Rails - How to check for online users?

Question

What is the best way checking how many users that are current online on a page?

Answer 1

Keep in Redis

Like Yuri Barbashow's answer but using Redis (nice introdution for Rails):

# config/initializers/redis.rb

$redis_onlines = Redis.new
# it's the simplest way, but i'd recommend:
# $redis_onlines = Redis.new path: "/tmp/redis.sock", db: 15, driver: :hiredis
# => hiredis driver more fast
# => use unix domain socket if it's possible
# => default db is No.0, but it is better to use a specific database
#    and No.0 leave for testing-development-and-more-and-more

Gemfile

# Gemfile

gem 'redis'
gem 'hiredis' # optional
# don't forget to run `bundle`

Set to online

# app/controllers/application_controller.rb
after_filter :set_online
# the Rails 4 way is:
# after_action :set_online

private

  # set to online
  def set_online
    if !!current_user
      # using separate Redis database
      # such as $redis_onlines = Redis.new db: 15
      # value not need, only key
      $redis_onlines.set( current_user.id, nil, ex: 10*60 )
      # 'ex: 10*60' - set time to live - 10 minutes
    end
  end

Is online?

# app/models/user.rb

def online?
  $redis_onlines.exists( self.id )
end

And small bonus (if you are using separate redis database)

# app/cpntrollers/application_controller.rb

def all_who_are_in_touch
  $redis_onlines.keys
  # => [ "123", "234", "1", "23" ]
  # array of ids
end

---

#UDP1 rework for anonymous

Set to online

# app/controllers/application_controller.rb

  def set_online
    if !!current_user
      $redis_onlines.set( "user:#{current_user.id}", nil, ex: 10*60 )
    else
      $redis_onlines.set( "ip:#{request.remote_ip}", nil, ex: 10*60 )
    end
  end

Is online?

# app/models/user.rb

def online?
  $redis_onlines.exists( "user:#{self.id}" )
end

All who are in touch:

# app/cpntrollers/application_controller.rb

def all_signed_in_in_touch
  ids = []
  $redis_onlines.scan_each( match: 'user*' ){|u| ids << u.gsub("user:", "") }
  ids
end

def all_anonymous_in_touch
  $redis_onlines.scan_each( match: 'ip*' ).to_a.size
end

def all_who_are_in_touch
  $redis_onlines.dbsize
end

---

#UDP2 Recommendations

1. Use a before_filter instead of a after_filter

# app/controllers/application_controller.rb
  before_filter :set_online # before_action for Rails 4

2. If you watch the anonymous (for example session[:user_id] is id of current user)

# app/controllers/session_controller.rb
  before_filter :clear_from_signed_in_touch, only: :destroy
  before_filter :clear_from_anonymous_in_touch, only: :create

  private

    def clear_from_anonymous_in_touch
      $redis_onlines.del( "ip:#{request.remote_ip}" )
    end

    def clear_from_signed_in_touch
      $redis_onlines.del( "user:#{session[:user_id]}" )
    end

Postscript: Redis | set | exists | expire | scan | scan_each | redis-rb | hiredis | nice introduction for beginners

Answer 2

The simplest thing would be to add a last_online timestamp to your User model, then define a scope for user called online_now

class User < ActiveRecord::Base
  def self.online_now
    where("last_online > ?", 15.minutes.ago)
  end
end