65 行
1.8 KiB
Ruby
65 行
1.8 KiB
Ruby
module Preview
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class Screenshot
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class Unavailable < StandardError; end
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class Busy < Unavailable; end
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class TimedOut < Unavailable; end
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LIMIT = ENV.fetch('PREVIEW_SCREENSHOT_CONCURRENCY', 2).to_i.clamp(1, 10)
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TIMEOUT = ENV.fetch('PREVIEW_SCREENSHOT_TIMEOUT', 20).to_i.clamp(5, 60)
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@mutex = Mutex.new
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@active = 0
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def self.capture(url)
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acquire!
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tempfile = nil
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pid = nil
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begin
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tempfile = Tempfile.new(['preview-thumbnail', '.png'])
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tempfile.close
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status = nil
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pid = Process.spawn(
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'node', Rails.root.join('lib/screenshot.js').to_s,
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url, tempfile.path,
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out: File::NULL, err: File::NULL, pgroup: true)
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Timeout.timeout(TIMEOUT) do
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_finished_pid, status = Process.wait2(pid)
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end
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raise Unavailable, 'スクリーンショットを生成できませんでした．' unless status.success?
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raise Unavailable, 'スクリーンショットを生成できませんでした．' unless File.size?(tempfile.path)
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File.binread(tempfile.path)
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rescue Timeout::Error
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terminate(pid)
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raise TimedOut, 'スクリーンショット生成が timeout しました．'
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ensure
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tempfile&.unlink
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release!
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end
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end
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def self.acquire!
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@mutex.synchronize do
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raise Busy, 'スクリーンショット生成が混雑してゐます．' if @active >= LIMIT
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@active += 1
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end
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end
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def self.release!
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@mutex.synchronize { @active -= 1 }
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end
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def self.terminate(pid)
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return unless pid
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Process.kill('TERM', -pid)
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Process.wait(pid)
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rescue Errno::ESRCH, Errno::ECHILD
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nil
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end
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private_class_method :acquire!, :release!, :terminate
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end
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end
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