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Introduction to Ruby using eventmachine to add file download function to HTTP server

高洛峰

Mar 04, 2017 pm 04:13 PM

Idea:

Use ruby eventmachine and em-http-server gem to complete a simple HttpServer that provides file download function;
Use EM's FileStreamer to send files asynchronously. File first assembles the header and then calls FileStreamer.

Code:

require &#39;rubygems&#39;
require &#39;eventmachine&#39;
require &#39;em-http-server&#39;
 
class HTTPHandler < EM::HttpServer::Server
 attr_accessor :filename, :filesize, :path
 
 def process_http_request
  #send file async
  if @http_request_method.to_s =~ /GET/ && @http_request_uri.to_s.end_with?(filename)
   send_data "HTTP/1.1 200 OK\n"
   send_data "Server: XiaoMi\n"
   send_data "Connection: Keep-Alive\n"
   send_data "Keep-Alive: timeout=15\n"
   send_data "Content-Type: application/octet-stream\n"
   send_data "Content-Disposition: filename=&#39;#{filename}&#39;\n"
   send_data "Content-Length: #{filesize}\n"
   send_data "\n"
 
   streamer = EventMachine::FileStreamer.new(self, path)
   streamer.callback {
    # file was sent successfully
    close_connection_after_writing
   }
  else
   response = EM::DelegatedHttpResponse.new(self)
   response.status = 200
   response.content_type &#39;text/html&#39;
   response.content = "Package HttpServer<br>usage: wget http://www.php.cn/:port/#{filename}"
   response.send_response
  end
 end
 
end
 
EM::run do
 path = &#39;/tmp/aaa.tar.gz&#39;
 EM::start_server("0.0.0.0", 8080, HTTPHandler) do |conn|
  conn.filename = File.basename(path)
  conn.filesize = File.size(path)
  conn.path = path
 end
end

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PS: About eventmachine installation error
On windows Installing eventmachine always reports an error:

Building native extensions. This could take a while...
ERROR: Error installing eventmachine:
    ERROR: Failed to build gem native extension.

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or another one:

ERROR: Error installing ruby-debug:
      The &#39;linecache&#39; native gem requires installed build tools.
   
  Please update your PATH to include build tools or download the DevKit
  from &#39;http://rubyinstaller.org/downloads&#39; and follow the instructions
  at &#39;http://github.com/oneclick/rubyinstaller/wiki/Development-Kit&#39;

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After a long search on Google, I found 2 solutions:

1. Use a lower version of eventmachine

This prompt keeps coming, and there is another one below Difficult mistakes, they are all C compilation errors. Later I found two methods on the Internet
(1)

gem install eventmachine-win32

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This seems to be a lower version installed.
(2)gem install

 eventmachine --pre

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This seems to install beta 1.0.0.

2. Upgrade devkit

After looking at it, there is no specific solution mentioned above, but two possible reasons for the problem are given:
(1) No C compilation environment
(2) There are spaces in the path
Look at the error log above and find that it may be a problem with the compilation environment. So I looked for it.
My ruby was installed using one-click installer, and the version is 1.8.6-p398.
On the addon page of rubyinstaller, I found DevKit.
Looked at the description of DevKit:

//Sometimes you just want RubyGems to build that cool native,
//C-based extension without squawking.
//Who's your buddy? DevKit!
Looks like this is what I need.

The reason for the error is that when installing eventmachine, build tools are required, but they are not available in the system. The error message also provides a solution:
(1) Go to http://rubyinstaller.org/downloads/ to download the dev kit – DevKit-tdm-32-4.5.1-20101214-1400-sfx. exe
(2) Follow http://github.com/oneclick/rubyinstaller/wiki/Development-Kit/ to install dev kit

The main installation steps are as follows:
If it has already been installed in the original system For the old version of dev kit, delete it
Download the dev kit mentioned above
Unzip the downloaded file to the specified directory, such as c:/devkit. (Note: The directory cannot have spaces)
Run ruby dk.rb, and then follow the prompts to run ruby dk.rb init and ruby dk.rb install to enhance ruby
Can run

gem install rdiscount –platform=ruby

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to test whether it is successful.
Follow the installation steps and complete the installation of DevKit, which is very simple.

Then, install eventmachine again:

gem install eventmachine

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