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https://issues.apache.org/jira/browse/HDFS-14118?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16754659#comment-16754659
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Chao Sun commented on HDFS-14118:
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Thanks [~fengnanli]. Patch v5 looks better. Some (most minor) comments:
- Instead of {{resolve-service}}, how about {{resolver.impl}} or
{{resolve-service.impl}}? the {{RESOLVE_SERVICE}} should also be postfixed with
{{_KEY}}.
- Remove unused imports in AbstractNNFailoverProxyProvider and
ConfiguredFailoverProxyProvider.
- Can we add some docs for the DNSDomainNameResolver class?
- In TestConfiguredFailoverProxyProvider, the {{ns3nn1SocketAddress}} and
{{ns3nn2SocketAddress}} can be local variable to
{{testResolveDomainNameUsingDNS}}. Also the variable {{ns3DomainNameAddress}}
is not used.
- Instead of the long string
"org.apache.hadoop.hdfs.server.namenode.ha.TestConfiguredFailoverProxyProvider$MockDomainNameResolver",
you can just use {{MockDomainNameResolver.class.getName()}}.
- In AbstractNNFailoverProxyProvider, please add an empty line before the
first {{@param}} Java doc. Also remove {{@throws}} or explain when it will be
thrown.
- In AbstractNNFailoverProxyProvider, can we also log the resolver class name?
- In AbstractNNFailoverProxyProvider, the {{createDomainNameResolver}} does
not need to be public it seems.
> Use DNS to resolve Namenodes and Routers
> ----------------------------------------
>
> Key: HDFS-14118
> URL: https://issues.apache.org/jira/browse/HDFS-14118
> Project: Hadoop HDFS
> Issue Type: New Feature
> Reporter: Fengnan Li
> Assignee: Fengnan Li
> Priority: Major
> Attachments: DNS testing log, HDFS-14118.001.patch,
> HDFS-14118.002.patch, HDFS-14118.003.patch, HDFS-14118.004.patch,
> HDFS-14118.005.patch, HDFS-14118.patch
>
>
> Clients will need to know about routers to talk to the HDFS cluster
> (obviously), and having routers updating (adding/removing) will have to make
> every client change, which is a painful process.
> DNS can be used here to resolve the single domain name clients knows to a
> list of routers in the current config. However, DNS won't be able to consider
> only resolving to the working router based on certain health thresholds.
> There are some ways about how this can be solved. One way is to have a
> separate script to regularly check the status of the router and update the
> DNS records if a router fails the health thresholds. In this way, security
> might be carefully considered for this way. Another way is to have the client
> do the normal connecting/failover after they get the list of routers, which
> requires the change of current failover proxy provider.
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