Module: Gitlab::Ci::Pipeline::Duration

Extended by:
Duration
Included in:
Duration
Defined in:
lib/gitlab/ci/pipeline/duration.rb

Overview

# Introduction - total running time

The problem this module is trying to solve is finding the total running time amongst all the jobs, excluding retries and pending (queue) time. We could reduce this problem down to finding the union of periods.

So each job would be represented as a `Period`, which consists of `Period#first` as when the job started and `Period#last` as when the job was finished. A simple example here would be:

  • A (1, 3)

  • B (2, 4)

  • C (6, 7)

Here A begins from 1, and ends to 3. B begins from 2, and ends to 4. C begins from 6, and ends to 7. Visually it could be viewed as:

0  1  2  3  4  5  6  7
   AAAAAAA
      BBBBBBB
                  CCCC

The union of A, B, and C would be (1, 4) and (6, 7), therefore the total running time should be:

(4 - 1) + (7 - 6) => 4

# The Algorithm

The algorithm used here for union would be described as follow. First we make sure that all periods are sorted by `Period#first`. Then we try to merge periods by iterating through the first period to the last period. The goal would be merging all overlapped periods so that in the end all the periods are discrete. When all periods are discrete, we're free to just sum all the periods to get real running time.

Here we begin from A, and compare it to B. We could find that before A ends, B already started. That is `B.first <= A.last` that is `2 <= 3` which means A and B are overlapping!

When we found that two periods are overlapping, we would need to merge them into a new period and disregard the old periods. To make a new period, we take `A.first` as the new first because remember? we sorted them, so `A.first` must be smaller or equal to `B.first`. And we take `[A.last, B.last].max` as the new last because we want whoever ended later. This could be broken into two cases:

0  1  2  3  4
   AAAAAAA
      BBBBBBB

Or:

0  1  2  3  4
   AAAAAAAAAA
      BBBB

So that we need to take whoever ends later. Back to our example, after merging and discard A and B it could be visually viewed as:

0  1  2  3  4  5  6  7
   DDDDDDDDDD
                  CCCC

Now we could go on and compare the newly created D and the old C. We could figure out that D and C are not overlapping by checking `C.first <= D.last` is `false`. Therefore we need to keep both C and D. The example would end here because there are no more jobs.

After having the union of all periods, we just need to sum the length of all periods to get total time.

(4 - 1) + (7 - 6) => 4

That is 4 is the answer in the example.

Defined Under Namespace

Classes: Period

Instance Method Summary collapse

Instance Method Details

#from_builds(builds) ⇒ Object

rubocop: enable CodeReuse/ActiveRecord


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# File 'lib/gitlab/ci/pipeline/duration.rb', line 101

def from_builds(builds)
  now = Time.now

  periods = builds.map do |b|
    Period.new(b.started_at, b.finished_at || now)
  end

  from_periods(periods)
end

#from_periods(periods) ⇒ Object

periods should be sorted by `first`


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# File 'lib/gitlab/ci/pipeline/duration.rb', line 112

def from_periods(periods)
  process_duration(process_periods(periods))
end

#from_pipeline(pipeline) ⇒ Object

rubocop: disable CodeReuse/ActiveRecord


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# File 'lib/gitlab/ci/pipeline/duration.rb', line 92

def from_pipeline(pipeline)
  status = %w[success failed running canceled]
  builds = pipeline.builds.latest
    .where(status: status).where.not(started_at: nil).order(:started_at)

  from_builds(builds)
end