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-module Gitlab
- module Ci
- # # 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.
- module PipelineDuration
- extend self
-
- Period = Struct.new(:first, :last) do
- def duration
- last - first
- end
- end
-
- 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
-
- 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
-
- # periods should be sorted by `first`
- def from_periods(periods)
- process_duration(process_periods(periods))
- end
-
- private
-
- def process_periods(periods)
- return periods if periods.empty?
-
- periods.drop(1).inject([periods.first]) do |result, current|
- previous = result.last
-
- if overlap?(previous, current)
- result[-1] = merge(previous, current)
- result
- else
- result << current
- end
- end
- end
-
- def overlap?(previous, current)
- current.first <= previous.last
- end
-
- def merge(previous, current)
- Period.new(previous.first, [previous.last, current.last].max)
- end
-
- def process_duration(periods)
- periods.sum(&:duration)
- end
- end
- end
-end