Hi,
I was trying to set up a distributed cache architecture with JCS, the
memory cache and the disk auxiliary were working just fine but I could
not set up the remote auxiliary properly.
After some investigation I suspect that the reason the client could not
communicate with the server properly has to do with the JCS code relying
on InetAddress.getLocalHost() method call which returns ambiguous
results on Linux systems. (I later found a bug report about this at
http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=4665037 ).
E.g.: client looking up an IPv6 enabled Fedora Core 6 server:
"looking up server
//192.168.6.28:1102/org.apache.jcs.auxiliary.remote.behavior.IRemoteCach
eService"
org.apache.jcs.auxiliary.remote.RemoteCacheManager 107:Naming.lookup(
"//192.168.6.28:1102/org.apache.jcs.auxiliary.remote.behavior.IRemoteCac
heService" );
"server found"
"remote service = RemoteCacheServer_Stub ...
endpoint:[0:0:0:0:0:0:0:1:1103](remote),objID:[7c19e... etc."
at the same time the same client looking up another also IPv6 enabled
Fedora Core 6 server:
"looking up server
//192.168.10.59:1102/org.apache.jcs.auxiliary.remote.behavior.IRemoteCac
heService"
org.apache.jcs.auxiliary.remote.RemoteCacheManager 107:Naming.lookup(
"//192.168.10.59:1102/org.apache.jcs.auxiliary.remote.behavior.IRemoteCa
cheService" );
"server found"
"remote service = RemoteCacheServer_Stub ...
endpoint:[192:168.10.59:1103](remote),objID:[806c6c..."
A possible workaround could be to replace the
InetAddress.getLocalHost() calls with a method similar to the snippet
below to return the IP address that enables RMI calls from remote
machines:
public static String getLocalHostAddress() throws UnknownHostException{
return getLocalHostLANAddress().toString();
}
public static InetAddress getLocalHostLANAddress() throws
UnknownHostException {
try {
for(Enumeration ifaces = NetworkInterface.getNetworkInterfaces();
ifaces.hasMoreElements();){
NetworkInterface iface = (NetworkInterface)ifaces.nextElement();
for(Enumeration inetAddrs = iface.getInetAddresses();
inetAddrs.hasMoreElements();){
InetAddress inetAddr = (InetAddress)inetAddrs.nextElement();
if (!inetAddr.isLoopbackAddress() && inetAddr.isSiteLocalAddress())
{
return
InetAddress.getByAddress(InetAddress.getLocalHost().getHostName(),
inetAddr.getAddress());
}
}
}
}
catch (Exception e) {
throw new UnknownHostException("Failed to determine LAN address: " +
e);
}
throw new UnknownHostException("Failed to locate LAN address.");
}
I could bypass the problem by completely disabling IPv6 on our server
but for the future it might be beneficial to ensure JCS runs reliably on
Linux without a need to make such configuration.
If you think there are other ways to sort out this issue please let me
know.
Regards:
Zsolt
P.S.: Good luck with JCS - a very nice piece of work otherwise.
