尝试在 Rails 应用程序中的数据库中保存 ActiveRecord 时出现 NoMethodError

Question

我正在构建的应用程序是一个非常简单的网站监控工具，其中包含用户、警报和抓取。我创建了一个 Rake 任务来负责以指定的时间间隔对站点进行爬网，并且它工作正常，在使用 rake crawl_next 手动运行时将爬网历史保存到数据库中。

在集成逻辑以检查爬网是否超出用户指定的限制或存在错误并通过电子邮件发送给用户后，我不再能够将爬​​网记录保存到数据库中。运行 rake 任务时，我收到了 NoMethodError: undefined method 'clear' for false:FalseClass，但我无法确定其来源。根据控制台输出，我认为这是一些失败的验证，但我无法确定是什么验证可能导致它失败。我希望更有经验的开发人员可以为我指明正确的方向。

我已经隔离了将抓取记录保存到数据库的问题......我想。

• 我使用pry 来检查输入和变量，似乎没有任何问题。
• 我已将抓取模型上的 after_save 操作注释掉，以消除可能的警报模型代码错误。
• 在 Rails 控制台中，我尝试使用质量分配和.create 方法手动创建新爬网。它以同样的方式失败。
• 使用带有 Ruby 2.5.0p0、c9.io IDE 的 Rails 5.1.5

控制台输出：

** Invoke crawl_next (first_time)
** Invoke environment (first_time)
** Execute environment
** Execute crawl_next
rake aborted!
NoMethodError: undefined method `clear' for false:FalseClass
/usr/local/rvm/gems/ruby-2.5.0/gems/activemodel-5.1.5/lib/active_model/validations.rb:334:in `valid?'
/usr/local/rvm/gems/ruby-2.5.0/gems/activerecord-5.1.5/lib/active_record/validations.rb:65:in `valid?'
/usr/local/rvm/gems/ruby-2.5.0/gems/activerecord-5.1.5/lib/active_record/validations.rb:82:in `perform_validations'
/usr/local/rvm/gems/ruby-2.5.0/gems/activerecord-5.1.5/lib/active_record/validations.rb:44:in `save'
/usr/local/rvm/gems/ruby-2.5.0/gems/activerecord-5.1.5/lib/active_record/attribute_methods/dirty.rb:35:in `save'
/usr/local/rvm/gems/ruby-2.5.0/gems/activerecord-5.1.5/lib/active_record/transactions.rb:308:in `block (2 levels) in save'
/usr/local/rvm/gems/ruby-2.5.0/gems/activerecord-5.1.5/lib/active_record/transactions.rb:384:in `block in with_transaction_returning_status'
/usr/local/rvm/gems/ruby-2.5.0/gems/activerecord-5.1.5/lib/active_record/connection_adapters/abstract/database_statements.rb:235:in `block in transaction'
/usr/local/rvm/gems/ruby-2.5.0/gems/activerecord-5.1.5/lib/active_record/connection_adapters/abstract/transaction.rb:194:in `block in within_new_transaction'
/usr/local/rvm/rubies/ruby-2.5.0/lib/ruby/2.5.0/monitor.rb:226:in `mon_synchronize'
/usr/local/rvm/gems/ruby-2.5.0/gems/activerecord-5.1.5/lib/active_record/connection_adapters/abstract/transaction.rb:191:in `within_new_transaction'
/usr/local/rvm/gems/ruby-2.5.0/gems/activerecord-5.1.5/lib/active_record/connection_adapters/abstract/database_statements.rb:235:in `transaction'
/usr/local/rvm/gems/ruby-2.5.0/gems/activerecord-5.1.5/lib/active_record/transactions.rb:210:in `transaction'
/usr/local/rvm/gems/ruby-2.5.0/gems/activerecord-5.1.5/lib/active_record/transactions.rb:381:in `with_transaction_returning_status'
/usr/local/rvm/gems/ruby-2.5.0/gems/activerecord-5.1.5/lib/active_record/transactions.rb:308:in `block in save'
/usr/local/rvm/gems/ruby-2.5.0/gems/activerecord-5.1.5/lib/active_record/transactions.rb:323:in `rollback_active_record_state!'
/usr/local/rvm/gems/ruby-2.5.0/gems/activerecord-5.1.5/lib/active_record/transactions.rb:307:in `save'
/usr/local/rvm/gems/ruby-2.5.0/gems/activerecord-5.1.5/lib/active_record/suppressor.rb:42:in `save'
/home/ubuntu/workspace/web_monitor/lib/tasks/scheduler.rake:19:in `block (2 levels) in <top (required)>'
/usr/local/rvm/gems/ruby-2.5.0/gems/activerecord-5.1.5/lib/active_record/relation/delegation.rb:39:in `each'
/usr/local/rvm/gems/ruby-2.5.0/gems/activerecord-5.1.5/lib/active_record/relation/delegation.rb:39:in `each'
/home/ubuntu/workspace/web_monitor/lib/tasks/scheduler.rake:5:in `block in <top (required)>'
/usr/local/rvm/rubies/ruby-2.5.0/lib/ruby/gems/2.5.0/gems/rake-12.3.0/lib/rake/task.rb:251:in `block in execute'
/usr/local/rvm/rubies/ruby-2.5.0/lib/ruby/gems/2.5.0/gems/rake-12.3.0/lib/rake/task.rb:251:in `each'
/usr/local/rvm/rubies/ruby-2.5.0/lib/ruby/gems/2.5.0/gems/rake-12.3.0/lib/rake/task.rb:251:in `execute'
/usr/local/rvm/rubies/ruby-2.5.0/lib/ruby/gems/2.5.0/gems/rake-12.3.0/lib/rake/task.rb:195:in `block in invoke_with_call_chain'
/usr/local/rvm/rubies/ruby-2.5.0/lib/ruby/2.5.0/monitor.rb:226:in `mon_synchronize'
/usr/local/rvm/rubies/ruby-2.5.0/lib/ruby/gems/2.5.0/gems/rake-12.3.0/lib/rake/task.rb:188:in `invoke_with_call_chain'
/usr/local/rvm/rubies/ruby-2.5.0/lib/ruby/gems/2.5.0/gems/rake-12.3.0/lib/rake/task.rb:181:in `invoke'
/usr/local/rvm/rubies/ruby-2.5.0/lib/ruby/gems/2.5.0/gems/rake-12.3.0/lib/rake/application.rb:160:in `invoke_task'
/usr/local/rvm/rubies/ruby-2.5.0/lib/ruby/gems/2.5.0/gems/rake-12.3.0/lib/rake/application.rb:116:in `block (2 levels) in top_level'
/usr/local/rvm/rubies/ruby-2.5.0/lib/ruby/gems/2.5.0/gems/rake-12.3.0/lib/rake/application.rb:116:in `each'
/usr/local/rvm/rubies/ruby-2.5.0/lib/ruby/gems/2.5.0/gems/rake-12.3.0/lib/rake/application.rb:116:in `block in top_level'
/usr/local/rvm/rubies/ruby-2.5.0/lib/ruby/gems/2.5.0/gems/rake-12.3.0/lib/rake/application.rb:125:in `run_with_threads'
/usr/local/rvm/rubies/ruby-2.5.0/lib/ruby/gems/2.5.0/gems/rake-12.3.0/lib/rake/application.rb:110:in `top_level'
/usr/local/rvm/rubies/ruby-2.5.0/lib/ruby/gems/2.5.0/gems/rake-12.3.0/lib/rake/application.rb:83:in `block in run'
/usr/local/rvm/rubies/ruby-2.5.0/lib/ruby/gems/2.5.0/gems/rake-12.3.0/lib/rake/application.rb:186:in `standard_exception_handling'
/usr/local/rvm/rubies/ruby-2.5.0/lib/ruby/gems/2.5.0/gems/rake-12.3.0/lib/rake/application.rb:80:in `run'
/usr/local/rvm/gems/ruby-2.5.0@global/gems/rake-12.3.0/exe/rake:27:in `<top (required)>'
/usr/local/rvm/rubies/ruby-2.5.0/bin/rake:29:in `load'
/usr/local/rvm/rubies/ruby-2.5.0/bin/rake:29:in `<main>'
Tasks: TOP => crawl_next

lib/tasks/scheduler.rake：

desc "perform crawls for active alerts if their interval has passed"
task :crawl_next => :environment do
  alerts = Alert.where(active: true).includes(:crawls)

  alerts.each do |alert|
    last = alert.crawls.last

    last_crawl_time = last.crawl_time if !last.nil?

    if last.nil? ||
       (last_crawl_time + alert.crawl_interval_mins*60) < Time.now + 1
      crawl_stats = alert.crawl
    end

    if crawl_stats
      crawl = Crawl.new(crawl_stats)
      crawl.save

      if crawl.exceeds_limits? || crawl.errors
        UserMailer.crawl_alert(alert, crawl).deliver_later
      end
    else
      alert.deactivate
    end
  end
end

crawl.rb 模型：

class Crawl < ActiveRecord::Base
  belongs_to :alert

  after_save :update_alert_last_crawl

  def update_alert_last_crawl
    alert = self.alert
    alert.update(last_crawl: self.crawl_time)
  end

  def exceeds_limits?
    self.resp_time_ms > self.alert.response_time_threshold_ms
  end

  def errors
    self.resp_code != "200"
  end
end

alert.rb 模型：

class Alert < ActiveRecord::Base
  has_many :user_alerts
  has_many :users, through: :user_alerts, dependent: :destroy
  has_many :crawls, dependent: :destroy

  before_save :activate # TODO: don't activate all alerts before save

  validate :valid_url? # Using custom method instead of valid url gem

  validates :crawl_interval_mins, presence: true, inclusion: {in: [10, 30, 60]}
  validates :notify_emails, presence: true, length: {minimum: 6}
  validates :name, presence: true, length: {minimum: 2}

  def activate
    self.active = true
  end

  def deactivate
    self.active = false
    UserMailer.alert_deactivated(self).deliver_later
  end

  # Return a hash corresponding to a Crawl's schema, to be used in creating
  # a new crawl record
  def crawl
    data = {}
    resp = nil

    time = Benchmark.measure do
      begin
        resp = HTTParty.get(self.url)
      rescue => e
        data = crawl_error_info(e)
      end
    end

    {
      alert_id: self.id,
      crawl_time: Time.now.to_s,
      resp_code: data[:resp_code] || resp.code,
      resp_time_ms: data[:resp_time_ms] || time.real * 1_000,
      resp_status: data[:resp_status] || resp.message,
      resp_size_kb: data[:resp_size_kb] || resp.size # TODO: convert to mb
    }
  end

  def valid_url?
    if !self.url.match(/^(((http|https):\/\/|)?[a-z0-9]+([\-\.]{1}[a-z0-9]+)*\.[a-z]{2,6}(:[0-9]{1,5})?(\/.*)?)$/i)
      errors.add(:url, "not valid")
    end
  end

  def crawl_error_info(e)
    if e.class == SocketError
      return {
        resp_code: 443,
        resp_time_ms: 0,
        resp_status: "NAME/SVC NOT KNOWN",
        resp_size_kb: 0 # TODO: convert to mb
      }
    end
  end
end

Answer 1

这样不好……

  def errors
    self.resp_code != "200"
  end

errors 是ActiveRecord::Base 提供的一个方法，你已经用只返回true 或false 的on 方法覆盖了它。当 Rails 尝试使用 errors.clear 清除错误时，它不会期望返回布尔值 false 并且布尔值 false 不支持 #clear。

将 errors 方法的名称更改为其他名称，例如 bad_response_code?，然后将 rake 文件中的行更改为...

if crawl.exceeds_limits? || crawl.bad_response_code?

Answer 2

在 crawl_next 任务中发生错误，在这一行：

crawl.save

然后就像你提到的，它在错误中的活动模型验证中失败了，在 errors.clear 中：

def valid?(context = nil)
  current_context, self.validation_context = validation_context, context
  errors.clear
  run_validations!
ensure
  self.validation_context = current_context
end

在 Crawl 保存之前进行撬动，以查看哪些数据正在传递到 Crawl.new 以解决问题。