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 = 
'3.0.3'

Class Method Summary collapse

Instance Method Summary collapse

Class Method Details

.included(klass) ⇒ Object 



9
10
11
 
# File 'lib/status_workflow.rb', line 9

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

.redis ⇒ Object 



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

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

.redis=(redis) ⇒ Object 



13
14
15
 
# 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, prefix = nil) ⇒ Object 



25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
 
# File 'lib/status_workflow.rb', line 25

def status_transition!(intermediate_to_status, final_to_status, prefix = nil)
  result = nil # what the block yields, return to the user
  before_status_transition = self.class.instance_variable_get(:@before_status_transition)
  intermediate_to_status = intermediate_to_status&.to_s
  final_to_status = final_to_status&.to_s
  prefix_ = prefix ? "#{prefix}_" : nil
  status_column = "#{prefix_}status"
  status_changed_at_column = "#{status_column}_changed_at"
  error_column = "#{status_column}_error"
  lock_obtained_at = nil
  lock_key = "status_workflow/#{self.class.name}/#{id}/#{status_column}"
  # 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 "#{prefix_}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_column => intermediate_to_status, status_changed_at_column => 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/2.0
          end
        end
        result = yield
        before_status_transition&.call
      rescue
        # If the block errors, set status to error and record the backtrace
        error = (["#{$!.class} #{$!.message}"] + $!.backtrace).join("\n")
        before_status_transition&.call
        status = read_attribute status_column
        update_columns status_column => "#{status}_error", status_changed_at_column => Time.now, error_column => error
        raise
      end
    end
    # Success!
    if intermediate_to_status
      send "#{prefix_}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_column => final_to_status, status_changed_at_column => 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
  result
end