From: Pat Maddox Date: 2005-04-03T05:19:36+09:00 Subject: Re: Handling Timeout::Error from TCPSocket All I'm trying to do is see if a connection can be made or not, in a specified amount of time. Here's the method I've written, would you mind telling me how I could improve upon it? def execute numtries = 0 while numtries < @retries + 1 puts "Trying to connect" numtries += 1 timeout(@timeoutval, StandardError) { socket = TCPSocket.new(@host, @port) rescue false if socket socket.close result = TestResult.new result.testId = @id result.status = TestResult::STATUS_SUCCEEDED return result end } rescue StandardError puts "Unable to connect" sleep @retryDelay if numtries < @retries + 1 end result = TestResult.new result.testId = @id result.status = TestResult::STATUS_FAILED result.info = "Unable to connect" return result end On Apr 2, 2005 1:09 PM, Sam Roberts wrote: > Quoting pergesu@gmail.com, on Sun, Apr 03, 2005 at 03:33:47AM +0900: > > > > I don't want to override the protocol's idea of a timeout - I'd like > > > > some means of specifying a timeout for the connection though. In > > Be clear that you ARE overriding the protocols idea of a timeout by > terminating the connect() before the stack has decided the peer cannot > be connected. > > > In Java: > > > > Socket s = new Socket(); > > s.connect(new InetSocketAddress(getHost(), port), timeout); > > > > I can specify a timeout value for the connection, as you see above. > > True enough, I was looking at the TCPSocket constructors, which don't > allow this. Note this didn't exist prior to JDK 1.4, its a recent hack, > true to Java's "everything plus the sink" philosophy it looks like. > > http://java.sun.com/features/2002/08/j2se-network.html > > I still find your "all the other languages" statement a little over the > top, JDK1.4 isn't a very large "all". > > Overriding the TCP protocol's timeouts in the application is > questionable practice. I'm not telling you how to write your app, you > might have good reasons to do this, so do it. I am saying that overeager > timeouts and retransmissions have been known to cause very hard to find > and fix bugs when applications that work fine on a local network or > machine mysteriously start timing out over dialup or WiFi links. > > > I don't see a way of doing that with the Ruby classes. I'm new to > > Ruby, so I really don't know - is there a way to do it? > > Yes, as I showed you; > > begin > Timeout.timeout(18) do > TCPSocket.new(... > end > rescue Timeout::Error > ... > end > > You would wrap this into a nice function if you wanted to do it a lot. > > Also, you may find that doing your connects in a seperate thread allows > you to not fiddle with the timeout, and still avoid your app blocking > if the network is slow or flaky. > > Have fun. > Sam > > > > > On Apr 2, 2005 11:14 AM, Sam Roberts wrote: > > > Quoting pergesu@gmail.com, on Sun, Apr 03, 2005 at 02:03:51AM +0900: > > > > every other language I've used, I can set a timeout value on the > > > > socket itself. It doesn't look like that's the case in Ruby. Is > > > > > > The C, perl, and Java networking APIS don't support timeouts on TCP > > > connect(), and the C/BSD sockets API is what most (all?) other languages > > > use internally. > > > > > > Out of curiosity, what are these languages? > > > > > > > there a method somewhere in the Socket classe heirarchy that lets me > > > > specify a timeout? > > > > > > > > According to timeout, you can set an Exception that gets thrown when > > > > it times out. I set that to StandardError, and just handle > > > > > > Not sure what you mean. You can make timeout raise errors other than > > > Timeout::Error, and catch them, but you don't do so in the example you > > > posted. > > > > > > > StandardError at the end. According to the docs, Timeout::Error can't > > > > be used with rescue because it doesn't inherit from StandardError. > > > > > > I assure you that Timeout::Error can be caught by rescue, as I showed, I > > > do it quite often and it works fine. > > > > > > > I'd still like some means of setting a timeout value for a socket > > > > connection. That's a pretty basic aspect of the protocol, there's no > > > > reason it shouldn't be in there. > > > > > > I see no evidence that user configurable timeouts on connect() are not > > > part of the TCP protocol. > > > > > > Cheers, > > > Sam > > > > > > > On Apr 2, 2005 9:37 AM, Sam Roberts wrote: > > > > > Quoting pergesu@gmail.com, on Sat, Apr 02, 2005 at 08:05:15PM +0900: > > > > > > I'm writing a little method that just tries to open a tcp socket > > > > > > connection, then closes it off. I'm using timeout to limit the amount > > > > > > of time it tries to connect (is there a better way?). If it times > > > > > > > > > > I have to wonder why you want to override the TCP protocols ideas of a > > > > > timeout. The protocol designers and implementors have a pretty good idea > > > > > of what the timeouts should be. If its not fast enough for you, you > > > > > probably want too much. Doing this will make your code flaky and > > > > > unreliable when the network isn't as fast as your local network. A good > > > > > text on network programming should explain this. If you are finding your > > > > > app is blocked, you can use ruby threads to do connections in the > > > > > background. > > > > > > > > > > That said, you can't catch exceptions like that, try: > > > > > > > > > > begin > > > > > Timeout::timeout(3) do > > > > > long running op > > > > > end > > > > > rescue Timeout::Error > > > > > p "hi" > > > > > end > > > > > > > > > > Sam > > > > > > > > > > > out, I just want to say that the connect failed. Despite catching the > > > > > > Timeout::Error (I think, anyway), I always get the Exception output. > > > > > > First, here's the method: > > > > > > > > > > > > def execute > > > > > > status = timeout(@timeoutval) { > > > > > > socket = TCPSocket.new(@host, @port) rescue false > > > > > > > > > > > > socket.close if socket > > > > > > return socket != false > > > > > > } rescue Timeout::Error > > > > > > > > > > > > return false > > > > > > end > > > > > > > > > > > > And now the output from my unit test: > > > > > > > > > > > > Started > > > > > > /usr/local/lib/ruby/1.8/timeout.rb:42:in `new': execution expired > > > > > > (Timeout::Error) > > > > > > from ./PortHostTest.rb:16:in `execute' > > > > > > from ./PortHostTest.rb:15:in `timeout' > > > > > > from /usr/local/lib/ruby/1.8/timeout.rb:55:in `timeout' > > > > > > from ./PortHostTest.rb:15:in `execute' > > > > > > from ./HostTest.rb:10:in `runTest' > > > > > > from ../tests/test_HostTest.rb:14:in `test_simple' > > > > > > from /usr/local/lib/ruby/1.8/test/unit/testcase.rb:70:in `__send__' > > > > > > from /usr/local/lib/ruby/1.8/test/unit/testcase.rb:70:in `run' > > > > > > ... 10 levels... > > > > > > from /usr/local/lib/ruby/1.8/test/unit/autorunner.rb:194:in `run' > > > > > > from /usr/local/lib/ruby/1.8/test/unit/autorunner.rb:14:in `run' > > > > > > from /usr/local/lib/ruby/1.8/test/unit.rb:285 > > > > > > from /usr/local/lib/ruby/1.8/test/unit.rb:283 > > > > > > > > > > > > > > > > > > > > > > > > > > > > > >