Class: Delayed::Job

Inherits:
Object
  • Object
show all
Includes:
DataMapper::Resource
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

4 * 3600
NextTaskSQL = 
'(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.



71
72
73
74
 
# File 'lib/delayed/job.rb', line 71

def self.clear_locks!
#      update_all("locked_by = null, locked_at = null", ["locked_by = ?", worker_name])
  Job.all( :locked_by => worker_name ).update( :locked_by => nil , :locked_at => nil )
end

.enqueue(*args, &block) ⇒ Object

Add a job to the queue



143
144
145
146
147
148
149
150
151
152
153
154
 
# File 'lib/delayed/job.rb', line 143

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] || DateTime.new(0)

  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). Return in random order prevent everyone trying to do same head job at once.



158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
 
# File 'lib/delayed/job.rb', line 158

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

  time_now = Time.now

  sql = NextTaskSQL.dup
  conditions = [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 = all( :conditions => conditions, :order => NextTaskOrder, :limit => limit )
  #records.sort_by { rand() }
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



183
184
185
186
187
188
189
190
191
192
193
 
# File 'lib/delayed/job.rb', line 183

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.



233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
 
# File 'lib/delayed/job.rb', line 233

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) 


76
77
78
 
# File 'lib/delayed/job.rb', line 76

def failed?
  failed_at
end

#invoke_job ⇒ Object

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



252
253
254
 
# File 'lib/delayed/job.rb', line 252

def invoke_job
  payload_object.perform
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.



197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
 
# File 'lib/delayed/job.rb', line 197

def lock_exclusively!(max_run_time, worker = worker_name)
  now = Time.now
  updated = 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)])
    Job.all( :conditions => ["id = ? AND (locked_at IS null OR locked_at < ?)", id, (now - max_run_time.to_i)] ).update( :locked_at => now , :locked_by => worker )
  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])
    Job.all( :id => id , :locked_by => worker ).update( :locked_at => now )
  end
  p "Lock updated? ", updated
  if updated
    locked_at    = now
    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



226
227
228
229
 
# File 'lib/delayed/job.rb', line 226

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

#name ⇒ Object 



85
86
87
88
89
90
91
92
93
94
 
# File 'lib/delayed/job.rb', line 85

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 



81
82
83
 
# File 'lib/delayed/job.rb', line 81

def payload_object
  @payload_object ||= deserialize( handler )
end

#payload_object=(object) ⇒ Object 



96
97
98
 
# File 'lib/delayed/job.rb', line 96

def payload_object=(object)
  attribute_set( :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.



102
103
104
105
106
107
108
109
110
111
112
113
114
115
 
# File 'lib/delayed/job.rb', line 102

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

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



119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
 
# File 'lib/delayed/job.rb', line 119

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
      destroy
    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)



220
221
222
223
 
# File 'lib/delayed/job.rb', line 220

def unlock
  locked_at    = nil
  locked_by    = nil
end