job.lua

-------------------------------------------------------------------------------
-- Job Class
--
-- It returns an object that represents the job with the provided JID
-------------------------------------------------------------------------------

-- This gets all the data associated with the job with the provided id. If the
-- job is not found, it returns nil. If found, it returns an object with the
-- appropriate properties
function QlessJob:data(...)
  local job = redis.call(
      'hmget', QlessJob.ns .. self.jid, 'jid', 'klass', 'state', 'queue',
      'worker', 'priority', 'expires', 'retries', 'remaining', 'data',
      'tags', 'failure', 'spawned_from_jid')

  -- Return nil if we haven't found it
  if not job[1] then
    return nil
  end

  local data = {
    jid              = job[1],
    klass            = job[2],
    state            = job[3],
    queue            = job[4],
    worker           = job[5] or '',
    tracked          = redis.call(
      'zscore', 'ql:tracked', self.jid) ~= false,
    priority         = tonumber(job[6]),
    expires          = tonumber(job[7]) or 0,
    retries          = tonumber(job[8]),
    remaining        = math.floor(tonumber(job[9])),
    data             = job[10],
    tags             = cjson.decode(job[11]),
    history          = self:history(),
    failure          = cjson.decode(job[12] or '{}'),
    spawned_from_jid = job[13],
    dependents       = redis.call(
      'smembers', QlessJob.ns .. self.jid .. '-dependents'),
    dependencies     = redis.call(
      'smembers', QlessJob.ns .. self.jid .. '-dependencies')
  }

  if #arg > 0 then
    -- This section could probably be optimized, but I wanted the interface
    -- in place first
    local response = {}
    for index, key in ipairs(arg) do
      table.insert(response, data[key])
    end
    return response
  else
    return data
  end
end

-- Complete a job and optionally put it in another queue, either scheduled or
-- to be considered waiting immediately. It can also optionally accept other
-- jids on which this job will be considered dependent before it's considered
-- valid.
--
-- The variable-length arguments may be pairs of the form:
--
--      ('next'   , queue) : The queue to advance it to next
--      ('delay'  , delay) : The delay for the next queue
--      ('depends',        : Json of jobs it depends on in the new queue
--          '["jid1", "jid2", ...]')
---
function QlessJob:complete(now, worker, queue, raw_data, ...)
  assert(worker, 'Complete(): Arg "worker" missing')
  assert(queue , 'Complete(): Arg "queue" missing')
  local data = assert(cjson.decode(raw_data),
    'Complete(): Arg "data" missing or not JSON: ' .. tostring(raw_data))

  -- Read in all the optional parameters
  local options = {}
  for i = 1, #arg, 2 do options[arg[i]] = arg[i + 1] end

  -- Sanity check on optional args
  local nextq   = options['next']
  local delay   = assert(tonumber(options['delay'] or 0))
  local depends = assert(cjson.decode(options['depends'] or '[]'),
    'Complete(): Arg "depends" not JSON: ' .. tostring(options['depends']))

  -- Depends doesn't make sense without nextq
  if options['delay'] and nextq == nil then
    error('Complete(): "delay" cannot be used without a "next".')
  end

  -- Depends doesn't make sense without nextq
  if options['depends'] and nextq == nil then
    error('Complete(): "depends" cannot be used without a "next".')
  end

  -- The bin is midnight of the provided day
  -- 24 * 60 * 60 = 86400
  local bin = now - (now % 86400)

  -- First things first, we should see if the worker still owns this job
  local lastworker, state, priority, retries, current_queue = unpack(
    redis.call('hmget', QlessJob.ns .. self.jid, 'worker', 'state',
      'priority', 'retries', 'queue'))

  if lastworker == false then
    error('Complete(): Job ' .. self.jid .. ' does not exist')
  elseif (state ~= 'running') then
    error('Complete(): Job ' .. self.jid .. ' is not currently running: ' ..
      state)
  elseif lastworker ~= worker then
    error('Complete(): Job ' .. self.jid ..
      ' has been handed out to another worker: ' .. tostring(lastworker))
  elseif queue ~= current_queue then
    error('Complete(): Job ' .. self.jid .. ' running in another queue: ' ..
      tostring(current_queue))
  end

  -- Now we can assume that the worker does own the job. We need to
  --    1) Remove the job from the 'locks' from the old queue
  --    2) Enqueue it in the next stage if necessary
  --    3) Update the data
  --    4) Mark the job as completed, remove the worker, remove expires, and
  --          update history
  self:history(now, 'done')

  if raw_data then
    redis.call('hset', QlessJob.ns .. self.jid, 'data', raw_data)
  end

  -- Remove the job from the previous queue
  local queue_obj = Qless.queue(queue)
  queue_obj.work.remove(self.jid)
  queue_obj.locks.remove(self.jid)
  queue_obj.scheduled.remove(self.jid)

  ----------------------------------------------------------
  -- This is the massive stats update that we have to do
  ----------------------------------------------------------
  -- This is how long we've been waiting to get popped
  -- local waiting = math.floor(now) - history[#history]['popped']
  local time = tonumber(
    redis.call('hget', QlessJob.ns .. self.jid, 'time') or now)
  local waiting = now - time
  Qless.queue(queue):stat(now, 'run', waiting)
  redis.call('hset', QlessJob.ns .. self.jid,
    'time', string.format("%.20f", now))

  -- Remove this job from the jobs that the worker that was running it has
  redis.call('zrem', 'ql:w:' .. worker .. ':jobs', self.jid)

  if redis.call('zscore', 'ql:tracked', self.jid) ~= false then
    Qless.publish('completed', self.jid)
  end

  if nextq then
    queue_obj = Qless.queue(nextq)
    -- Send a message out to log
    Qless.publish('log', cjson.encode({
      jid   = self.jid,
      event = 'advanced',
      queue = queue,
      to    = nextq
    }))

    -- Enqueue the job
    self:history(now, 'put', {q = nextq})

    -- We're going to make sure that this queue is in the
    -- set of known queues
    if redis.call('zscore', 'ql:queues', nextq) == false then
      redis.call('zadd', 'ql:queues', now, nextq)
    end

    redis.call('hmset', QlessJob.ns .. self.jid,
      'state', 'waiting',
      'worker', '',
      'failure', '{}',
      'queue', nextq,
      'expires', 0,
      'remaining', tonumber(retries))

    if (delay > 0) and (#depends == 0) then
      queue_obj.scheduled.add(now + delay, self.jid)
      return 'scheduled'
    else
      -- These are the jids we legitimately have to wait on
      local count = 0
      for i, j in ipairs(depends) do
        -- Make sure it's something other than 'nil' or complete.
        local state = redis.call('hget', QlessJob.ns .. j, 'state')
        if (state and state ~= 'complete') then
          count = count + 1
          redis.call(
            'sadd', QlessJob.ns .. j .. '-dependents',self.jid)
          redis.call(
            'sadd', QlessJob.ns .. self.jid .. '-dependencies', j)
        end
      end
      if count > 0 then
        queue_obj.depends.add(now, self.jid)
        redis.call('hset', QlessJob.ns .. self.jid, 'state', 'depends')
        if delay > 0 then
          -- We've already put it in 'depends'. Now, we must just save the data
          -- for when it's scheduled
          queue_obj.depends.add(now, self.jid)
          redis.call('hset', QlessJob.ns .. self.jid, 'scheduled', now + delay)
        end
        return 'depends'
      else
        queue_obj.work.add(now, priority, self.jid)
        return 'waiting'
      end
    end
  else
    -- Send a message out to log
    Qless.publish('log', cjson.encode({
      jid   = self.jid,
      event = 'completed',
      queue = queue
    }))

    redis.call('hmset', QlessJob.ns .. self.jid,
      'state', 'complete',
      'worker', '',
      'failure', '{}',
      'queue', '',
      'expires', 0,
      'remaining', tonumber(retries))

    -- Do the completion dance
    local count = Qless.config.get('jobs-history-count')
    local time  = Qless.config.get('jobs-history')

    -- These are the default values
    count = tonumber(count or 50000)
    time  = tonumber(time  or 7 * 24 * 60 * 60)

    -- Schedule this job for destructination eventually
    redis.call('zadd', 'ql:completed', now, self.jid)

    -- Now look at the expired job data. First, based on the current time
    local jids = redis.call('zrangebyscore', 'ql:completed', 0, now - time)
    -- Any jobs that need to be expired... delete
    for index, jid in ipairs(jids) do
      local tags = cjson.decode(
        redis.call('hget', QlessJob.ns .. jid, 'tags') or '{}')
      for i, tag in ipairs(tags) do
        redis.call('zrem', 'ql:t:' .. tag, jid)
        redis.call('zincrby', 'ql:tags', -1, tag)
      end
      redis.call('del', QlessJob.ns .. jid)
      redis.call('del', QlessJob.ns .. jid .. '-history')
    end
    -- And now remove those from the queued-for-cleanup queue
    redis.call('zremrangebyscore', 'ql:completed', 0, now - time)

    -- Now take the all by the most recent 'count' ids
    jids = redis.call('zrange', 'ql:completed', 0, (-1-count))
    for index, jid in ipairs(jids) do
      local tags = cjson.decode(
        redis.call('hget', QlessJob.ns .. jid, 'tags') or '{}')
      for i, tag in ipairs(tags) do
        redis.call('zrem', 'ql:t:' .. tag, jid)
        redis.call('zincrby', 'ql:tags', -1, tag)
      end
      redis.call('del', QlessJob.ns .. jid)
      redis.call('del', QlessJob.ns .. jid .. '-history')
    end
    redis.call('zremrangebyrank', 'ql:completed', 0, (-1-count))

    -- Alright, if this has any dependents, then we should go ahead
    -- and unstick those guys.
    for i, j in ipairs(redis.call(
      'smembers', QlessJob.ns .. self.jid .. '-dependents')) do
      redis.call('srem', QlessJob.ns .. j .. '-dependencies', self.jid)
      if redis.call(
        'scard', QlessJob.ns .. j .. '-dependencies') == 0 then
        local q, p, scheduled = unpack(
          redis.call('hmget', QlessJob.ns .. j, 'queue', 'priority', 'scheduled'))
        if q then
          local queue = Qless.queue(q)
          queue.depends.remove(j)
          if scheduled then
            queue.scheduled.add(scheduled, j)
            redis.call('hset', QlessJob.ns .. j, 'state', 'scheduled')
            redis.call('hdel', QlessJob.ns .. j, 'scheduled')
          else
            queue.work.add(now, p, j)
            redis.call('hset', QlessJob.ns .. j, 'state', 'waiting')
          end
        end
      end
    end

    -- Delete our dependents key
    redis.call('del', QlessJob.ns .. self.jid .. '-dependents')

    return 'complete'
  end
end

-- Fail(now, worker, group, message, [data])
-- -------------------------------------------------
-- Mark the particular job as failed, with the provided group, and a more
-- specific message. By `group`, we mean some phrase that might be one of
-- several categorical modes of failure. The `message` is something more
-- job-specific, like perhaps a traceback.
--
-- This method should __not__ be used to note that a job has been dropped or
-- has failed in a transient way. This method __should__ be used to note that
-- a job has something really wrong with it that must be remedied.
--
-- The motivation behind the `group` is so that similar errors can be grouped
-- together. Optionally, updated data can be provided for the job. A job in
-- any state can be marked as failed. If it has been given to a worker as a
-- job, then its subsequent requests to heartbeat or complete that job will
-- fail. Failed jobs are kept until they are canceled or completed.
--
-- __Returns__ the id of the failed job if successful, or `False` on failure.
--
-- Args:
--    1) jid
--    2) worker
--    3) group
--    4) message
--    5) the current time
--    6) [data]
function QlessJob:fail(now, worker, group, message, data)
  local worker  = assert(worker           , 'Fail(): Arg "worker" missing')
  local group   = assert(group            , 'Fail(): Arg "group" missing')
  local message = assert(message          , 'Fail(): Arg "message" missing')

  -- The bin is midnight of the provided day
  -- 24 * 60 * 60 = 86400
  local bin = now - (now % 86400)

  if data then
    data = cjson.decode(data)
  end

  -- First things first, we should get the history
  local queue, state, oldworker = unpack(redis.call(
    'hmget', QlessJob.ns .. self.jid, 'queue', 'state', 'worker'))

  -- If the job has been completed, we cannot fail it
  if not state then
    error('Fail(): Job ' .. self.jid .. 'does not exist')
  elseif state ~= 'running' then
    error('Fail(): Job ' .. self.jid .. 'not currently running: ' .. state)
  elseif worker ~= oldworker then
    error('Fail(): Job ' .. self.jid .. ' running with another worker: ' ..
      oldworker)
  end

  -- Send out a log message
  Qless.publish('log', cjson.encode({
    jid     = self.jid,
    event   = 'failed',
    worker  = worker,
    group   = group,
    message = message
  }))

  if redis.call('zscore', 'ql:tracked', self.jid) ~= false then
    Qless.publish('failed', self.jid)
  end

  -- Remove this job from the jobs that the worker that was running it has
  redis.call('zrem', 'ql:w:' .. worker .. ':jobs', self.jid)

  -- Now, take the element of the history for which our provided worker is
  -- the worker, and update 'failed'
  self:history(now, 'failed', {worker = worker, group = group})

  -- Increment the number of failures for that queue for the
  -- given day.
  redis.call('hincrby', 'ql:s:stats:' .. bin .. ':' .. queue, 'failures', 1)
  redis.call('hincrby', 'ql:s:stats:' .. bin .. ':' .. queue, 'failed'  , 1)

  -- Now remove the instance from the schedule, and work queues for the
  -- queue it's in
  local queue_obj = Qless.queue(queue)
  queue_obj.work.remove(self.jid)
  queue_obj.locks.remove(self.jid)
  queue_obj.scheduled.remove(self.jid)

  -- The reason that this appears here is that the above will fail if the
  -- job doesn't exist
  if data then
    redis.call('hset', QlessJob.ns .. self.jid, 'data', cjson.encode(data))
  end

  redis.call('hmset', QlessJob.ns .. self.jid,
    'state', 'failed',
    'worker', '',
    'expires', '',
    'failure', cjson.encode({
      ['group']   = group,
      ['message'] = message,
      ['when']    = math.floor(now),
      ['worker']  = worker
    }))

  -- Add this group of failure to the list of failures
  redis.call('sadd', 'ql:failures', group)
  -- And add this particular instance to the failed groups
  redis.call('lpush', 'ql:f:' .. group, self.jid)

  -- Here is where we'd intcrement stats about the particular stage
  -- and possibly the workers

  return self.jid
end

-- retry(now, queue, worker, [delay, [group, [message]]])
-- ------------------------------------------
-- This script accepts jid, queue, worker and delay for retrying a job. This
-- is similar in functionality to `put`, except that this counts against the
-- retries a job has for a stage.
--
-- Throws an exception if:
--      - the worker is not the worker with a lock on the job
--      - the job is not actually running
--
-- Otherwise, it returns the number of retries remaining. If the allowed
-- retries have been exhausted, then it is automatically failed, and a negative
-- number is returned.
--
-- If a group and message is provided, then if the retries are exhausted, then
-- the provided group and message will be used in place of the default
-- messaging about retries in the particular queue being exhausted
function QlessJob:retry(now, queue, worker, delay, group, message)
  assert(queue , 'Retry(): Arg "queue" missing')
  assert(worker, 'Retry(): Arg "worker" missing')
  delay = assert(tonumber(delay or 0),
    'Retry(): Arg "delay" not a number: ' .. tostring(delay))

  -- Let's see what the old priority, and tags were
  local oldqueue, state, retries, oldworker, priority, failure = unpack(
    redis.call('hmget', QlessJob.ns .. self.jid, 'queue', 'state',
      'retries', 'worker', 'priority', 'failure'))

  -- If this isn't the worker that owns
  if oldworker == false then
    error('Retry(): Job ' .. self.jid .. ' does not exist')
  elseif state ~= 'running' then
    error('Retry(): Job ' .. self.jid .. ' is not currently running: ' ..
      state)
  elseif oldworker ~= worker then
    error('Retry(): Job ' .. self.jid ..
      ' has been given to another worker: ' .. oldworker)
  end

  -- For each of these, decrement their retries. If any of them
  -- have exhausted their retries, then we should mark them as
  -- failed.
  local remaining = tonumber(redis.call(
    'hincrby', QlessJob.ns .. self.jid, 'remaining', -1))
  redis.call('hdel', QlessJob.ns .. self.jid, 'grace')

  -- Remove it from the locks key of the old queue
  Qless.queue(oldqueue).locks.remove(self.jid)

  -- Remove this job from the worker that was previously working it
  redis.call('zrem', 'ql:w:' .. worker .. ':jobs', self.jid)

  if remaining < 0 then
    -- Now remove the instance from the schedule, and work queues for the
    -- queue it's in
    local group = group or 'failed-retries-' .. queue
    self:history(now, 'failed', {['group'] = group})

    redis.call('hmset', QlessJob.ns .. self.jid, 'state', 'failed',
      'worker', '',
      'expires', '')
    -- If the failure has not already been set, then set it
    if group ~= nil and message ~= nil then
      redis.call('hset', QlessJob.ns .. self.jid,
        'failure', cjson.encode({
          ['group']   = group,
          ['message'] = message,
          ['when']    = math.floor(now),
          ['worker']  = worker
        })
      )
    else
      redis.call('hset', QlessJob.ns .. self.jid,
      'failure', cjson.encode({
        ['group']   = group,
        ['message'] =
          'Job exhausted retries in queue "' .. oldqueue .. '"',
        ['when']    = now,
        ['worker']  = unpack(self:data('worker'))
      }))
    end

    if redis.call('zscore', 'ql:tracked', self.jid) ~= false then
      Qless.publish('failed', self.jid)
    end

    -- Add this type of failure to the list of failures
    redis.call('sadd', 'ql:failures', group)
    -- And add this particular instance to the failed types
    redis.call('lpush', 'ql:f:' .. group, self.jid)
    -- Increment the count of the failed jobs
    local bin = now - (now % 86400)
    redis.call('hincrby', 'ql:s:stats:' .. bin .. ':' .. queue, 'failures', 1)
    redis.call('hincrby', 'ql:s:stats:' .. bin .. ':' .. queue, 'failed'  , 1)
  else
    -- Put it in the queue again with a delay. Like put()
    local queue_obj = Qless.queue(queue)
    if delay > 0 then
      queue_obj.scheduled.add(now + delay, self.jid)
      redis.call('hset', QlessJob.ns .. self.jid, 'state', 'scheduled')
    else
      queue_obj.work.add(now, priority, self.jid)
      redis.call('hset', QlessJob.ns .. self.jid, 'state', 'waiting')
    end

    -- If a group and a message was provided, then we should save it
    if group ~= nil and message ~= nil then
      redis.call('hset', QlessJob.ns .. self.jid,
        'failure', cjson.encode({
          ['group']   = group,
          ['message'] = message,
          ['when']    = math.floor(now),
          ['worker']  = worker
        })
      )
    end
  end

  return math.floor(remaining)
end

-- Depends(jid, 'on', [jid, [jid, [...]]]
-- Depends(jid, 'off', [jid, [jid, [...]]])
-- Depends(jid, 'off', 'all')
-------------------------------------------------------------------------------
-- Add or remove dependencies a job has. If 'on' is provided, the provided
-- jids are added as dependencies. If 'off' and 'all' are provided, then all
-- the current dependencies are removed. If 'off' is provided and the next
-- argument is not 'all', then those jids are removed as dependencies.
--
-- If a job is not already in the 'depends' state, then this call will return
-- false. Otherwise, it will return true
function QlessJob:depends(now, command, ...)
  assert(command, 'Depends(): Arg "command" missing')
  local state = redis.call('hget', QlessJob.ns .. self.jid, 'state')
  if state ~= 'depends' then
    error('Depends(): Job ' .. self.jid ..
      ' not in the depends state: ' .. tostring(state))
  end

  if command == 'on' then
    -- These are the jids we legitimately have to wait on
    for i, j in ipairs(arg) do
      -- Make sure it's something other than 'nil' or complete.
      local state = redis.call('hget', QlessJob.ns .. j, 'state')
      if (state and state ~= 'complete') then
        redis.call(
          'sadd', QlessJob.ns .. j .. '-dependents'  , self.jid)
        redis.call(
          'sadd', QlessJob.ns .. self.jid .. '-dependencies', j)
      end
    end
    return true
  elseif command == 'off' then
    if arg[1] == 'all' then
      for i, j in ipairs(redis.call(
        'smembers', QlessJob.ns .. self.jid .. '-dependencies')) do
        redis.call('srem', QlessJob.ns .. j .. '-dependents', self.jid)
      end
      redis.call('del', QlessJob.ns .. self.jid .. '-dependencies')
      local q, p = unpack(redis.call(
        'hmget', QlessJob.ns .. self.jid, 'queue', 'priority'))
      if q then
        local queue_obj = Qless.queue(q)
        queue_obj.depends.remove(self.jid)
        queue_obj.work.add(now, p, self.jid)
        redis.call('hset', QlessJob.ns .. self.jid, 'state', 'waiting')
      end
    else
      for i, j in ipairs(arg) do
        redis.call('srem', QlessJob.ns .. j .. '-dependents', self.jid)
        redis.call(
          'srem', QlessJob.ns .. self.jid .. '-dependencies', j)
        if redis.call('scard',
          QlessJob.ns .. self.jid .. '-dependencies') == 0 then
          local q, p = unpack(redis.call(
            'hmget', QlessJob.ns .. self.jid, 'queue', 'priority'))
          if q then
            local queue_obj = Qless.queue(q)
            queue_obj.depends.remove(self.jid)
            queue_obj.work.add(now, p, self.jid)
            redis.call('hset',
              QlessJob.ns .. self.jid, 'state', 'waiting')
          end
        end
      end
    end
    return true
  else
    error('Depends(): Argument "command" must be "on" or "off"')
  end
end

-- Heartbeat
------------
-- Renew this worker's lock on this job. Throws an exception if:
--      - the job's been given to another worker
--      - the job's been completed
--      - the job's been canceled
--      - the job's not running
function QlessJob:heartbeat(now, worker, data)
  assert(worker, 'Heatbeat(): Arg "worker" missing')

  -- We should find the heartbeat interval for this queue
  -- heartbeat. First, though, we need to find the queue
  -- this particular job is in
  local queue = redis.call('hget', QlessJob.ns .. self.jid, 'queue') or ''
  local expires = now + tonumber(
    Qless.config.get(queue .. '-heartbeat') or
    Qless.config.get('heartbeat', 60))

  if data then
    data = cjson.decode(data)
  end

  -- First, let's see if the worker still owns this job, and there is a
  -- worker
  local job_worker, state = unpack(
    redis.call('hmget', QlessJob.ns .. self.jid, 'worker', 'state'))
  if job_worker == false then
    -- This means the job doesn't exist
    error('Heartbeat(): Job ' .. self.jid .. ' does not exist')
  elseif state ~= 'running' then
    error(
      'Heartbeat(): Job ' .. self.jid .. ' not currently running: ' .. state)
  elseif job_worker ~= worker or #job_worker == 0 then
    error(
      'Heartbeat(): Job ' .. self.jid ..
      ' given out to another worker: ' .. job_worker)
  else
    -- Otherwise, optionally update the user data, and the heartbeat
    if data then
      -- I don't know if this is wise, but I'm decoding and encoding
      -- the user data to hopefully ensure its sanity
      redis.call('hmset', QlessJob.ns .. self.jid, 'expires',
        expires, 'worker', worker, 'data', cjson.encode(data))
    else
      redis.call('hmset', QlessJob.ns .. self.jid,
        'expires', expires, 'worker', worker)
    end

    -- Update hwen this job was last updated on that worker
    -- Add this job to the list of jobs handled by this worker
    redis.call('zadd', 'ql:w:' .. worker .. ':jobs', expires, self.jid)

    -- Make sure we this worker to the list of seen workers
    redis.call('zadd', 'ql:workers', now, worker)

    -- And now we should just update the locks
    local queue = Qless.queue(
      redis.call('hget', QlessJob.ns .. self.jid, 'queue'))
    queue.locks.add(expires, self.jid)
    return expires
  end
end

-- Priority
-- --------
-- Update the priority of this job. If the job doesn't exist, throws an
-- exception
function QlessJob:priority(priority)
  priority = assert(tonumber(priority),
    'Priority(): Arg "priority" missing or not a number: ' ..
    tostring(priority))

  -- Get the queue the job is currently in, if any
  local queue = redis.call('hget', QlessJob.ns .. self.jid, 'queue')

  if queue == nil or queue == false then
    -- If the job doesn't exist, throw an error
    error('Priority(): Job ' .. self.jid .. ' does not exist')
  elseif queue == '' then
    -- Just adjust the priority
    redis.call('hset', QlessJob.ns .. self.jid, 'priority', priority)
    return priority
  else
    -- Adjust the priority and see if it's a candidate for updating
    -- its priority in the queue it's currently in
    local queue_obj = Qless.queue(queue)
    if queue_obj.work.score(self.jid) then
      queue_obj.work.add(0, priority, self.jid)
    end
    redis.call('hset', QlessJob.ns .. self.jid, 'priority', priority)
    return priority
  end
end

-- Update the jobs' attributes with the provided dictionary
function QlessJob:update(data)
  local tmp = {}
  for k, v in pairs(data) do
    table.insert(tmp, k)
    table.insert(tmp, v)
  end
  redis.call('hmset', QlessJob.ns .. self.jid, unpack(tmp))
end

-- Times out the job now rather than when its lock is normally set to expire
function QlessJob:timeout(now)
  local queue_name, state, worker = unpack(redis.call('hmget',
    QlessJob.ns .. self.jid, 'queue', 'state', 'worker'))
  if queue_name == nil or queue_name == false then
    error('Timeout(): Job ' .. self.jid .. ' does not exist')
  elseif state ~= 'running' then
    error('Timeout(): Job ' .. self.jid .. ' not running')
  else
    -- Time out the job
    self:history(now, 'timed-out')
    local queue = Qless.queue(queue_name)
    queue.locks.remove(self.jid)
    queue.work.add(now, '+inf', self.jid)
    redis.call('hmset', QlessJob.ns .. self.jid,
      'state', 'stalled', 'expires', 0)
    local encoded = cjson.encode({
      jid    = self.jid,
      event  = 'lock_lost',
      worker = worker
    })
    Qless.publish('w:' .. worker, encoded)
    Qless.publish('log', encoded)
    return queue_name
  end
end

-- Return whether or not this job exists
function QlessJob:exists()
  return redis.call('exists', QlessJob.ns .. self.jid) == 1
end

-- Get or append to history
function QlessJob:history(now, what, item)
  -- First, check if there's an old-style history, and update it if there is
  local history = redis.call('hget', QlessJob.ns .. self.jid, 'history')
  if history then
    history = cjson.decode(history)
    for i, value in ipairs(history) do
      redis.call('rpush', QlessJob.ns .. self.jid .. '-history',
        cjson.encode({math.floor(value.put), 'put', {q = value.q}}))

      -- If there's any popped time
      if value.popped then
        redis.call('rpush', QlessJob.ns .. self.jid .. '-history',
          cjson.encode({math.floor(value.popped), 'popped',
            {worker = value.worker}}))
      end

      -- If there's any failure
      if value.failed then
        redis.call('rpush', QlessJob.ns .. self.jid .. '-history',
          cjson.encode(
            {math.floor(value.failed), 'failed', nil}))
      end

      -- If it was completed
      if value.done then
        redis.call('rpush', QlessJob.ns .. self.jid .. '-history',
          cjson.encode(
            {math.floor(value.done), 'done', nil}))
      end
    end
    -- With all this ported forward, delete the old-style history
    redis.call('hdel', QlessJob.ns .. self.jid, 'history')
  end

  -- Now to the meat of the function
  if what == nil then
    -- Get the history
    local response = {}
    for i, value in ipairs(redis.call('lrange',
      QlessJob.ns .. self.jid .. '-history', 0, -1)) do
      value = cjson.decode(value)
      local dict = value[3] or {}
      dict['when'] = value[1]
      dict['what'] = value[2]
      table.insert(response, dict)
    end
    return response
  else
    -- Append to the history. If the length of the history should be limited,
    -- then we'll truncate it.
    local count = tonumber(Qless.config.get('max-job-history', 100))
    if count > 0 then
      -- We'll always keep the first item around
      local obj = redis.call('lpop', QlessJob.ns .. self.jid .. '-history')
      redis.call('ltrim', QlessJob.ns .. self.jid .. '-history', -count + 2, -1)
      if obj ~= nil and obj ~= false then
        redis.call('lpush', QlessJob.ns .. self.jid .. '-history', obj)
      end
    end
    return redis.call('rpush', QlessJob.ns .. self.jid .. '-history',
      cjson.encode({math.floor(now), what, item}))
  end
end