为什么 PDFKit/wkhtmltopdf 挂起但在 Rails 应用程序被终止时按预期呈现 PDF? [英] Why does PDFKit/wkhtmltopdf hang but renders PDF as expected when Rails app is killed?
问题描述
背景
在我看来，
Background
After reading around it seemed to me that Prawn is out and wkhtmltopdf is in. It also seems like the PDFKit and wicked_pdf gems for Rails are the new cool. So I found a screencast by Ryan on how to use PDFKit. I installed everything, tested wkhtmltopdf on the CLI with no problems, fiddled around with Rails settingsto run multiple processes so the asset pipeline works, and all seemed good, except I'm still stuck at the very end of the process (actually getting the PDF response from the server).
Question
When I request a .pdf version of my view (I'm using the PDFKit Middleware option) my browser just sits there waiting for a response, but as soon as I kill the Rails process the PDF I expected to get only then pops up in my browser window. What gives?
What I'm Using
- OS: OSX 10.8.1
- Rails: 3.2.8
- Ruby: 1.9.3
- wkhtmltopdf: 0.11.0_rc1 (although when I run
wkhtmltopdf -Vit says 0.10.0_rc2) - qt: 4.8.2
What I've Done
- used the PDFKit middleware by loading
config.middleware.use "PDFKit::Middleware"in myapplication.rbfile. - included
gem 'pdfkit'in my Gemfile and installed it with Bundler - set the
.pdfmime-type in mymime_types.rbinitializer withMime::Type.register_alias "application/pdf", :pdf - added
config.threadsafe!toconfig/environments/development.rbfor multiple threads so asset pipeline doesn't conflict with PDF engine - tested
wkhtmltopdf http://www.google.com google.pdfand it generated a PDF of the Google homepage as expected - tried swapping PDFKit for wicked_pdf and encountered the same problem (hanging, but when Rails process is killed the PDF renders as expected)
What it Looks Like
This is the regular html page rendered by Rails (I've blurred the client details):
This is the CLI output by Rails when I try to navigate to localhost:3000/some/path.pdf. (the app hangs while waiting for a response):
When I finally kill the Rails process with ctrl-c the PDF finally shows up in the browser as I expected to see it (CSS and HTML rendered properly, so assets seem to load fine):
Conclusions So Far
Swapping PDFKit for wicked_pdf and getting the same results seems to make me think the problem isn't with those libraries, but something to do with my development environment. But wkhtmltopdf runs fine off the command line, so that makes me think that it and QT are doing their job. The problem must be in Rails. Maybe I'm not configuring something properly?
Plea for Help
How do I determine what exactly the problem is and how do I fix it?
I'll love you if you can help me <3
Update
I've also tried using an alternative method of rendering the PDF (with .to_pdf) without the middleware option as follows (doing this I commented out config.middleware.use "PDFKit::Middleware" from my application.rb file):
respond_to do |format|
format.html
format.pdf do
html = '<html><body>This is a test.</body></html>'
@pdf = PDFKit.new(html)
send_data @pdf.to_pdf,
:filename => 'whatever.pdf',
:type => 'application/pdf',
:disposition => 'attachment'
end
end
The problem is with wkhtmltopdf itself, specifically, any version after 0.9.9. wkhtmltopdf hangs when run directly from the command-line.
Steps to correct:
brew uninstall wkhtmltopdf
cd /usr/local/Library/Formula/
git checkout 6e2d550 /usr/local/Library/Formula/wkhtmltopdf.rb
brew install wkhtmltopdf
Then verify the correct version is installed wkhtmltopdf --version which should yield wkhtmltopdf 0.9.9
Citations:
- https://github.com/mileszs/wicked_pdf/issues/110
- http://wearepandr.com/blog/article/homebrew-and-installing-old-package-versions#blog_nav
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