Module: StatusWorkflow

Defined in:
lib/status_workflow.rb,
lib/status_workflow/version.rb

Defined Under Namespace

Modules: ClassMethods Classes: InvalidTransition, TooSlow

Constant Summary collapse

LOCK_ACQUISITION_TIMEOUT = 
8
LOCK_EXPIRY = 
4
LOCK_CHECK_RATE = 
0.2
VERSION = 
'2.0.0'

Class Method Summary collapse

Instance Method Summary collapse

Class Method Details

.included(klass) ⇒ Object 



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# File 'lib/status_workflow.rb', line 9

def self.included(klass)
  klass.extend ClassMethods
end

.redis ⇒ Object 



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# File 'lib/status_workflow.rb', line 17

def self.redis
  @redis or raise("please set StatusWorkflow.redis=")
end

.redis=(redis) ⇒ Object 



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# File 'lib/status_workflow.rb', line 13

def self.redis=(redis)
  @redis = redis
end

Instance Method Details

#status_transition!(intermediate_to_status, final_to_status) ⇒ Object 



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# File 'lib/status_workflow.rb', line 25

def status_transition!(intermediate_to_status, final_to_status)
  intermediate_to_status = intermediate_to_status&.to_s
  final_to_status = final_to_status&.to_s
  lock_obtained_at = nil
  lock_key = "status_workflow/#{self.class.name}/#{id}"
  # Give ourselves 8 seconds to get the lock, checking every 0.2 seconds
  Timeout.timeout(LOCK_ACQUISITION_TIMEOUT, nil, "#{lock_key} timeout waiting for lock") do
    until StatusWorkflow.redis.set(lock_key, true, nx: true, ex: LOCK_EXPIRY)
      sleep LOCK_CHECK_RATE
    end
    lock_obtained_at = Time.now
  end
  heartbeat = nil
  initial_to_status = intermediate_to_status || final_to_status
  begin
    # depend on #can_enter_X to reload
    send "can_enter_#{initial_to_status}?", true
    raise TooSlow, "#{lock_key} lost lock after checking status" if Time.now - lock_obtained_at > LOCK_EXPIRY
    if intermediate_to_status
      update_columns status: intermediate_to_status, status_changed_at: Time.now
      raise TooSlow, "#{lock_key} lost lock after setting intermediate status #{intermediate_to_status}" if Time.now - lock_obtained_at > LOCK_EXPIRY
    end
    # If a block was given, start a heartbeat thread
    if block_given?
      begin
        heartbeat = Thread.new do
          loop do
            StatusWorkflow.redis.expire lock_key, LOCK_EXPIRY
            lock_obtained_at = Time.now
            sleep LOCK_EXPIRY/2
          end
        end
        yield
      rescue
        # If the block errors, set status to error and record the backtrace
        error = (["#{$!.class} #{$!.message}"] + $!.backtrace).join("\n")
        update_columns status: 'error', status_changed_at: Time.now, error: error
        raise
      end
    end
    # Success!
    if intermediate_to_status
      send "can_enter_#{final_to_status}?", true
      raise TooSlow, "#{lock_key} lost lock after checking final status" if Time.now - lock_obtained_at > LOCK_EXPIRY
    end
    update_columns status: final_to_status, status_changed_at: Time.now
  ensure
    raise TooSlow, "#{lock_key} lost lock" if Time.now - lock_obtained_at > LOCK_EXPIRY
    StatusWorkflow.redis.del lock_key
    heartbeat.kill if heartbeat
  end
  true
end