Memcached（Dalli客户端） - 可能的内存泄漏？ Heroku的？

Question

我尝试在我的应用中实现低级（模型）缓存。 我正在寻找处理可能的内存泄漏的帮助。

Rails4
client: Dalli
cache store: Memcached Cloud

我有一个'用户'索引页面，我加载了很多用户及其数据（回答了一些问题）。我试图缓存所有这些，因为信息不经常变化。

我注意到每次刷新'用户'页面后，内存占用量一直在增长（直到应用程序超时，因为它达到了heroku的最大限制）

以下是heroku在日志中提供的内存统计信息：

'users' page not yet loaded
heroku[web.1]: sample#memory_total=**147.48MB** sample#memory_rss=147.47MB sample#memory_cache=0.01MB sample#memory_swap=0.00MB sample#memory_pgpgin=38139pages sample#memory_pgpgout=385pages

1st load 'users' page
heroku[web.1]: sample#memory_total=**474.22MB** sample#memory_rss=472.95MB sample#memory_cache=1.27MB sample#memory_swap=0.00MB sample#memory_pgpgin=122341pages sample#memory_pgpgout=941pages

2nd load 'users' page
heroku[web.1]: sample#memory_total=**626.01MB** sample#memory_rss=472.86MB sample#memory_cache=0.00MB sample#memory_swap=153.15MB sample#memory_pgpgin=179711pages sample#memory_pgpgout=58658pages


3rd load 'users' page
heroku[web.1]: sample#memory_total=**631.07MB** sample#memory_rss=484.38MB sample#memory_cache=0.00MB sample#memory_swap=146.69MB sample#memory_pgpgin=199602pages sample#memory_pgpgout=75600pages
heroku[web.1]: Process running mem=631M(123.3%)
heroku[web.1]: Error R14 (Memory quota exceeded)
heroku[router]: at=error code=H12 desc="Request timeout"

同时我正在监视缓存，似乎没有缓存未命中，因此缓存似乎工作正常。

irb(main):098:0> Rails.cache.stats.values_at("total_items", "get_misses","bytes_written","get_hits")
=> ["907", "2721", "92597491", "4535"]
irb(main):099:0> Rails.cache.stats.values_at("total_items", "get_misses","bytes_written","get_hits")
=> ["907", "2721", "111072314", "5442"]
irb(main):100:0> Rails.cache.stats.values_at("total_items", "get_misses","bytes_written","get_hits")
=> ["907", "2721", "129539345", "6155"]

请注意，bytes_written继续增长，这是另一个谜。

以下是相应的缓存代码：

User.rb

  #*********** Caching stuff **********
  def self.cached_find(id)
    #name HERE is class name aka 'User'
    Rails.cache.fetch([name, id]) { find(id) }
  end

  # Statement without .all is lazily evaluated
  # If you add .all, you store actual set of records in your cache.
  def self.approved_user_ids
    Rails.cache.fetch([self,'approved_users']) { where(approved: true).pluck(:id) }
  end


  def answer_cached(q_id)
    Answer.cached_answer(q_id,id)
  end

  def cached_has_any_role?(check_roles)
    assigned_roles = Rails.cache.fetch(['roles', id]) { roles.pluck(:name)}

    #Make sure roles are both string or symbols during comparisons. Be cautious about this since it can lead to wrong permissions
    check_roles.map{|check_role| assigned_roles.include? check_role.to_s}.any?
  end

  def cached_has_role?(check_role)
    assigned_roles = Rails.cache.fetch(['role', id]) {roles.pluck(:name)}

    #Make sure roles are both string or symbols during comparisons. Be cautious about this since it can lead to wrong permissions
    assigned_roles.include? check_role.to_s
  end

  #TODO Couldnt figure out how to flush cache on adding a new role. For now add roles using this method only
  def add_role_flush_cache(*args)
    add_role *args
    flush_roles_from_cache
  end


  // Called on : after_commit :flush_cache
  def flush_cache
    Rails.cache.delete([self.class.name, id])

    Rails.cache.delete(['colleague_ids', id])

    # TODO This invalidates the cache anytime any user record is updated, which is too aggressive.
    # Change it to invalidate only when approved users update their record or new users are approved/disapproved
    Rails.cache.delete(%w(approved_users))
  end

  def flush_roles_from_cache
    Rails.cache.delete(['roles', id])
    Rails.cache.delete(['role', id])
  end

Answer.rb（Model）

class Answer < ActiveRecord::Base
  belongs_to :user, touch:true
  belongs_to :question

  #DO NOT DELETE. This ensures stuff gets flushed out of cache on updates
  after_commit :flush_cache

  #  Caching stuff
  def self.employee_ids_cached(company)
    company_lower = company.downcase
    Rails.cache.fetch([company_lower,16]) { where(question_id: 16).where('lower(content)=?',company_lower).pluck(:user_id) }
  end

  def self.cached_answer(ques_id,u_id)
    Rails.cache.fetch([name,ques_id,u_id]) { where(question_id:ques_id, user_id: u_id).pluck(:content) }
  end

  def flush_cache

    # Delete the entry if a key we used for caching employees is found ([content==company_name and question_id=16])
    # Delete cached employees under a specific company on update to any company
    Rails.cache.delete([content, id])


    #Delete cached answer for the user on updates
    Rails.cache.delete([self.class,question_id,user_id])
  end

end

我不确定此时是否有内存泄漏。但是看起来像Heroku中的内存使用量不断上升，尽管大多数事情都是缓存的，并且是从缓存中服务的。