Class: FetchUtil::ParallelFetcher

Inherits:
Object
  • Object
show all
Defined in:
lib/fetch_util/parallel_fetcher.rb

Defined Under Namespace

Classes: Failure, ParallelFetchError

Constant Summary collapse

DEFAULT_CONCURRENCY = 
4

Instance Method Summary collapse

Constructor Details

#initialize(fetcher_factory: nil, concurrency: DEFAULT_CONCURRENCY, **fetch_options) ⇒ ParallelFetcher

Returns a new instance of ParallelFetcher.



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# File 'lib/fetch_util/parallel_fetcher.rb', line 32

def initialize(fetcher_factory: nil, concurrency: DEFAULT_CONCURRENCY, **fetch_options)
  @fetcher_factory = fetcher_factory || -> { Fetcher.new(**fetch_options) }
  @concurrency = [concurrency.to_i, 1].max
end

Instance Method Details

#fetch(urls) ⇒ Object 



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# File 'lib/fetch_util/parallel_fetcher.rb', line 37

def fetch(urls)
  work = Array(urls).compact.map(&:to_s).reject(&:empty?)
  return [] if work.empty?

  results = Array.new(work.length)
  worker_count = [@concurrency, work.length].min
  failures = []
  next_index = 0
  mutex = Mutex.new

  threads = Array.new(worker_count) do
    Thread.new do
      fetcher = @fetcher_factory.call

      begin
        loop do
          index = mutex.synchronize do
            if next_index < work.length
              current = next_index
              next_index += 1
              current
            end
          end
          break if index.nil?

          url = work[index]

          begin
            results[index] = fetcher.fetch(url)
          rescue StandardError => e
            mutex.synchronize { failures << Failure.new(index: index, url: url, error: e) }
          end
        end
      ensure
        fetcher.quit if fetcher.respond_to?(:quit)
      end
    rescue StandardError => e
      mutex.synchronize { failures << Failure.new(index: nil, url: nil, error: e) }
    end
  end

  threads.each(&:join)
  raise_for_failures(failures, results)

  results
end