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https://issues.apache.org/jira/browse/HADOOP-7472?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13070607#comment-13070607
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Kihwal Lee commented on HADOOP-7472:
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Description of the manual testing performed.
Set up:
* Namenode runs on "testhost".
* "testhost" is defined in /etc/hosts. A script switches the IP address of
testhost, between 127.0.0.1 and the real IP address of the box.
* hostname set to testhost.
* nscd or avahi not running.
Procedure:
* Start HDFS.
* Put files.
* Call a script to perform FS operations using fs shell.
* Kill NN. => operations block. RPC.client retry. This is the conn refused
case, so they give up quick. The timeout case (node or switch shutdown) will
last about 15 min until returning exception.
* Before clients giving up, switch the IP address and start namenode.
Result:
* The outstanding calls (in invoke()) get InvalidRPCAddressException.
* The clients that were blocked at the RPC initialization unblock and work.
* The clients that retry on exception will recover on their own.
> 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
> Fix For: 0.20.205.0
>
> Attachments: addr_change_dfs-1.patch.txt, addr_change_dfs.patch.txt
>
>
> 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.
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