Why does PDFKit/wkhtmltopdf hang but renders PDF as expected when Rails app is killed?

问题

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 -V it 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 my application.rb file.
included gem 'pdfkit' in my Gemfile and installed it with Bundler
set the .pdf mime-type in my mime_types.rb initializer with Mime::Type.register_alias "application/pdf", :pdf
added config.threadsafe! to config/environments/development.rb for multiple threads so asset pipeline doesn't conflict with PDF engine
tested wkhtmltopdf http://www.google.com google.pdf and 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

回答1:

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

回答2:

Try the last version. The easy way install on MacOS:

brew install Caskroom/cask/wkhtmltopdf

回答3:

The fix by scarver2 worked for me as advertised. But I needed a more recent version of wkhtmltopdf. Since the homebrew version still seems outdated (it still hangs on the command line), and since there isn't a recent precompiled binary available, I used the os x build script to compile one myself:

$ git clone git@github.com:wkhtmltopdf/wkhtmltopdf.git
$ cd wkhtmltopdf
$ ./build_osx.sh     # i'm running 10.9.2
$ bin/wkhtmltopdf --version                                                                                  
Name:
  wkhtmltopdf 0.12.1-72a9f2066fe9ffd162dec007a4d9b6a5cd63b670
$ curl www.example.com | bin/wkhtmltopdf - test.pdf  # render pdf of example.com
$ open test.pdf   # to confirm pdf

I'm using pdfkit 0.6.2 with Rails 3.2.17. I put the binary in /vendor and, in a pdfkit initializer, pointed to it with config.wkhtmltopdf. So far, so good.

回答4:

I got the same issue. It works when I added: 'config.threadsafe!' in application.rb as the answer in the stack. Hope this help.

回答5:

Mine was also hanging and opening the wkhtmltopdf icon in the dock.

I actually found the problem for me was I only had 1 unicorn worker process running. Once I added more than 1 it worked fine.

I'm running wkhtmltopdf 0.9.9 on OS X with pdfkit 0.6.2

回答6:

Exact same symptoms but using WickedPdf currently. At this point, I believe the issue lies with wkhtmltopdf as well.

Unfortunately, neither of the recommendations I've been able to find in Stack/Google worked for me. Instead, I needed to combine several suggestions, including some found in this post.

Solution was:

brew uninstall wkhtmltopdf
find and delete any copies of wkhtmltopdf in /usr/bin
comment WickedPdf.config line in config/initializers
add config.threadsafe! to development.rb
remove middleware and allow 'show' action of main controller to handle pdf requests (may not be necessary)
add wkhtmltopdf-binary to gemfile
bundle
restart server
You may also need to add Mime::Type.register_alias "application/pdf", :pdf to config/initializers/mime_types.rb (for me, this causes 'warning: already initialized constant PDF')

My set-up was: Mac OSX Mountain Lion with Rails 3.2.1, Webrick, Postgres and wkhtmltopdf-binary (0.9.9.1).

回答7:

Try editing config/initializer/pdfkit.rb in the following way:

PDFKit.configure do |config|

config.wkhtmltopdf = Rails.root.join('bin', 'wkhtmltopdf-i386').to_s

config.default_options = {

  :encoding=>"UTF-8",
  :page_size=>"A4",
  :margin_top=>"0.25in",
  :margin_right=>"0.1in",
  :margin_bottom=>"0.25in",
  :margin_left=>"0.1in",
  :disable_smart_shrinking=> false
}
end

来源：https://stackoverflow.com/questions/12517640/why-does-pdfkit-wkhtmltopdf-hang-but-renders-pdf-as-expected-when-rails-app-is-k

标签

ruby-on-rails-3

pdf

osx-mountain-lion

wkhtmltopdf

pdfkit