On Fri, 2008-04-04 at 14:54 -0400, Talpey, Thomas wrote: > At 02:41 PM 4/4/2008, Chuck Lever wrote: > >Use TCP instead of UDP to contact the local rpcbind daemon. If > >rpcbind isn't listening, the connection is refused immediately, and > >the RPC client can tell without waiting for a timeout. > > You can get a prompt error if you use UDP connected mode (call > connect() on the UDP socket). Any ICMP port unreachable will > flow back to an ECONNREFUSED error on the socket. This doesn't > occur for unconnected UDP endpoints. I hadn't realised that was a feature of connected UDP sockets, but that's a good point. > >We would have to create a new RPC_CLNT_CREATE_FOO flag that tells the > >client to fail an RPC immediately if the connection is refused (kind > >of like the old "one shot" flag). This shouldn't be the default > >behavior. > Sounds reasonable. But, a port unreachable error should generally > be a "hard" indication, since it does come from the remote host, > or a middlebox acting as its proxy. In other words, any reasonably > small number of retries would all receive the same response. This is > much like a TCP RST - not a transitory event. UDP errors such as > host unreachable or network down (which come from the infrastructure > not the server) should not of course be considered this way and > retry is appropriate. > > Bottom line, I think it might actually be a useful default. Why does > the client currently retry ECONNREFUSED for port resolution? The client currently doesn't retry in the case of a connection failing for a soft RPC request. For hard RPC requests then it _must_ retry the connection, but it does so using an exponential backoff rule. Note that the NFSv4.1 channel bindings will probably force us to change this... Cheers Trond -- Trond Myklebust Linux NFS client maintainer NetApp Trond.Myklebust@xxxxxxxxxx www.netapp.com -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
