SeoCache.prerender_url_param = '_prerender_'

If you encounter the following error DevToolsActivePort file doesn't exist, you can add the following option:

SeoCache.chrome_debugging_port = '9222'

Be aware, JS will be rendered twice: once by server rendering and once by client. For React, this not a problem but with jQuery plugins, it can duplicate elements in the page (you have to check the redundancy).

Disk cache is recommended by default. Nginx will directly fetch file on disk. The TTFB (time to first byte) will be under 200ms :). You can use memory cache if you have lot of RAM.

Controllers

You can check if seo mode is active in your controllers, with the following variable:

request.env['seo_mode']

Consult cache pages

Too see in browser the cache page, open a browser and set the user agent to:

Googlebot (Mozilla/5.0 (compatible; Googlebot/2.1; +http://www.google.com/bot.html))

For instance, with Chrome or Chromium, you can change the user agent in "Network conditions" panel.

To (re)cache a page, add this parameter to the url (the browser must use the Googlebot user agent):

/?_seo_cache_=true

Automatic caching

To automate caching, create a cron rake task (e.g. in lib/tasks/populate_seo_cache.rake):

namespace :MyProject do

  desc 'Populate cache for SEO'
  task populate_seo_cache: :environment do |_task, _args|
    require 'seo_cache/populate_cache'

    paths_to_cache = public_paths_like_sitemap

    SeoCache::PopulateCache.new('https://<your-domain-name>', paths_to_cache).new.perform
  end
end

You can add the force_cache: true option to SeoCache::PopulateCache for overwrite cache data.

If you want to only execute only through a rake task, you can comment the line which include the middleware. keep all options configured and remove only the middleware. Thus all pages will be cached and SeoCache not called for pages not in cache. It's useful if you have a script which generates all website pages (based on sitemap for instance) and you run script every day.

Server

If you use disk caching, add to your Nginx configuration:

# Before any block:
map $http_user_agent $limit_bots {
    default 0;
    ~*(google|bing|yandex|msnbot) 1;
}

map $request_method $is_get {
    default 0;
    GET 1;
}

# Before location block:
set $bot_request '';
if ($is_get) {
      set $bot_request 'GET_';
}

if ($limit_bots) { 
  set $bot_request "${bot_request}BOT"; 
}

set $cache_extension '';
if ($bot_request = GET_BOT) {
  set $cache_extension '.html';
}

# Inside location block:
location / {
    # Ignore url with blacklisted params (e.g. page)
    if ($arg_page) {
      break;
    }
    if ($arg__seo_cache_) {
      break;
    }

    # Local rewrite to remove trailing slash
    rewrite ^/(.*)/$ /$1 last;

    try_files /seo_cache/$uri/index$cache_extension /seo_cache/$uri$cache_extension /seo_cache/$uri $uri @rubyproxy;
}

location @rubyproxy {
    ...
}

This configuration allow you to use SEO cache only for bots (you can add other bots) and GET requests. For users, you don't want to use the cached page (user connection, basket, ...). The performance are less important for users then bots.

Heroku case

If you use Heroku server, you can't store file on dynos. But you have two alternatives :

• Use the memory mode

• Use a second server (a dedicated one) to store HTML files and combine with Nginx.

To intercept the request, use the following middleware in Rails:

In config/initializers, create a new file:

require 'bot_detector'

if Rails.env.production?
  Rails.application.config.middleware.insert_before ActionDispatch::Static, BotDetector
end

Then in lib directory, for instance, manage the request:

class BotRedirector
  CRAWLER_USER_AGENTS = ['googlebot', 'yahoo', 'bingbot', 'baiduspider', 'facebookexternalhit', 'twitterbot', 'rogerbot', 'linkedinbot', 'embedly', 'bufferbot', 'quora link preview', 'showyoubot', 'outbrain', 'pinterest/0.', 'developers.google.com/+/web/snippet', 'www.google.com/webmasters/tools/richsnippets', 'slackbot', 'vkShare', 'W3C_Validator', 'redditbot', 'Applebot', 'WhatsApp', 'flipboard', 'tumblr', 'bitlybot', 'SkypeUriPreview', 'nuzzel', 'Discordbot', 'Google Page Speed', 'Qwantify'].freeze

  IGNORE_URLS = [
    '/robots.txt'
  ].freeze

  def initialize(app)
    @app = app
  end

  def call(env)
    if env['HTTP_USER_AGENT'].present? && CRAWLER_USER_AGENTS.any? { |crawler_user_agent| env['HTTP_USER_AGENT'].downcase.include?(crawler_user_agent.downcase) }
      begin
        request = Rack::Request.new(env)

        return @app.call(env) if IGNORE_URLS.any? { |ignore_url| request.fullpath.downcase =~ /^#{ignore_url.downcase}/ }

        url     = URI.parse(ENV['SEO_SERVER'] + request.fullpath)
        headers = {
          'User-Agent'      => env['HTTP_USER_AGENT'],
          'Accept-Encoding' => 'gzip'
        }
        req     = Net::HTTP::Get.new(url.request_uri, headers)
        # req.basic_auth(ENV['SEO_USER_ID'], ENV['SEO_PASSWD']) # if authentication mechanism
        http         = Net::HTTP.new(url.host, url.port)
        http.use_ssl = true if url.scheme == 'https'
        response     = http.request(req)
        if response['Content-Encoding'] == 'gzip'
          response.body              = ActiveSupport::Gzip.decompress(response.body)
          response['Content-Length'] = response.body.length
          response.delete('Content-Encoding')
        end

        return [response.code.to_i, { 'Content-Type' => response.header['Content-Type'] }, [response.body]]
      rescue => error
        Rails.logger.error("[bot_redirection] #{error.message}")

        @app.call(env)
      end
    else
      @app.call(env)
    end
  end
end

If you use a second server, all links must be relatives in your HTML files, to avoid multi-domains links.

Inspiration

Inspired by prerender gem.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/floXcoder/seo_cache. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the Contributor Covenant code of conduct.

License

The gem is available as open source under the terms of the MIT License.

Code of Conduct

Everyone interacting in the SeoCache project’s codebases, issue trackers, chat rooms and mailing lists is expected to follow the code of conduct.