added user activities redis logic

app/models/user.rb

@@ -948,9 +948,7 @@ class User < ActiveRecord::Base
   end
 
   def record_activity
-    Gitlab::Redis.with do |redis|
-      redis.zadd('user/activities', Time.now.to_i, self.username)
-    end
+    Gitlab::UserActivities.record(self)
   end
 
   private

lib/gitlab/user_activities.rb

+module Gitlab
+  class UserActivities
+    KEY = 'user/activities'
+    DEFAULT_PAGE_SIZE = 50
+
+    def self.record(user)
+      Gitlab::Redis.with do |redis|
+        redis.zadd(KEY, Time.now.to_i, user.username)
+      end
+    end
+
+    def self.query(*args)
+      new(*args).query
+    end
+
+    def initialize(from: 6.months.ago, page: 0, per_page: DEFAULT_PAGE_SIZE)
+      @from = from
+      @page = page
+      @per_page = per_page
+    end
+
+    def query
+      Gitlab::Redis.with do |redis|
+        redis.zrangebyscore(KEY, @from.to_i, Time.now.to_i, with_scores: true, limit: [offset, @per_page])
+      end
+    end
+
+    private
+
+    def offset
+      @page * @per_page
+    end
+  end
+end