Class: Resque::Worker

Inherits:
Object
  • Object
show all
Extended by:
Helpers
Includes:
Helpers
Defined in:
lib/resque/worker.rb

Overview

A Resque Worker processes jobs. On platforms that support fork(2), the worker will fork off a child to process each job. This ensures a clean slate when beginning the next job and cuts down on gradual memory growth as well as low level failures.

It also ensures workers are always listening to signals from you, their master, and can react accordingly.

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Methods included from Helpers

classify, constantize, decode, encode, mongo_stats, mongo_workers

Constructor Details

#initialize(*queues) ⇒ Worker

Workers should be initialized with an array of string queue names. The order is important: a Worker will check the first queue given for a job. If none is found, it will check the second queue name given. If a job is found, it will be processed. Upon completion, the Worker will again check the first queue given, and so forth. In this way the queue list passed to a Worker on startup defines the priorities of queues.

If passed a single “*”, this Worker will operate on all queues in alphabetical order. Queues can be dynamically added or removed without needing to restart workers using this method.



70
71
72
73
 
# File 'lib/resque/worker.rb', line 70

def initialize(*queues)
  @queues = queues.map { |queue| queue.to_s.strip }
  validate_queues
end

Instance Attribute Details

#cant_fork ⇒ Object

Boolean indicating whether this worker can or can not fork. Automatically set if a fork(2) fails.



21
22
23
 
# File 'lib/resque/worker.rb', line 21

def cant_fork
  @cant_fork
end

#to_s ⇒ Object Also known as: id

The string representation is the same as the id for this worker instance. Can be used with ‘Worker.find`.



451
452
453
 
# File 'lib/resque/worker.rb', line 451

def to_s
  @to_s ||= "#{hostname}:#{Process.pid}:#{@queues.join(',')}"
end

#verbose ⇒ Object

Whether the worker should log basic info to STDOUT



14
15
16
 
# File 'lib/resque/worker.rb', line 14

def verbose
  @verbose
end

#very_verbose ⇒ Object

Whether the worker should log lots of info to STDOUT



17
18
19
 
# File 'lib/resque/worker.rb', line 17

def very_verbose
  @very_verbose
end

Class Method Details

.all ⇒ Object

Returns an array of all worker objects.



26
27
28
 
# File 'lib/resque/worker.rb', line 26

def self.all
  mongo_workers.distinct(:worker).map{|worker| find(worker)}.compact
end

.attach(worker_id) ⇒ Object

Alias of ‘find`



49
50
51
 
# File 'lib/resque/worker.rb', line 49

def self.attach(worker_id)
  find(worker_id)
end

.exists?(worker_id) ⇒ Boolean

Given a string worker id, return a boolean indicating whether the worker exists

Returns:

  • (Boolean) 


55
56
57
 
# File 'lib/resque/worker.rb', line 55

def self.exists?(worker_id)
  mongo_workers.find({ :worker => worker_id.to_s}).count > 0
end

.find(worker_id) ⇒ Object

Returns a single worker object. Accepts a string id.



37
38
39
40
41
42
43
44
45
46
 
# File 'lib/resque/worker.rb', line 37

def self.find(worker_id)
  if exists? worker_id
    queues = worker_id.split(':')[-1].split(',')
    worker = new(*queues)
    worker.to_s = worker_id
    worker
  else
    nil
  end
end

.working ⇒ Object

Returns an array of all worker objects currently processing jobs.



32
33
34
 
# File 'lib/resque/worker.rb', line 32

def self.working
  working = mongo_workers.find({ 'working_on' => { '$exists' => true}}).to_a.map{|w| find(w['worker'])}
end

Instance Method Details

#==(other) ⇒ Object

Is this worker the same as another worker?



441
442
443
 
# File 'lib/resque/worker.rb', line 441

def ==(other)
  to_s == other.to_s
end

#done_working ⇒ Object

Called when we are done working - clears our ‘working_on` state and tells Mongo we processed a job.



379
380
381
382
 
# File 'lib/resque/worker.rb', line 379

def done_working
  processed!
  mongo_workers.remove({ :worker => self.to_s})
end

#enable_gc_optimizations ⇒ Object

Enables GC Optimizations if you’re running REE. www.rubyenterpriseedition.com/faq.html#adapt_apps_for_cow



229
230
231
232
233
 
# File 'lib/resque/worker.rb', line 229

def enable_gc_optimizations
  if GC.respond_to?(:copy_on_write_friendly=)
    GC.copy_on_write_friendly = true
  end
end

#failed ⇒ Object

How many failed jobs has this worker seen? Returns an int.



396
397
398
 
# File 'lib/resque/worker.rb', line 396

def failed
  Stat["failed:#{self}"]
end

#failed! ⇒ Object

Tells Mongo we’ve failed a job.



401
402
403
404
 
# File 'lib/resque/worker.rb', line 401

def failed!
  Stat << "failed"
  Stat << "failed:#{self}"
end

#fork ⇒ Object

Not every platform supports fork. Here we do our magic to determine if yours does.



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

def fork
  @cant_fork = true if $TESTING

  return if @cant_fork

  begin
    # IronRuby doesn't support `Kernel.fork` yet
    if Kernel.respond_to?(:fork)
      Kernel.fork
    else
      raise NotImplementedError
    end
  rescue NotImplementedError
    @cant_fork = true
    nil
  end
end

#hostname ⇒ Object

chomp’d hostname of this machine



457
458
459
 
# File 'lib/resque/worker.rb', line 457

def hostname
  @hostname ||= `hostname`.chomp
end

#idle? ⇒ Boolean

Boolean - true if idle, false if not

Returns:

  • (Boolean) 


430
431
432
 
# File 'lib/resque/worker.rb', line 430

def idle?
  state == :idle
end

#inspect ⇒ Object 



445
446
447
 
# File 'lib/resque/worker.rb', line 445

def inspect
  "#<Worker #{to_s}>"
end

#job ⇒ Object Also known as: processing

Returns a hash explaining the Job we’re currently processing, if any.



418
419
420
421
 
# File 'lib/resque/worker.rb', line 418

def job
  worker = mongo_workers.find_one :worker => self.to_s
  worker.nil? ? { } : worker['working_on'] #decode(worker['working_on'])
end

#kill_child ⇒ Object

Kills the forked child immediately, without remorse. The job it is processing will not be completed.



279
280
281
282
283
284
285
286
287
288
289
 
# File 'lib/resque/worker.rb', line 279

def kill_child
  if @child
    log! "Killing child at #{@child}"
    if system("ps -o pid,state -p #{@child}")
      Process.kill("KILL", @child) rescue nil
    else
      log! "Child #{@child} not found, restarting."
      shutdown
    end
  end
end

#log(message) ⇒ Object

Log a message to STDOUT if we are verbose or very_verbose.



483
484
485
486
487
488
489
490
 
# File 'lib/resque/worker.rb', line 483

def log(message)
  if verbose
    puts "*** #{message}"
  elsif very_verbose
    time = Time.now.strftime('%H:%M:%S %Y-%m-%d')
    puts "** [#{time}] #$$: #{message}"
  end
end

#log!(message) ⇒ Object

Logs a very verbose message to STDOUT.



493
494
495
 
# File 'lib/resque/worker.rb', line 493

def log!(message)
  log message if very_verbose
end

#pause_processing ⇒ Object

Stop processing jobs after the current one has completed (if we’re currently running one).



298
299
300
301
 
# File 'lib/resque/worker.rb', line 298

def pause_processing
  log "USR2 received; pausing job processing"
  @paused = true
end

#paused? ⇒ Boolean

are we paused?

Returns:

  • (Boolean) 


292
293
294
 
# File 'lib/resque/worker.rb', line 292

def paused?
  @paused
end

#perform(job) ⇒ Object

Processes a given job in the child.



150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
 
# File 'lib/resque/worker.rb', line 150

def perform(job)
  begin
    run_hook :after_fork, job
    job.perform
  rescue Object => e
    log "#{job.inspect} failed: #{e.inspect}"
    begin
      job.fail(e)
    rescue Object => e
      log "Received exception when reporting failure: #{e.inspect}"
    end
    failed!
  else
    log "done: #{job.inspect}"
  ensure
    yield job if block_given?
  end
end

#pid ⇒ Object

Returns Integer PID of running worker



462
463
464
 
# File 'lib/resque/worker.rb', line 462

def pid
  @pid ||= to_s.split(":")[1].to_i
end

#process(job = nil, &block) ⇒ Object

DEPRECATED. Processes a single job. If none is given, it will try to produce one. Usually run in the child.



140
141
142
143
144
145
146
147
 
# File 'lib/resque/worker.rb', line 140

def process(job = nil, &block)
  return unless job ||= reserve

  working_on job
  perform(job, &block)
ensure
  done_working
end

#processed ⇒ Object

How many jobs has this worker processed? Returns an int.



385
386
387
 
# File 'lib/resque/worker.rb', line 385

def processed
  Stat["processed:#{self}"]
end

#processed! ⇒ Object

Tell Mongo we’ve processed a job.



390
391
392
393
 
# File 'lib/resque/worker.rb', line 390

def processed!
  Stat << "processed"
  Stat << "processed:#{self}"
end

#procline(string) ⇒ Object

Given a string, sets the procline ($0) and logs. Procline is always in the format of:

resque-VERSION: STRING



477
478
479
480
 
# File 'lib/resque/worker.rb', line 477

def procline(string)
  $0 = "resque-#{Resque::Version}: #{string}"
  log! $0
end

#prune_dead_workers ⇒ Object

Looks for any workers which should be running on this server and, if they’re not, removes them from Mongo.

This is a form of garbage collection. If a server is killed by a hard shutdown, power failure, or something else beyond our control, the Resque workers will not die gracefully and therefore will leave stale state information in Mongo.

By checking the current Mongo state against the actual environment, we can determine if Mongo is old and clean it up a bit.



319
320
321
322
323
324
325
326
327
328
329
 
# File 'lib/resque/worker.rb', line 319

def prune_dead_workers
  all_workers = Worker.all
  known_workers = worker_pids unless all_workers.empty?
  all_workers.each do |worker|
    host, pid, queues = worker.id.split(':')
    next unless host == hostname
    next if known_workers.include?(pid)
    log! "Pruning dead worker: #{worker}"
    worker.unregister_worker
  end
end

#queues ⇒ Object

Returns a list of queues to use when searching for a job. A splat (“*”) means you want every queue (in alpha order) - this can be useful for dynamically adding new queues.



190
191
192
 
# File 'lib/resque/worker.rb', line 190

def queues
  @queues[0] == "*" ? Resque.queues.sort : @queues
end

#register_signal_handlers ⇒ Object

Registers the various signal handlers a worker responds to.

TERM: Shutdown immediately, stop processing jobs.

INT: Shutdown immediately, stop processing jobs.

QUIT: Shutdown after the current job has finished processing. USR1: Kill the forked child immediately, continue processing jobs. USR2: Don’t process any new jobs CONT: Start processing jobs again after a USR2



243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
 
# File 'lib/resque/worker.rb', line 243

def register_signal_handlers
  trap('TERM') { shutdown!  }
  trap('INT')  { shutdown!  }

  begin
    trap('QUIT') { shutdown   }
    trap('USR1') { kill_child }
    trap('USR2') { pause_processing }
    trap('CONT') { unpause_processing }
  rescue ArgumentError
    warn "Signals QUIT, USR1, USR2, and/or CONT not supported."
  end

  log! "Registered signals"
end

#register_worker ⇒ Object

Registers ourself as a worker. Useful when entering the worker lifecycle on startup.



333
334
335
336
 
# File 'lib/resque/worker.rb', line 333

def register_worker
  mongo_workers << { :worker => self.to_s}
  started!
end

#reserve ⇒ Object

Attempts to grab a job off one of the provided queues. Returns nil if no job can be found.



171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
 
# File 'lib/resque/worker.rb', line 171

def reserve
  queues.each do |queue|
    log! "Checking #{queue}"
    if job = Resque::Job.reserve(queue)
      log! "Found job on #{queue}"
      return job
    end
  end

  nil
rescue Exception => e
  log "Error reserving job: #{e.inspect}"
  log e.backtrace.join("\n")
  raise e
end

#run_hook(name, *args) ⇒ Object

Runs a named hook, passing along any arguments.



339
340
341
342
343
344
345
346
 
# File 'lib/resque/worker.rb', line 339

def run_hook(name, *args)
  return unless hook = Resque.send(name)
  msg = "Running #{name} hook"
  msg << " with #{args.inspect}" if args.any?
  log msg

  args.any? ? hook.call(*args) : hook.call
end

#shutdown ⇒ Object

Schedule this worker for shutdown. Will finish processing the current job.



261
262
263
264
 
# File 'lib/resque/worker.rb', line 261

def shutdown
  log 'Exiting...'
  @shutdown = true
end

#shutdown! ⇒ Object

Kill the child and shutdown immediately.



267
268
269
270
 
# File 'lib/resque/worker.rb', line 267

def shutdown!
  shutdown
  kill_child
end

#shutdown? ⇒ Boolean

Should this worker shutdown as soon as current job is finished?

Returns:

  • (Boolean) 


273
274
275
 
# File 'lib/resque/worker.rb', line 273

def shutdown?
  @shutdown
end

#started ⇒ Object

What time did this worker start? Returns an instance of ‘Time`



407
408
409
410
 
# File 'lib/resque/worker.rb', line 407

def started
  worker = mongo_workers.find_one(:worker => self.to_s)
  worker.nil? ? nil : worker['started']
end

#started! ⇒ Object

Tell Mongo we’ve started



413
414
415
 
# File 'lib/resque/worker.rb', line 413

def started!
  mongo_workers.update({ :worker => self.to_s}, { '$set' => { :started => Time.now.to_s}})
end

#startup ⇒ Object

Runs all the methods needed when a worker begins its lifecycle.



215
216
217
218
219
220
221
222
223
224
225
 
# File 'lib/resque/worker.rb', line 215

def startup
  enable_gc_optimizations
  register_signal_handlers
  prune_dead_workers
  run_hook :before_first_fork
  register_worker

  # Fix buffering so we can `rake resque:work > resque.log` and
  # get output from the child in there.
  $stdout.sync = true
end

#state ⇒ Object

Returns a symbol representing the current worker state, which can be either :working or :idle



436
437
438
 
# File 'lib/resque/worker.rb', line 436

def state
  mongo_workers.find_one(:worker => self.to_s) ? :working : :idle
end

#unpause_processing ⇒ Object

Start processing jobs again after a pause



304
305
306
307
 
# File 'lib/resque/worker.rb', line 304

def unpause_processing
  log "CONT received; resuming job processing"
  @paused = false
end

#unregister_worker ⇒ Object

Unregisters ourself as a worker. Useful when shutting down.



349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
 
# File 'lib/resque/worker.rb', line 349

def unregister_worker
  # If we're still processing a job, make sure it gets logged as a
  # failure.
  if (hash = processing) && !hash.empty?
    job = Job.new(hash['queue'], hash['payload'])
    # Ensure the proper worker is attached to this job, even if
    # it's not the precise instance that died.
    job.worker = self
    job.fail(DirtyExit.new)
  end

  mongo_workers.remove :worker => self.to_s

  Stat.clear("processed:#{self}")
  Stat.clear("failed:#{self}")
end

#validate_queues ⇒ Object

A worker must be given a queue, otherwise it won’t know what to do with itself.

You probably never need to call this.



79
80
81
82
83
 
# File 'lib/resque/worker.rb', line 79

def validate_queues
  if @queues.nil? || @queues.empty?
    raise NoQueueError.new("Please give each worker at least one queue.")
  end
end

#work(interval = 5.0, &block) ⇒ Object

This is the main workhorse method. Called on a Worker instance, it begins the worker life cycle.

The following events occur during a worker’s life cycle:

  1. Startup: Signals are registered, dead workers are pruned,

    and this worker is registered.

  2. Work loop: Jobs are pulled from a queue and processed.

  3. Teardown: This worker is unregistered.

Can be passed a float representing the polling frequency. The default is 5 seconds, but for a semi-active site you may want to use a smaller value.

Also accepts a block which will be passed the job as soon as it has completed processing. Useful for testing.



101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
 
# File 'lib/resque/worker.rb', line 101

def work(interval = 5.0, &block)
  interval = Float(interval)
  $0 = "resque: Starting"
  startup

  loop do
    break if shutdown?

    if not paused? and job = reserve
      log "got: #{job.inspect}"
      run_hook :before_fork, job
      working_on job

      if @child = fork
        srand # Reseeding
        procline "Forked #{@child} at #{Time.now.to_i}"
        Process.wait
      else
        procline "Processing #{job.queue} since #{Time.now.to_i}"
        perform(job, &block)
        exit! unless @cant_fork
      end

      done_working
      @child = nil
    else
      break if interval.zero?
      log! "Sleeping for #{interval} seconds"
      procline paused? ? "Paused" : "Waiting for #{@queues.join(',')}"
      sleep interval
    end
  end

ensure
  unregister_worker
end

#worker_pids ⇒ Object

Returns an array of string pids of all the other workers on this machine. Useful when pruning dead workers on startup.



468
469
470
471
472
 
# File 'lib/resque/worker.rb', line 468

def worker_pids
  `ps -A -o pid,command | grep [r]esque | grep -v "resque-web"`.split("\n").map do |line|
    line.split(' ')[0]
  end
end

#working? ⇒ Boolean

Boolean - true if working, false if not

Returns:

  • (Boolean) 


425
426
427
 
# File 'lib/resque/worker.rb', line 425

def working?
  state == :working
end

#working_on(job) ⇒ Object

Given a job, tells Mongo we’re working on it. Useful for seeing what workers are doing and when.



368
369
370
371
372
373
374
375
 
# File 'lib/resque/worker.rb', line 368

def working_on(job)
  job.worker = self
  data = #encode \
    { :queue   => job.queue,
    :run_at  => Time.now.to_s,
    :payload => job.payload}
  mongo_workers.update({:worker => self.to_s}, { '$set' => { 'working_on' => data}}, :upsert => true)
end