NoMethodError when attempting ActiveRecord save in database in Rails app

Question

The app I'm building is a very simple website monitoring tool with Users, Alerts, and Crawls. I created a Rake task to take care of crawling the sites at specified intervals, and it was working fine, saving the crawl history to the db when manually run with rake crawl_next.

After integrating logic to check if the crawl is over a user's specified limits or there are errors & then emailing the user, I'm no longer able to save a crawl record to the database. I'm getting a NoMethodError: undefined method 'clear' for false:FalseClass when running the rake task, which I can't pinpoint the source of. Based on the console output, I presume it's some failing validation, but I can't determine what validation might be causing it to fail. I'm hoping a more experienced Dev can point me in the right direction.

I've isolated the issue with the saving of the crawl record to the database...I think.

• I've used pry to inspect the inputs & variables, and nothing seems amiss.
• I've commented out the after_save action on the crawl model to eliminate possible alert model code errors.
• In the Rails console, I've tried manually creating new crawls using both mass assignment & the .create method. It fails the same way.
• Using Rails 5.1.5 w/ Ruby 2.5.0p0, c9.io IDE

Console output:

** 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 model:

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 model:

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

This is not good...

  def errors
    self.resp_code != "200"
  end

errors is a method provided by ActiveRecord::Base and you've overwritten it with your on method that just returns true or false. When Rails tries to clear down errors using errors.clear it's not expecting to get back a boolean false and the boolean false doesn't support #clear.

Change the name of your errors method to something else, like maybe bad_response_code? and then change the line in your rake file to...

if crawl.exceeds_limits? || crawl.bad_response_code?

Answer 2

The error is happening in the crawl_next task, in this line:

crawl.save

Then like you mentioned it is failing in the active model validations in this method, in errors.clear:

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

Put a pry before the Crawl save to see what data is being passed into the Crawl.new to clear the issue.