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Suresh Srinivas commented on HADOOP-7472: ----------------------------------------- http://download.oracle.com/javase/6/docs/api/java/net/InetAddress.html _By default, when a security manager is installed, in order to protect against DNS spoofing attacks, the result of positive host name resolutions are cached forever. When a security manager is not installed, the default behavior is to cache entries for a finite (implementation dependent) period of time. The result of unsuccessful host name resolution is cached for a very short period of time (10 seconds) to improve performance._ In setups where security manage is not installed, the test program I wrote did pickup new ip address for a host in 15 minutes on Sun JDK. So re-resolving the address for such setup is still a viable solution. I am not sure how other implementations do. > RPC client should deal with the IP address changes > -------------------------------------------------- > > Key: HADOOP-7472 > URL: https://issues.apache.org/jira/browse/HADOOP-7472 > Project: Hadoop Common > Issue Type: Improvement > Components: ipc > Affects Versions: 0.20.205.0 > Reporter: Kihwal Lee > Assignee: Kihwal Lee > Priority: Minor > > The current RPC client implementation and the client-side callers assume that > the hostname-address mappings of servers never change. The resolved address > is stored in an immutable InetSocketAddress object above/outside RPC, and the > reconnect logic in the RPC Connection implementation also trusts the resolved > address that was passed down. > If the NN suffers a failure that requires migration, it may be started on a > different node with a different IP address. In this case, even if the > name-address mapping is updated in DNS, the cluster is stuck trying old > address until the whole cluster is restarted. > The RPC client-side should detect this situation and exit or try to recover. > Updating ConnectionId within the Client implementation may get the system > work for the moment, there always is a risk of the cached address:port become > connectable again unintentionally. The real solution will be notifying upper > layer of the address change so that they can re-resolve and retry or > re-architecture the system as discussed in HDFS-34. > For 0.20 lines, some type of compromise may be acceptable. For example, raise > a custom exception for some well-defined high-impact upper layer to do > re-resolve/retry, while other will have to restart. For TRUNK, the HA work > will most likely determine what needs to be done. So this Jira won't cover > the solutions for TRUNK. -- This message is automatically generated by JIRA. For more information on JIRA, see: http://www.atlassian.com/software/jira