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https://issues.apache.org/jira/browse/HDFS-14118?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16774848#comment-16774848
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Yongjun Zhang commented on HDFS-14118:
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Thanks for the explanation and new rev [~fengnanli].
A few more comments:
# In hdfs-default.xml, remove the statement about "Random order should be ..."
for both dfs.client.failover.resolve-needed and
dfs.client.failover.resolver.impl, since this is already mentioned in the
description of dfs.client.failover.random.order.
# The description for dfs.client.failover.random.order can be improved to
provide some more details about when to enable random and when not to. For
example, for HA Namenodes, we may not need to enable; for ObserverNodes and RBF
routers, it may be helpful to enable because we want to spread the load. This
can be deferred to a new jira if you'd like.
# Create a new Jira to fix the relevant doc places as [~elgoiri] pointed out
[here |
https://issues.apache.org/jira/browse/HDFS-14118?focusedCommentId=16773396&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-16773396].
My +1 after that.
Thanks.
> 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 design doc_ Single domain name for
> clients - Google Docs-1.pdf, HDFS design doc_ Single domain name for clients
> - Google Docs.pdf, HDFS-14118.001.patch, HDFS-14118.002.patch,
> HDFS-14118.003.patch, HDFS-14118.004.patch, HDFS-14118.005.patch,
> HDFS-14118.006.patch, HDFS-14118.007.patch, HDFS-14118.008.patch,
> HDFS-14118.009.patch, HDFS-14118.010.patch, HDFS-14118.011.patch,
> HDFS-14118.012.patch, HDFS-14118.013.patch, HDFS-14118.014.patch,
> HDFS-14118.015.patch, HDFS-14118.016.patch, HDFS-14118.017.patch,
> HDFS-14118.018.patch, HDFS-14118.019.patch, HDFS-14118.020.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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