FIX: TopicLinkClick: do not log IP of logged in users

app/models/topic_link_click.rb

@@ -7,7 +7,6 @@ class TopicLinkClick < ActiveRecord::Base
   belongs_to :user
 
   validates_presence_of :topic_link_id
-  validates_presence_of :ip_address
 
   WHITELISTED_REDIRECT_HOSTNAMES = Set.new(%W{www.youtube.com youtu.be})
 
@@ -108,6 +107,7 @@ class TopicLinkClick < ActiveRecord::Base
     rate_key = "link-clicks:#{link.id}:#{args[:user_id] || args[:ip]}"
     if $redis.setnx(rate_key, "1")
       $redis.expire(rate_key, 1.day.to_i)
+      args[:ip] = nil if args[:user_id]
       create!(topic_link_id: link.id, user_id: args[:user_id], ip_address: args[:ip])
     end
 
@@ -125,7 +125,7 @@ end
 #  user_id       :integer
 #  created_at    :datetime         not null
 #  updated_at    :datetime         not null
-#  ip_address    :inet             not null
+#  ip_address    :inet
 #
 # Indexes
 #

db/migrate/20180521190040_allow_null_ip_topic_link_click.rb

@@ -0,0 +1,10 @@
+class AllowNullIpTopicLinkClick < ActiveRecord::Migration[5.1]
+  def up
+    begin
+      Migration::SafeMigrate.disable!
+      change_column :topic_link_clicks, :ip_address, :inet, null: true
+    ensure
+      Migration::SafeMigrate.enable!
+    end
+  end
+end