Ruby Net::HTTP - following 301 redirects - ruby

Question

My users submit urls (to mixes on mixcloud.com) and my app uses them to perform web requests.
A good url returns a 200 status code:
uri = URI.parse("http://www.mixcloud.com/ErolAlkan/hard-summer-mix/")
request = Net::HTTP.get_response(uri)(
#<Net::HTTPOK 200 OK readbody=true>
But if you forget the trailing slash then our otherwise good url returns a 301:
uri = "http://www.mixcloud.com/ErolAlkan/hard-summer-mix"
#<Net::HTTPMovedPermanently 301 MOVED PERMANENTLY readbody=true>
The same thing happens with 404's:
# bad path returns a 404
"http://www.mixcloud.com/bad/path/"
# bad path minus trailing slash returns a 301
"http://www.mixcloud.com/bad/path"
How can I 'drill down' into the 301 to see if it takes us on to a valid resource or an error page?
Is there a tool that provides a comprehensive overview of the rules that a particular domain might apply to their urls?

Answer 1

301 redirects are fairly common if you do not type the URL exactly as the web server expects it. They happen much more frequently than you'd think, you just don't normally ever notice them while browsing because the browser does all that automatically for you.
Two alternatives come to mind:
1: Use open-uri
open-uri handles redirects automatically. So all you'd need to do is:
require 'open-uri'
...
response = open('http://xyz...').read
If you have trouble redirecting between HTTP and HTTPS, then have a look here for a solution:
Ruby open-uri redirect forbidden
2: Handle redirects with Net::HTTP
def get_response_with_redirect(uri)
r = Net::HTTP.get_response(uri)
if r.code == "301"
r = Net::HTTP.get_response(URI.parse(r['location']))
end
r
end
If you want to be even smarter you could try to add or remove missing backslashes to the URL when you get a 404 response. You could do that by creating a method like get_response_smart which handles this URL fiddling in addition to the redirects.

Answer 2

I can't figure out how to comment on the accepted answer (this question might be closed), but I should note that r.header is now obsolete, so r.header['location'] should be replaced by r['location'] (per https://stackoverflow.com/a/6934503/1084675 )

Answer 3

rest-client follows the redirections for GET and HEAD requests without any additional configuration. It works very nice.
for result codes between 200 and 207, a RestClient::Response will be returned
for result codes 301, 302 or 307, the redirection will be followed if the request is a GET or a HEAD
for result code 303, the redirection will be followed and the request transformed into a GET
example of usage:
require 'rest-client'
RestClient.get 'http://example.com/resource'
The rest-client README also gives an example of following redirects with POST requests:
begin
RestClient.post('http://example.com/redirect', 'body')
rescue RestClient::MovedPermanently,
RestClient::Found,
RestClient::TemporaryRedirect => err
err.response.follow_redirection
end

Answer 4

Here is the code I came up with (derived from different examples) which will bail out if there are too many redirects (note that ensure_success is optional):
require "net/http"
require "uri"
class Net::HTTPResponse
def ensure_success
unless kind_of? Net::HTTPSuccess
warn "Request failed with HTTP #{#code}"
each_header do |h,v|
warn "#{h} => #{v}"
end
abort
end
end
end
def do_request(uri_string)
response = nil
tries = 0
loop do
uri = URI.parse(uri_string)
http = Net::HTTP.new(uri.host, uri.port)
request = Net::HTTP::Get.new(uri.request_uri)
response = http.request(request)
uri_string = response['location'] if response['location']
unless response.kind_of? Net::HTTPRedirection
response.ensure_success
break
end
if tries == 10
puts "Timing out after 10 tries"
break
end
tries += 1
end
response
end

Answer 5

Not sure if anyone is looking for this exact solution, but if you are trying to download an image http/https and store it to a variable
require 'open_uri_redirections'
require 'net/https'
web_contents = open('file_url_goes_here', :ssl_verify_mode => OpenSSL::SSL::VERIFY_NONE, :allow_redirections => :all) {|f| f.read }
puts web_contents