属性在背景时不会更新，但在内联运行时可以正常工作

Question

我正在写一个screen scraper，它从帖子中获取一个URL列表，然后访问这些URL并获取页面上所有链接的列表。然后，它访问所有链接（原始链接和从片段中），并获得一个图像列表。当我内联运行作业时，一切都很好（除了需要30秒才能完成，这是一个问题，因为响应API调用需要很长时间）。出于某种原因，当我使用相同的html" target="_blank">代码并使用后台工作程序运行它时，有两个URL永远不会更新为已完成。它始终是相同的2个URL。

更奇怪的是，我收到了错误信息

3 TID-ov9t89ido WARN: NoMethodError: undefined method `search' for #<Mechanize::File:0x007f9d86e77a40>

3 TID-ov9t89ido警告：/app/app/models/scraper。rb:16:inscrape\u images'/app/app/workers/image\u worker。rb:5:inperform'/app/vendor/bundle/ruby/2.2.0/gems/sidekiq-4.1.1/lib/sidekiq/processor。rb:151:inexecute_job'/app/vendor/bundle/ruby/2.2.0/gems/sidekiq-4.1.1/lib/sidekiq/processor。rb:133:inblock（2 levels）in process'/app/vendor/bundle/ruby/2.2.0/gems/sidekiq-4.1.1/lib/sidekiq/middleware/chain。rb:127:invoke'/app/vendor/bundle/ruby/2.2.0/gems/newrelic_rpm-3.12.1.298/lib/newrelic/agent/instrumentation/sidekiq中的块。rb:33:inblock-in-call'/app/vendor/bundle/ruby/2.2.0/gems/newrelic_rpm-3.12.1.298/lib/new_relic/agent/instrumentation/controller_instrumentation。rb:361:inperform_action_with_newrelic_trace'/app/vendor/bundle/ruby/2.2.0/gems/newrelic_rpm-3.12.1.298/lib/newrelic/agent/instrumentation/sidekiq。rb:29:incall'/app/vendor/bundle/ruby/2.2.0/gems/sidekiq-4.1.1/lib/sidekiq/middleware/chain。rb:129:invoke'/app/vendor/bundle/ruby/2.2.0/gems/sidekiq-4.1.1/lib/sidekiq/middleware/server/active_record中的块。rb:6:incall'/app/vendor/bundle/ruby/2.2.0/gems/sidekiq-4.1.1/lib/sidekiq/middleware/chain。rb:129:ininvoke'/app/vendor/bundle/ruby/2.2.0/gems/sidekiq-4.1.1/lib/sidekiq/middleware/server/retry_jobs中的block。rb:74:incall'/app/vendor/bundle/ruby/2.2.0/gems/sidekiq-4.1.1/lib/sidekiq/middleware/chain。rb:129:ininvoke'/app/vendor/bundle/ruby/2.2.0/gems/sidekiq-4.1.1/lib/sidekiq/middleware/server/logging中的block。rb:11:inblock-in-call'/app/vendor/bundle/ruby/2.2.0/gems/sidekiq-4.1.1/lib/sidekiq/logging。rb:31:inwith_context'/app/vendor/bundle/ruby/2.2.0/gems/sidekiq-4.1.1/lib/sidekiq/middleware/server/logging。rb:7:incall'/app/vendor/bundle/ruby/2.2.0/gems/sidekiq-4.1.1/lib/sidekiq/middleware/chain。rb:129:invoke'/app/vendor/bundle/ruby/2.2.0/gems/sidekiq-4.1.1/lib/sidekiq/middleware/chain中的块。rb:132：在中调用'/app/vendor/bundle/ruby/2.2.0/gems/sidekiq-4.1.1/lib/sidekiq/middleware/chain。rb:132:ininvoke'/app/vendor/bundle/ruby/2.2.0/gems/sidekiq-4.1.1/lib/sidekiq/processor。rb:128:inblock-in-process'/app/vendor/bundle/ruby/2.2.0/gems/sidekiq-4.1.1/lib/sidekiq/processor。rb:167:instats'/app/vendor/bundle/ruby/2.2.0/gems/sidekiq-4.1.1/lib/sidekiq/processor。rb:127:inprocess'/app/vendor/bundle/ruby/2.2.0/gems/sidekiq-4.1.1/lib/sidekiq/processor。rb:79:inprocess\u one'/app/vendor/bundle/ruby/2.2.0/gems/sidekiq-4.1.1/lib/sidekiq/processor。rb:67:inrun'/app/vendor/bundle/ruby/2.2.0/gems/sidekiq-4.1.1/lib/sidekiq/util。rb:16:inwatchdog'/app/vendor/bundle/ruby/2.2.0/gems/sidekiq-4.1.1/lib/sidekiq/util。rb:24:inblock in safe_thread'

这来自以下代码：

 def self.scrape_images(uri)
    page = get_page(uri)
    base_url = page.uri.to_s
    images = page.search('//img') || []
    qualify_images(uri, images).push(base_url)
  end

我看到Mechanize不是线程安全的，我认为这可能是我的问题，但我不认为当它适用于其他所有方面时，它会给我这个错误。任何帮助都将是光荣的，谢谢阅读。

Answer 1

我正在添加答案，因为我在搜索时没有找到答案。如果Mechanize访问内容类型的页面。它不返回页面对象，而是返回文件对象。在我的案例中，我用一个保护条款解决了这个问题：

return [] unless page.class == Mechanize::Page