Class: Gitlab::Ci::Runner::Backoff

Inherits:
Object
  • Object
show all
Defined in:
lib/gitlab/ci/runner/backoff.rb

Overview

Runner Backoff class is an implementation of an exponential backoff used when a runner communicates with GitLab. We typically use it when a runner retries sending a build status after we created a build pending state.

Backoff is calculated based on the backoff slot which is always a power of 2:

 0s -  3s   duration -> 1   second backoff
 4s -  7s   duration -> 2  seconds backoff
 8s - 15s   duration -> 4  seconds backoff
16s  - 31s  duration -> 8  seconds backoff
32s - 63s   duration -> 16 seconds backoff
64s - 127s  duration -> 32 seconds backoff

127s - 256s+ duration -> 64 seconds backoff

It means that first 15 requests made by a runner will need to respect following backoffs:

0s -> 1 second  backoff (backoff started, slot 0, 2^0 backoff)
1s -> 1 second  backoff
2s -> 1 second  backoff
3s -> 1 seconds backoff
                        (slot 1 - 2^1 backoff)
4s -> 2 seconds backoff
6s -> 2 seconds backoff
                        (slot 2 - 2^2 backoff)
8s -> 4 seconds backoff

12s -> 4 seconds backoff

(slot 3 - 2^3 backoff)

16s -> 8 seconds backoff 24s -> 8 seconds backoff

(slot 4 - 2^4 backoff)

32s -> 16 seconds backoff 48s -> 16 seconds backoff

(slot 5 - 2^5 backoff)

64s -> 32 seconds backoff 96s -> 32 seconds backoff

(slot 6 - 2^6 backoff)

128s -> 64 seconds backoff

There is a cap on the backoff - it will never exceed 64 seconds.

Instance Method Summary collapse

Constructor Details

#initialize(started) ⇒ Backoff

Returns a new instance of Backoff.



51
52
53
54
55
56
57
 
# File 'lib/gitlab/ci/runner/backoff.rb', line 51

def initialize(started)
  @started = started

  if duration < 0
    raise ArgumentError, 'backoff duration negative'
  end
end

Instance Method Details

#duration ⇒ Object 



59
60
61
 
# File 'lib/gitlab/ci/runner/backoff.rb', line 59

def duration
  (Time.current - @started).ceil
end

#slot ⇒ Object 



63
64
65
66
67
 
# File 'lib/gitlab/ci/runner/backoff.rb', line 63

def slot
  return 0 if duration < 2

  Math.log(duration, 2).floor - 1
end

#to_seconds ⇒ Object 



69
70
71
 
# File 'lib/gitlab/ci/runner/backoff.rb', line 69

def to_seconds
  2**[slot, 6].min
end