Module: UmlautHttp

Included in:
Blacklight, GoogleBookSearch, Scopus, Worldcat
Defined in:
lib/umlaut_http.rb

Overview

Helper module for service adaptors making HTTP requests, as most do. Eventually this may include some HTTP request wrapper methods that set timeout appropriately, and perhaps even do some HTTP level cacheing.

Right now, just a helper method for generating headers for proxy-like requests.

Instance Method Summary collapse

Instance Method Details

#http_fetch(uri, options = {}) ⇒ Object

Right now the main thing this will do for you is (sort of, stupidly) maintain cookies given in redirects. Later it might do other cooler things. Returns a Net::HTTP::Response



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# File 'lib/umlaut_http.rb', line 72

def http_fetch(uri, options = {})
  options[:max_redirects] ||= 8
  options[:redirects_left] ||= options[:max_redirects]
  options[:raise_on_http_error_code] = true unless options.has_key?(:raise_on_http_error_code)

    uri = URI.parse(uri) unless uri.kind_of?(URI)
    http = Net::HTTP.new(uri.host, uri.port)
    http.use_ssl = true if uri.scheme == "https"
    headers = options[:headers] || {}
    headers["Cookie"] = options[:cookies] if options[:cookies]

    response = http.request_get(uri.request_uri, headers)
          
    if ( response.kind_of?(Net::HTTPRedirection))
       raise ArgumentError, "HTTP redirect too deep (max #{options[:max_redirects]})" if options[:redirects_left] <= 0

       options[:cookies] = response['Set-Cookie']
       
       options[:redirects_left] = options[:redirects_left] - 1
       
       return http_fetch(response['location'], options)
    else
      response.value if options[:raise_on_http_error_code]        
      return response
    end
end

#proxy_like_headers(request, host = nil) ⇒ Object

Generate headers for a proxy-like request, so a service adaptor can make a request to a foreign service that appears to be HTTP-proxied from the original client browser, instead of just originating from Umlaut. This in some cases helps get around service traffic limiting, and in general is more honest and gives the service some good information about the actual end user.

Not generally neccesary for accessing actual APIs, but sometimes useful for screen scraping, or for an API intended to be client-side JS only.

request is an Umlaut Request, which has in it information about original client request and ip. host is optional, and is the ultimate destination you will be sending the proxy-like request to. if supplied, a not entirely honest X-Forwarded-Host header will be added.



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# File 'lib/umlaut_http.rb', line 27

def proxy_like_headers(request, host = nil)
  orig_env = request.http_env
  if (request.http_env.nil? || ! request.http_env.kind_of?(Hash))
    Rails.logger.warn("proxy_like_headers: orig_env arg is missing, proxy-like headers will be flawed. request id: #{request.id}. ")
    orig_env = {}
  end

  header = {}

  # Bunch of headers we proxy as-is from the original client request,
  # supplying reasonable defaults. 
  
  header["User-Agent"] = orig_env['HTTP_USER_AGENT'] || 'Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9) Gecko/2008061015 Firefox/3.0'
  header['Accept'] = orig_env['HTTP_ACCEPT'] || 'text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8'
  header['Accept-Language'] = orig_env['HTTP_ACCEPT_LANGUAGE'] || 'en-us,en;q=0.5'
  header['Accept-Encoding'] = orig_env['HTTP_ACCEPT_ENCODING'] || ''
  header["Accept-Charset"] = orig_env['HTTP_ACCEPT_CHARSET'] || 'UTF-8,*'

  # Set referrer to be, well, an Umlaut page, like the one we are
  # currently generating would be best. That is, the resolve link. 
  
  header["Referer"] = "http://#{orig_env['HTTP_HOST']}#{orig_env['REQUEST_URI']}"

  # Proxy X-Forwarded headers. 

  # The original Client's ip, most important and honest. Look for
  # and add on to any existing x-forwarded-for, if neccesary, as per
  # x-forwarded-for convention. 

  header['X-Forwarded-For'] =  (orig_env['HTTP_X_FORWARDED_FOR']) ?
     (orig_env['HTTP_X_FORWARDED_FOR'].to_s + ', ' + request.client_ip_addr.to_s) :
     request.client_ip_addr.to_s
     
  #Theoretically the original host requested by the client in the Host HTTP request header. We're disembling a bit.  
  header['X-Forwarded-Host'] = host if host
  # The proxy server: That is, Umlaut, us. 
  header['X-Forwarded-Server'] = orig_env['SERVER_NAME'] || '' 
  
  return header
  
end