Class: Delayed::Backend::ActiveRecord::Job

Inherits:
ActiveRecord::Base
  • Object
show all
Includes:
Base
Defined in:
lib/delayed/backend/active_record.rb

Overview

A job object that is persisted to the database. Contains the work object as a YAML field.

Direct Known Subclasses

Failed

Defined Under Namespace

Classes: Failed

Constant Summary

Constants included from Base

Base::ON_HOLD_COUNT, Base::ON_HOLD_LOCKED_BY

Class Method Summary collapse

Instance Method Summary collapse

Methods included from Base

#batch?, #expired?, #failed?, #full_name, #hold!, included, #initialize_defaults, #invoke_job, #locked?, #name, #on_hold?, #payload_object, #payload_object=, #permanent_failure, #reschedule, #reschedule_at, #unhold!, #unlock

Class Method Details

.all_available(queue = Delayed::Settings.queue, min_priority = nil, max_priority = nil, forced_latency: nil) ⇒ Object 



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# File 'lib/delayed/backend/active_record.rb', line 360

def self.all_available(queue = Delayed::Settings.queue,
                       min_priority = nil,
                       max_priority = nil,
                       forced_latency: nil)
  min_priority ||= Delayed::MIN_PRIORITY
  max_priority ||= Delayed::MAX_PRIORITY

  check_queue(queue)
  check_priorities(min_priority, max_priority)

  self.ready_to_run(forced_latency: forced_latency).
      where(:priority => min_priority..max_priority, :queue => queue).
      by_priority
end

.bulk_update(action, opts) ⇒ Object

perform a bulk update of a set of jobs action is :hold, :unhold, or :destroy to specify the jobs to act on, either pass opts = [list of job ids] or opts = <some flavor> to perform on all jobs of that flavor



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# File 'lib/delayed/backend/active_record.rb', line 204

def self.bulk_update(action, opts)
  raise("Can't #{action.to_s} failed jobs") if opts[:flavor].to_s == 'failed' && action.to_s != 'destroy'
  scope = if opts[:ids]
    if opts[:flavor] == 'failed'
      Delayed::Job::Failed.where(:id => opts[:ids])
    else
      self.where(:id => opts[:ids])
    end
  elsif opts[:flavor]

    self.scope_for_flavor(opts[:flavor], opts[:query])
  end

  return 0 unless scope

  case action.to_s
  when 'hold'
    scope = scope.where(locked_by: nil)
    scope.update_all(:locked_by => ON_HOLD_LOCKED_BY, :locked_at => db_time_now, :attempts => ON_HOLD_COUNT)
  when 'unhold'
    now = db_time_now
    scope = scope.where(locked_by: ON_HOLD_LOCKED_BY)
    scope.update_all(["locked_by = NULL, locked_at = NULL, attempts = 0, run_at = (CASE WHEN run_at > ? THEN run_at ELSE ? END), failed_at = NULL", now, now])
  when 'destroy'
    scope = scope.where("locked_by IS NULL OR locked_by=?", ON_HOLD_LOCKED_BY) unless opts[:flavor] == 'failed'
    scope.delete_all
  end
end

.by_priority ⇒ Object 



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# File 'lib/delayed/backend/active_record.rb', line 135

def self.by_priority
  order(:priority, :run_at, :id)
end

.clear_locks!(worker_name) ⇒ Object

When a worker is exiting, make sure we don’t have any locked jobs.



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# File 'lib/delayed/backend/active_record.rb', line 140

def self.clear_locks!(worker_name)
  where(:locked_by => worker_name).update_all(:locked_by => nil, :locked_at => nil)
end

.create(attributes, &block) ⇒ Object 



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# File 'lib/delayed/backend/active_record.rb', line 25

def create(attributes, &block)
  return super if connection.prepared_statements || Rails.version < '5.2'

  # modified from ActiveRecord::Persistence.create and ActiveRecord::Persistence#_insert_record
  job = new(attributes, &block)
  job.single_step_create
end

.create_singleton(options) ⇒ Object

Create the job on the specified strand, but only if there aren’t any other non-running jobs on that strand. (in other words, the job will still be created if there’s another job on the strand but it’s already running)



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# File 'lib/delayed/backend/active_record.rb', line 397

def self.create_singleton(options)
  strand = options[:strand]
  on_conflict = options.delete(:on_conflict) || :use_earliest
  transaction_for_singleton(strand, on_conflict) do
    job = self.where(:strand => strand, :locked_at => nil).order(:id).first
    new_job = new(options)
    if job
      new_job.initialize_defaults
      job.run_at =
        case on_conflict
        when :use_earliest, :patient
          [job.run_at, new_job.run_at].min
        when :overwrite
          new_job.run_at
        when :loose
          job.run_at
        end
      job.handler = new_job.handler if on_conflict == :overwrite
      job.save! if job.changed?
    else
      new_job.save!
    end
    job || new_job
  end
end

.current ⇒ Object 



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# File 'lib/delayed/backend/active_record.rb', line 109

def self.current
  where("run_at<=?", db_time_now)
end

.failed ⇒ Object 



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# File 'lib/delayed/backend/active_record.rb', line 117

def self.failed
  where("failed_at IS NOT NULL")
end

.find_available(limit, queue = Delayed::Settings.queue, min_priority = nil, max_priority = nil) ⇒ Object 



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# File 'lib/delayed/backend/active_record.rb', line 353

def self.find_available(limit,
                        queue = Delayed::Settings.queue,
                        min_priority = nil,
                        max_priority = nil)
  all_available(queue, min_priority, max_priority).limit(limit).to_a
end

.future ⇒ Object 



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# File 'lib/delayed/backend/active_record.rb', line 113

def self.future
  where("run_at>?", db_time_now)
end

.get_and_lock_next_available(worker_names, queue = Delayed::Settings.queue, min_priority = nil, max_priority = nil, prefetch: 0, prefetch_owner: nil, forced_latency: nil) ⇒ Object 



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# File 'lib/delayed/backend/active_record.rb', line 259

def self.get_and_lock_next_available(worker_names,
                                     queue = Delayed::Settings.queue,
                                     min_priority = nil,
                                     max_priority = nil,
                                     prefetch: 0,
                                     prefetch_owner: nil,
                                     forced_latency: nil)

  check_queue(queue)
  check_priorities(min_priority, max_priority)

  loop do
    jobs = maybe_silence_periodic_log do
      if connection.adapter_name == 'PostgreSQL' && !Settings.select_random_from_batch
        # In Postgres, we can lock a job and return which row was locked in a single
        # query by using RETURNING. Combine that with the ROW_NUMBER() window function
        # to assign a distinct locked_at value to each job locked, when doing multiple
        # jobs in a single query.
        effective_worker_names = Array(worker_names)

        lock = nil
        lock = "FOR UPDATE SKIP LOCKED" if connection.postgresql_version >= 90500
        target_jobs = all_available(queue,
                                    min_priority,
                                    max_priority,
                                    forced_latency: forced_latency).
            limit(effective_worker_names.length + prefetch).
            lock(lock)
        jobs_with_row_number = all.from(target_jobs).
            select("id, ROW_NUMBER() OVER () AS row_number")
        updates = "locked_by = CASE row_number "
        effective_worker_names.each_with_index do |worker, i|
          updates << "WHEN #{i + 1} THEN #{connection.quote(worker)} "
        end
        if prefetch_owner
          updates << "ELSE #{connection.quote(prefetch_owner)} "
        end
        updates << "END, locked_at = #{connection.quote(db_time_now)}"

        # Originally this was done with a subquery, but this allows the query planner to
        # side-step the LIMIT. We use a CTE here to force the subquery to be materialized
        # before running the UPDATE.
        #
        # For more details, see:
        #  * https://dba.stackexchange.com/a/69497/55285
        #  * https://github.com/feikesteenbergen/demos/blob/b7ecee8b2a79bf04cbcd74972e6bfb81903aee5d/bugs/update_limit_bug.txt
        query = "WITH limited_jobs AS (#{jobs_with_row_number.to_sql}) " \
                "UPDATE #{quoted_table_name} SET #{updates} FROM limited_jobs WHERE limited_jobs.id=#{quoted_table_name}.id " \
                "RETURNING #{quoted_table_name}.*"

        jobs = find_by_sql(query)
        # because this is an atomic query, we don't have to return more jobs than we needed
        # to try and lock them, nor is there a possibility we need to try again because
        # all of the jobs we tried to lock had already been locked by someone else
        if worker_names.is_a?(Array)
          result = jobs.index_by(&:locked_by)
          # all of the prefetched jobs can come back as an array
          result[prefetch_owner] = jobs.select { |j| j.locked_by == prefetch_owner } if prefetch_owner
          return result
        else
          return jobs.first
        end
      else
        batch_size = Settings.fetch_batch_size
        batch_size *= worker_names.length if worker_names.is_a?(Array)
        find_available(batch_size, queue, min_priority, max_priority)
      end
    end
    if jobs.empty?
      return worker_names.is_a?(Array) ? {} : nil
    end
    if Settings.select_random_from_batch
      jobs = jobs.sort_by { rand }
    end
    if worker_names.is_a?(Array)
      result = {}
      jobs.each do |job|
        break if worker_names.empty?
        worker_name = worker_names.first
        if job.send(:lock_exclusively!, worker_name)
          result[worker_name] = job
          worker_names.shift
        end
      end
      return result
    else
      job = jobs.detect do |job|
        job.send(:lock_exclusively!, worker_names)
      end
      return job if job
    end
  end
end

.jobs_count(flavor, query = nil) ⇒ Object

get the total job count for the given flavor see list_jobs for documentation on arguments



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# File 'lib/delayed/backend/active_record.rb', line 194

def self.jobs_count(flavor,
                    query = nil)
  scope = self.scope_for_flavor(flavor, query)
  scope.count
end

.list_jobs(flavor, limit, offset = 0, query = nil) ⇒ Object

get a list of jobs of the given flavor in the given queue flavor is :current, :future, :failed, :strand or :tag depending on the flavor, query has a different meaning: for :current and :future, it’s the queue name (defaults to Delayed::Settings.queue) for :strand it’s the strand name for :tag it’s the tag name for :failed it’s ignored



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# File 'lib/delayed/backend/active_record.rb', line 183

def self.list_jobs(flavor,
                   limit,
                   offset = 0,
                   query = nil)
  scope = self.scope_for_flavor(flavor, query)
  order = flavor.to_s == 'future' ? 'run_at' : 'id desc'
  scope.order(order).limit(limit).offset(offset).to_a
end

.maybe_silence_periodic_log(&block) ⇒ Object 



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# File 'lib/delayed/backend/active_record.rb', line 251

def self.maybe_silence_periodic_log(&block)
  if Settings.silence_periodic_log
    ::ActiveRecord::Base.logger.silence(&block)
  else
    block.call
  end
end

.n_strand_options(strand_name, num_strands) ⇒ Object

This overwrites the previous behavior so rather than changing the strand and balancing at queue time, this keeps the strand intact and uses triggers to limit the number running



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# File 'lib/delayed/backend/active_record.rb', line 105

def self.n_strand_options(strand_name, num_strands)
  {:strand => strand_name, :max_concurrent => num_strands}
end

.processes_locked_locally(name: nil) ⇒ Object 



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# File 'lib/delayed/backend/active_record.rb', line 423

def self.processes_locked_locally(name: nil)
  name ||= Socket.gethostname rescue x
  where("locked_by LIKE ?", "#{name}:%").pluck(:locked_by).map{|locked_by| locked_by.split(":").last.to_i}
end

.ready_to_run(forced_latency: nil) ⇒ Object

a nice stress test: 10_000.times { |i| Kernel.send_later_enqueue_args(:system, { :strand => ‘s1’, :run_at => (24.hours.ago + (rand(24.hours.to_i))) }, “echo #i >> test1.txt”) } 500.times { |i| “ohai”.send_later_enqueue_args(:reverse, { :run_at => (12.hours.ago + (rand(24.hours.to_i))) }) } then fire up your workers you can check out strand correctness: diff test1.txt <(sort -n test1.txt)



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# File 'lib/delayed/backend/active_record.rb', line 130

def self.ready_to_run(forced_latency: nil)
  now = db_time_now
  now -= forced_latency if forced_latency
  where("run_at<=? AND locked_at IS NULL AND next_in_strand=?", now, true)
end

.reconnect! ⇒ Object 



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# File 'lib/delayed/backend/active_record.rb', line 20

def self.reconnect!
  clear_all_connections!
end

.running ⇒ Object 



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# File 'lib/delayed/backend/active_record.rb', line 121

def self.running
  where("locked_at IS NOT NULL AND locked_by<>'on hold'")
end

.running_jobs ⇒ Object 



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# File 'lib/delayed/backend/active_record.rb', line 148

def self.running_jobs()
  self.running.order(:locked_at)
end

.scope_for_flavor(flavor, query) ⇒ Object 



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# File 'lib/delayed/backend/active_record.rb', line 152

def self.scope_for_flavor(flavor, query)
  scope = case flavor.to_s
  when 'current'
    self.current
  when 'future'
    self.future
  when 'failed'
    Delayed::Job::Failed
  when 'strand'
    self.where(:strand => query)
  when 'tag'
    self.where(:tag => query)
  else
    raise ArgumentError, "invalid flavor: #{flavor.inspect}"
  end

  if %w(current future).include?(flavor.to_s)
    queue = query.presence || Delayed::Settings.queue
    scope = scope.where(:queue => queue)
  end

  scope
end

.strand_size(strand) ⇒ Object 



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# File 'lib/delayed/backend/active_record.rb', line 144

def self.strand_size(strand)
  self.where(:strand => strand).count
end

.tag_counts(flavor, limit, offset = 0) ⇒ Object

returns a list of hashes { :tag => tag_name, :count => current_count } in descending count order flavor is :current or :all

Raises:

  • (ArgumentError) 


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# File 'lib/delayed/backend/active_record.rb', line 236

def self.tag_counts(flavor,
                    limit,
                    offset = 0)
  raise(ArgumentError, "invalid flavor: #{flavor}") unless %w(current all).include?(flavor.to_s)
  scope = case flavor.to_s
    when 'current'
      self.current
    when 'all'
      self
    end

  scope = scope.group(:tag).offset(offset).limit(limit)
  scope.order(Arel.sql("COUNT(tag) DESC")).count.map { |t,c| { :tag => t, :count => c } }
end

.transaction_for_singleton(strand, on_conflict) ⇒ Object

used internally by create_singleton to take the appropriate lock depending on the db driver



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# File 'lib/delayed/backend/active_record.rb', line 377

def self.transaction_for_singleton(strand, on_conflict)
  return yield if on_conflict == :loose
  self.transaction do
    if on_conflict == :patient
      pg_function = 'pg_try_advisory_xact_lock'
      execute_method = :select_value
    else
      pg_function = 'pg_advisory_xact_lock'
      execute_method = :execute
    end
    result = connection.send(execute_method, sanitize_sql(["SELECT #{pg_function}(#{connection.quote_table_name('half_md5_as_bigint')}(?))", strand]))
    return if result == false && on_conflict == :patient
    yield
  end
end

.unlock(jobs) ⇒ Object 



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# File 'lib/delayed/backend/active_record.rb', line 433

def self.unlock(jobs)
  unlocked = where(id: jobs).update_all(locked_at: nil, locked_by: nil)
  jobs.each(&:unlock)
  unlocked
end

.unlock_orphaned_prefetched_jobs ⇒ Object 



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# File 'lib/delayed/backend/active_record.rb', line 428

def self.unlock_orphaned_prefetched_jobs
  horizon = db_time_now - Settings.parent_process[:prefetched_jobs_timeout] * 4
  where("locked_by LIKE 'prefetch:%' AND locked_at<?", horizon).update_all(locked_at: nil, locked_by: nil)
end

Instance Method Details

#create_and_lock!(worker) ⇒ Object 



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# File 'lib/delayed/backend/active_record.rb', line 483

def create_and_lock!(worker)
  raise "job already exists" unless new_record?
  self.locked_at = Delayed::Job.db_time_now
  self.locked_by = worker
  single_step_create
end

#destroy ⇒ Object 



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# File 'lib/delayed/backend/active_record.rb', line 75

def destroy
  # skip transaction and callbacks
  destroy_row
end

#fail! ⇒ Object 



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# File 'lib/delayed/backend/active_record.rb', line 490

def fail!
  attrs = self.attributes
  attrs['original_job_id'] = attrs.delete('id')
  attrs['failed_at'] ||= self.class.db_time_now
  attrs.delete('next_in_strand')
  attrs.delete('max_concurrent')
  self.class.transaction do
    failed_job = Failed.create(attrs)
    self.destroy
    failed_job
  end
rescue
  # we got an error while failing the job -- we need to at least get
  # the job out of the queue
  self.destroy
  # re-raise so the worker logs the error, at least
  raise
end

#lock_strand_on_create ⇒ Object 



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# File 'lib/delayed/backend/active_record.rb', line 96

def lock_strand_on_create
  if strand.present?
    self.class.connection.execute("SELECT pg_advisory_xact_lock(#{self.class.connection.quote_table_name('half_md5_as_bigint')}(#{self.class.connection.quote(strand)}))")
  end
end

#single_step_create ⇒ Object 



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# File 'lib/delayed/backend/active_record.rb', line 34

def single_step_create
  connection = self.class.connection
  return save if connection.prepared_statements || Rails.version < '5.2'

  # a before_save callback that we're skipping
  initialize_defaults

  current_time = current_time_from_proper_timezone

  all_timestamp_attributes_in_model.each do |column|
    if !attribute_present?(column)
      _write_attribute(column, current_time)
    end
  end

  if Rails.version >= '6'
    attribute_names = attribute_names_for_partial_writes
    attribute_names = attributes_for_create(attribute_names)
    values = attributes_with_values(attribute_names)
  else
    attribute_names = partial_writes? ? keys_for_partial_write : self.attribute_names
    values = attributes_with_values_for_create(attribute_names)
  end
  im = self.class.arel_table.compile_insert(self.class.send(:_substitute_values, values))
  sql, _binds = connection.send(:to_sql_and_binds, im, [])

  # https://www.postgresql.org/docs/9.5/libpq-exec.html
  sql = "#{sql} RETURNING id"
  # > Multiple queries sent in a single PQexec call are processed in a single transaction,
  # unless there are explicit BEGIN/COMMIT commands included in the query string to divide
  # it into multiple transactions.
  sql = "SELECT pg_advisory_xact_lock(#{connection.quote_table_name('half_md5_as_bigint')}(#{connection.quote(values['strand'])})); #{sql}" if values["strand"]
  result = connection.execute(sql, "#{self} Create")
  self.id = result.values.first.first
  result.clear
  @new_record = false
  changes_applied

  self
end

#transfer_lock!(from:, to:) ⇒ Object 



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# File 'lib/delayed/backend/active_record.rb', line 457

def transfer_lock!(from:, to:)
  now = self.class.db_time_now
  # We don't own this job so we will update the locked_by name and the locked_at
  affected_rows = self.class.where(id: self, locked_by: from).update_all(locked_at: now, locked_by: to)
  if affected_rows == 1
    mark_as_locked!(now, to)
    return true
  else
    return false
  end
end