Class: Delayed::Job

Inherits:
ActiveRecord::Base
  • Object
show all
Extended by:
JobDeprecations
Defined in:
lib/delayed_on_steroids/job.rb

Overview

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

Constant Summary collapse

MAX_ATTEMPTS = 
25
MAX_RUN_TIME = 
4.hours
ParseObjectFromYaml = 
/\!ruby\/\w+\:([^\s]+)/

Class Method Summary collapse

Instance Method Summary collapse

Methods included from JobDeprecations

move_methods_to_worker

Class Method Details

.db_time_now ⇒ Object

Get the current time (GMT or local depending on DB) Note: This does not ping the DB to get the time, so all your clients must have syncronized clocks.



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# File 'lib/delayed_on_steroids/job.rb', line 222

def self.db_time_now
  if Time.zone
    Time.zone.now
  elsif ActiveRecord::Base.default_timezone == :utc
    Time.now.utc
  else
    Time.now
  end
end

.enqueue(*args, &block) ⇒ Object

Add a job to the queue. Arguments: priority, run_at.



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# File 'lib/delayed_on_steroids/job.rb', line 95

def self.enqueue(*args, &block)
  object = block_given? ? EvaledJob.new(&block) : args.shift

  unless object.respond_to?(:perform) || block_given?
    raise ArgumentError, 'Cannot enqueue items which do not respond to perform'
  end

  priority = args[0] || 0
  run_at   = args[1]

  Job.create(:payload_object => object, :priority => priority.to_i, :run_at => run_at)
end

.find_available(limit = 5, max_run_time = MAX_RUN_TIME) ⇒ Object

Find a few candidate jobs to run (in case some immediately get locked by others).



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# File 'lib/delayed_on_steroids/job.rb', line 109

def self.find_available(limit = 5, max_run_time = MAX_RUN_TIME)
  time_now = db_time_now
  sql = ''
  conditions = []

  # 1) not scheduled in the future
  sql << '(run_at <= ?)'
  conditions << time_now

  # 2) and job is not failed yet
  sql << ' AND (failed_at IS NULL)'

  # 3a) and already locked by same worker
  sql << ' AND ('
  sql << '(locked_by = ?)'
  conditions << Worker.name

  # 3b) or not locked yet
  sql << ' OR (locked_at IS NULL)'

  # 3c) or lock expired
  sql << ' OR (locked_at < ?)'
  sql << ')'
  conditions << time_now - max_run_time

  if Worker.min_priority
    sql << ' AND (priority >= ?)'
    conditions << Worker.min_priority
  end

  if Worker.max_priority
    sql << ' AND (priority <= ?)'
    conditions << Worker.max_priority
  end

  if Worker.job_types
    sql << ' AND (job_type IN (?))'
    conditions << Worker.job_types
  end

  conditions.unshift(sql)
  find(:all, :conditions => conditions, :order => 'priority ASC, run_at ASC', :limit => limit)
end

.reserve_and_run_one_job(max_run_time = MAX_RUN_TIME) ⇒ Object

Run the next job we can get an exclusive lock on. If no jobs are left we return nil



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# File 'lib/delayed_on_steroids/job.rb', line 155

def self.reserve_and_run_one_job(max_run_time = MAX_RUN_TIME)

  # We get up to 20 jobs from the db. In case we cannot get exclusive access to a job we try the next.
  # this leads to a more even distribution of jobs across the worker processes
  find_available(20, max_run_time).each do |job|
    t = job.run_with_lock(max_run_time, Worker.name)
    return t unless t == nil  # return if we did work (good or bad)
  end

  nil # we didn't do any work, all 20 were not lockable
end

.work_off(num = 100) ⇒ Object

Do num jobs and return stats on success/failure. Exit early if interrupted.



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# File 'lib/delayed_on_steroids/job.rb', line 196

def self.work_off(num = 100)
  success, failure = 0, 0

  num.times do
    case self.reserve_and_run_one_job
    when true
        success += 1
    when false
        failure += 1
    else
      break  # leave if no work could be done
    end
    break if $exit # leave if we're exiting
  end

  return [success, failure]
end

Instance Method Details

#failed? ⇒ Boolean Also known as: failed

Returns true if current job failed.

Returns:

  • (Boolean) 


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# File 'lib/delayed_on_steroids/job.rb', line 22

def failed?
  not failed_at.nil?
end

#invoke_job ⇒ Object

Moved into its own method so that new_relic can trace it.



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# File 'lib/delayed_on_steroids/job.rb', line 215

def invoke_job
  payload_object.perform
end

#lock_exclusively!(max_run_time = MAX_RUN_TIME, worker_name = Worker.name) ⇒ Object

Lock this job for this worker. Returns true if we have the lock, false otherwise.



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# File 'lib/delayed_on_steroids/job.rb', line 169

def lock_exclusively!(max_run_time = MAX_RUN_TIME, worker_name = Worker.name)
  now = self.class.db_time_now
  affected_rows = if locked_by != worker_name
    # We don't own this job so we will update the locked_by name and the locked_at
    self.class.update_all(["locked_at = ?, locked_by = ?", now, worker_name], ["id = ? and (locked_at is null or locked_at < ?) and (run_at <= ?)", id, (now - max_run_time.to_i), now])
  else
    # We already own this job, this may happen if the job queue crashes.
    # Simply resume and update the locked_at
    self.class.update_all(["locked_at = ?", now], ["id = ? and locked_by = ?", id, worker_name])
  end
  if affected_rows == 1
    self.locked_at    = now
    self.locked_by    = worker_name
    return true
  else
    return false
  end
end

#locked? ⇒ Boolean Also known as: locked

Returns true if current job locked.

Returns:

  • (Boolean) 


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# File 'lib/delayed_on_steroids/job.rb', line 28

def locked?
  not locked_at.nil?
end

#log_exception(e) ⇒ Object

This is a good hook if you need to report job processing errors in additional or different ways



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# File 'lib/delayed_on_steroids/job.rb', line 189

def log_exception(e)
  Worker.logger.error("! [#{Worker.name}] #{name} failed with #{e.class.name}: #{e.message} - #{attempts} failed attempts")
  Worker.logger.error(e)
end

#name ⇒ Object

Returns job name.



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# File 'lib/delayed_on_steroids/job.rb', line 43

def name
  @name ||= begin
    payload = payload_object
    if payload.respond_to?(:display_name)
      payload.display_name
    else
      payload.class.name
    end
  end
end

#payload_object ⇒ Object 



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# File 'lib/delayed_on_steroids/job.rb', line 33

def payload_object
  @payload_object ||= deserialize(self['handler'])
end

#payload_object=(object) ⇒ Object 



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# File 'lib/delayed_on_steroids/job.rb', line 37

def payload_object=(object)
  self['job_type'] = object.class.to_s
  self['handler']  = object.to_yaml
end

#reschedule(message, backtrace = [], time = nil) ⇒ Object

Reschedule the job to run at time (when a job fails). If time is nil it uses an exponential scale depending on the number of failed attempts.



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# File 'lib/delayed_on_steroids/job.rb', line 56

def reschedule(message, backtrace = [], time = nil)
  if (self.attempts += 1) < MAX_ATTEMPTS
    time ||= Job.db_time_now + (attempts ** 4) + 5

    self.run_at       = time
    self.last_error   = message + "\n" + backtrace.join("\n")
    self.locked_at    = nil
    self.locked_by    = nil
    save!
  else
    Worker.logger.warn("* [#{Worker.name}] PERMANENTLY removing #{self.name} because of #{attempts} consequetive failures.")
    Worker.destroy_failed_jobs ? destroy : update_attribute(:failed_at, self.class.db_time_now)
  end
end

#run_with_lock(max_run_time = MAX_RUN_TIME, worker_name = Worker.name) ⇒ Object

Try to run one job. Returns true/false (work done/work failed) or nil if job can’t be locked.



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# File 'lib/delayed_on_steroids/job.rb', line 72

def run_with_lock(max_run_time = MAX_RUN_TIME, worker_name = Worker.name)
  Worker.logger.info("* [#{Worker.name}] acquiring lock on #{name}")
  unless lock_exclusively!(max_run_time, worker_name)
    # We did not get the lock, some other worker process must have
    Worker.logger.warn("* [#{Worker.name}] failed to acquire exclusive lock for #{name}")
    return nil # no work done
  end

  begin
    runtime =  Benchmark.realtime do
      Timeout.timeout(max_run_time.to_i) { invoke_job }
      destroy
    end
    Worker.logger.info("* [#{Worker.name}] #{name} completed after %.4f" % runtime)
    return true  # did work
  rescue Exception => e
    reschedule(e.message, e.backtrace)
    log_exception(e)
    return false  # work failed
  end
end