Class: Delayed::Job

Inherits:
ActiveRecord::Base
  • Object
show all
Defined in:
lib/delayed/job.rb

Overview

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

Constant Summary collapse

MAX_ATTEMPTS = 
25
MAX_RUN_TIME = 
4.hours
NextTaskSQL = 
'completed = ? AND (run_at <= ? AND (locked_at IS NULL OR locked_at < ?) OR (locked_by = ?)) AND failed_at IS NULL'
NextTaskOrder = 
'priority DESC, run_at ASC'
ParseObjectFromYaml = 
/\!ruby\/\w+\:([^\s]+)/

Class Method Summary collapse

Instance Method Summary collapse

Class Method Details

.clear_locks! ⇒ Object

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



38
39
40
 
# File 'lib/delayed/job.rb', line 38

def self.clear_locks!
  update_all("locked_by = null, locked_at = null", ["locked_by = ?", worker_name])
end

.enqueue(*args, &block) ⇒ Object

Add a job to the queue



114
115
116
117
118
119
120
121
122
123
124
125
 
# File 'lib/delayed/job.rb', line 114

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.first || 0
  run_at   = args[1]

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

.enqueue_for(owned_by, *args, &block) ⇒ Object 



127
128
129
130
131
132
133
134
135
136
137
 
# File 'lib/delayed/job.rb', line 127

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

  owner_key = self.owner_key_for(owned_by)

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

  Job.create!(:payload_object => object, :priority => priority.to_i, :run_at => run_at,
             :owner => owner_key)
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). Return in random order prevent everyone trying to do same head job at once.



153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
 
# File 'lib/delayed/job.rb', line 153

def self.find_available(limit = 5, max_run_time = MAX_RUN_TIME)

  time_now = db_time_now

  sql = NextTaskSQL.dup

  conditions = [false, time_now, time_now - max_run_time, worker_name]

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

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

  conditions.unshift(sql)

  records = ActiveRecord::Base.silence do
    find(:all, :conditions => conditions, :order => NextTaskOrder, :limit => limit)
  end

  records.sort_by { rand() }
end

.owner_key_for(owned_by) ⇒ Object 



139
140
141
142
143
144
145
146
147
148
149
 
# File 'lib/delayed/job.rb', line 139

def self.owner_key_for(owned_by)
  case owned_by
  when String
    owned_by
  when ActiveRecord::Base
    raise(ArgumentError, 'Owner cannot be a new_record') if owned_by.new_record?
    "#{owned_by.class}_#{owned_by.id}"
  else
    raise ArgumentError, 'Only strings and descendants of ActiveRecord::Base are allowed'
  end
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



182
183
184
185
186
187
188
189
190
191
192
 
# File 'lib/delayed/job.rb', line 182

def self.reserve_and_run_one_job(max_run_time = MAX_RUN_TIME)

  # We get up to 5 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(5, 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 5 were not lockable
end

.work_off(num = 100) ⇒ Object

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



229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
 
# File 'lib/delayed/job.rb', line 229

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:

  • (Boolean) 


42
43
44
 
# File 'lib/delayed/job.rb', line 42

def failed?
  failed_at
end

#invoke_job ⇒ Object

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



248
249
250
251
252
253
254
255
256
 
# File 'lib/delayed/job.rb', line 248

def invoke_job
  res = payload_object.perform

  if res.respond_to? :to_yaml
    self.result = res.to_yaml
  else
    logger.info "* [JOB] res does not respond to #to_yaml"
  end
end

#lock_exclusively!(max_run_time, worker = worker_name) ⇒ Object

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



196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
 
# File 'lib/delayed/job.rb', line 196

def lock_exclusively!(max_run_time, worker = worker_name)
  now = self.class.db_time_now
  affected_rows = if locked_by != worker
    # 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], ["id = ? and (locked_at is null or locked_at < ?)", id, (now - max_run_time.to_i)])
  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])
  end
  if affected_rows == 1
    self.locked_at    = now
    self.locked_by    = worker
    return true
  else
    return false
  end
end

#log_exception(error) ⇒ Object

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



222
223
224
225
 
# File 'lib/delayed/job.rb', line 222

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

#name ⇒ Object 



51
52
53
54
55
56
57
58
59
60
 
# File 'lib/delayed/job.rb', line 51

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 



47
48
49
 
# File 'lib/delayed/job.rb', line 47

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

#payload_object=(object) ⇒ Object 



62
63
64
 
# File 'lib/delayed/job.rb', line 62

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

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

Reschedule the job in the future (when a job fails). Uses an exponential scale depending on the number of failed attempts.



68
69
70
71
72
73
74
75
76
77
78
79
80
81
 
# File 'lib/delayed/job.rb', line 68

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

    self.attempts    += 1
    self.run_at       = time
    self.last_error   = message + "\n" + backtrace.join("\n")
    self.unlock
    save!
  else
    logger.info "* [JOB] PERMANENTLY removing #{self.name} because of #{attempts} consequetive failures."
    destroy_failed_jobs ? destroy : update_attribute(:failed_at, Time.now)
  end
end

#run_with_lock(max_run_time, worker_name) ⇒ Object

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



85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
 
# File 'lib/delayed/job.rb', line 85

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

  begin
    runtime =  Benchmark.realtime do
      invoke_job # TODO: raise error if takes longer than max_run_time
      if destroy_completed_jobs
        destroy
      else
        self.completed = true
        save
      end
    end
    # TODO: warn if runtime > max_run_time ?
    logger.info "* [JOB] #{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

#unlock ⇒ Object

Unlock this job (note: not saved to DB)



216
217
218
219
 
# File 'lib/delayed/job.rb', line 216

def unlock
  self.locked_at    = nil
  self.locked_by    = nil
end