how to test open-uri url exist before processing any data - ruby

Question

I'm trying to process content from a list of links using "open-uri" in ruby (1.8.6), but the bad thing happens when I'm getting an error when one link is broken or requires authentication:
open-uri.rb:277:in `open_http': 404 Not Found (OpenURI::HTTPError)
from C:/tools/Ruby/lib/ruby/1.8/open-uri.rb:616:in `buffer_open'
from C:/tools/Ruby/lib/ruby/1.8/open-uri.rb:164:in `open_loop'
from C:/tools/Ruby/lib/ruby/1.8/open-uri.rb:162:in `catch'
or
C:/tools/Ruby/lib/ruby/1.8/net/http.rb:560:in `initialize': getaddrinfo: no address associated with hostname. (SocketError)
from C:/tools/Ruby/lib/ruby/1.8/net/http.rb:560:in `open'
from C:/tools/Ruby/lib/ruby/1.8/net/http.rb:560:in `connect'
from C:/tools/Ruby/lib/ruby/1.8/timeout.rb:53:in `timeout'
or
C:/tools/Ruby/lib/ruby/1.8/net/protocol.rb:133:in `sysread': An existing connection was forcibly closed by the remote host. (Errno::ECONNRESET)
from C:/tools/Ruby/lib/ruby/1.8/net/protocol.rb:133:in `rbuf_fill'
from C:/tools/Ruby/lib/ruby/1.8/timeout.rb:62:in `timeout'
from C:/tools/Ruby/lib/ruby/1.8/timeout.rb:93:in `timeout'
is there a way to test the response (url) before processing any data?
the code is:
require 'open-uri'
smth.css.each do |item|
open('item[:name]', 'wb') do |file|
file << open('item[:href]').read
end
end
Many thanks

Answer 1

You could try something along the lines of
require 'open-uri'
smth.css.each do |item|
begin
open('item[:name]', 'wb') do |file|
file << open('item[:href]').read
end
rescue => e
case e
when OpenURI::HTTPError
# do something
when SocketError
# do something else
else
raise e
end
rescue SystemCallError => e
if e === Errno::ECONNRESET
# do something else
else
raise e
end
end
end
I don't know of any way of testing the connection without opening it and trying, so rescuing these errors would be the only way I can think of. The thing to be aware of is that OpenURI::HTTPError and SocketError are both subclasses of StandardError, whereas Errno::ECONNRESET is a subclass of SystemCallError. So rescue => e won't catch Errno::ECONNRESET.

Answer 2

I was able to solve this problem by using a conditional if/else statement to check the return value of the action for "failure":
def controller_action
url = "some_API"
response = open(url).read
data = JSON.parse(response)["data"]
if response["status"] == "failure"
redirect_to :action => "home"
else
do_something_else
end
end