In Ruby on Rails, After send_file method delete the file from server
Asked Answered
P

3

41

I am using following code for sending the file in Rails.

if File.exist?(file_path)
  send_file(file_path, type: 'text/excel') 
  File.delete(file_path)
end

In this I am trying to send the file and delete the file from server once it is been send successfully. But I am facing issue is, the delete operation is getting executed while sending is performing and due to that I don't see anything in browser.

So is there any way in Rails, once the send_file operation is completed delete the file from server.

Any help on this would be highly appreciated.

Thanks,
Chetan

Penetration answered 14/8, 2013 at 12:42 Comment(1)
I don't this is possible inside the request handler, and you will want a delayed job or similar mechanism to clean up, allowing enough time for the download to of completedNazarene
P
54

Because you're using send_file, Rails will pass the request along to your HTTP server (nginx, apache, etc. - See the Rails documentation on send_file regarding X-Sendfile headers). Because of this, when you try to delete the file, Rails doesn't know that it's still being used.

You can try using send_data instead, which will block until the data is sent, allowing your File.delete request to succeed. Keep in mind that send_data requires a data stream as its argument though, not a path, so you need to open the file first:

File.open(file_path, 'r') do |f|
  send_data f.read, type: "text/excel"
end
File.delete(file_path)

The other option would be a background job that periodically checks for temp files to delete.

Piraeus answered 14/8, 2013 at 12:51 Comment(3)
Also keep in mind that send_data will likely use more resources to send same content as send_file, but no need to obsess about the difference unless this will be a heavily-used feature of the site.Nazarene
@NeilSlater Yes, for a basic text file that generates quickly it shouldn't be a big deal. But for generating large/slow files, a send_file + background job solution would probably be better.Piraeus
Thanks Dylan for responding on this. Following worked for me: if File.exist?(file_path) File.open(file_path, 'rb') do |f| send_data f.read, type: "application/excel", filename: "file_name.xls" end endPenetration
M
7

If you are generating on the fly the file you are trying to send, a solution is to use the Tempfile class:

begin
  # The second argument is optional:
  temp_file = Tempfile.new(filename, temp_directory)

  # ... edit temp_file as needed.

  # By default, temp files are 0600,
  # so this line might be needed depending on your configuration:
  temp_file.chmod(0644)
  send_file temp_file
ensure
  temp_file.close
end

Contrary to what is indicated in this question, this works as expected (the file stays on the server long enough to be served, but ultimately gets deleted); this post seems to indicate this is due to updates in Rails 3.2.11, something I couldn’t verify.

Mallorca answered 19/4, 2014 at 3:52 Comment(3)
I'm pretty sure if you want to actually delete the tempfile, you need to do something like temp_file.unlinkTwoedged
@MichaelWu According to the documentation, TempFile#close with no parameter ends up calling #unlink automatically, "when the object is finalized". It worked as expected for me.Mallorca
I wouldn't count on this working 100% of the time. It will delete the file when the Tempfile is garbage collected, and there are no guarantees that this will happen before nginx/apache has opened the file. It depends on the internal implementation of send_file in Rails. send_data is a better alternative.Margueritamarguerite
M
4

This works for me! With send_data you can delete file before send.

file = File.open(Rails.root.join('public', 'uploads', filename), "rb")
contents = file.read
file.close

File.delete(filepath) if File.exist?(filepath)

send_data(contents, :filename => filename)
Mania answered 3/12, 2014 at 16:18 Comment(0)

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