In my simple test, I have below code: SocketAddress socketAddress = new InetSocketAddress(hostAddressString, hostPortNumber);
Java documentation mentions that this class performs DNS lookups and maintains the DNS cache. I turned the cache off using Java system property "networkaddress.cache.ttl=0". When this line is executed, Java does a DNS lookup and DNS returns two IPs. Please see attached network capture. The InetSocketAddress class provides only one method to get the IP address back and to work with MINA, an instance of this class is provided. Now the fact that one IP went down is not reflected in DNS so even though you force DNS lookup, it will return two IPs. The InetSocketAddress. getAddress() returns one of these IPs and there is no guarantee that it would not give me the IP which went down. Thanks Suhas On Wed, Dec 19, 2012 at 11:03 AM, Jean-Yves Linet <[email protected]>wrote: > Well I don't know how it could be possible for Java to do a DNS lookup and > receive more than one IP. Is this kind of request included in DNS protocol > ?? If not it is not a Java limitation, it is just not possible to do. > In your case you could insert two domain name in your client app or you > could add your own load balancing protocol. > BTW did you try to lookup your DNS server with a non java application and > see what you get ? > > > > > 2012/12/19 Suhas Sutar <[email protected]> > > > After little more testing, I have concluded that it is not MINA issue. To > > open a connection to target server, I use below code with MINA: > > > > ====================================== > > ExecutorService ioExecutor = Executors.newCachedThreadPool(); > > IoConnector ioConnector = new SocketConnector(Runtime.getRuntime() > > .availableProcessors() > > + 1, ioExecutor); > > SocketAddress socketAddress = new InetSocketAddress(hostAddressString, > > hostPortNumber); > > ConnectFuture future = ioConnector.connect(socketAddress); > > ====================================== > > > > The InetSocketAddress class internally does a DNS lookup and maintains a > > cache of the IP addresses. But it seems that there is no way to retrieve > > all the IP addresses associated with a host name. The > > method InetSocketAddress.getAddress() returns only one IP address and > even > > though one of the IPs is unavailable, it would not cycle through the next > > one. I even turned off the DNS caching using Java system property > > "networkaddress.cache.ttl=0". > > > > Again, it is not caching issue in my opinion. Even though I want to > handle > > it in the application code, the Java APIs does not provide me a way to > know > > that there are multiple IP addresses for a given host. > > > > I am not sure how application developers are handling this situation. > > > > > > > > On Wed, Dec 19, 2012 at 6:14 AM, Emmanuel Lécharny <[email protected] > > >wrote: > > > > > Le 12/19/12 11:15 AM, Jean-Yves Linet a écrit : > > > > Hi, > > > > Well your problem can have multiple explanations : > > > > Do you remove the down host IP from the DNS list ? Otherwise DNS > server > > > > will continue to use it. > > > > DNS resolution can be cached somewhere. (see networkaddress.cache in > > Java > > > > properties) > > > > I doubt that this could be a MINA issue. > > > I was about to do the exact same answer. > > > > > > > > > > > > -- > > > Regards, > > > Cordialement, > > > Emmanuel Lécharny > > > www.iktek.com > > > > > > > > >
