Suresh, You are correct I did not explain myself very well. If one of the name nodes has hardware failure. In order to avoid updating the configs for every single service that talks to HDFS you have to make sure the replacement box appears to the network to be exactly the same as the original. This is not impossible as you mentioned.
The more common case when this is problematic is upgrading clusters from non-HA to HA, or adding in new HA clusters, because there is no existing IP address/config to be copied. Every time this happens all existing services must have new configs pushed to be able to talk to the new/updated HDFS. This includes Gateways, RM, Compute Nodes, Oozie Servers, etc. Again, this is not that big of a deal for a small setup, but for a large setup it can be painful. --Bobby On 11/5/13 4:57 PM, "Suresh Srinivas" <sur...@hortonworks.com> wrote: >On Tue, Nov 5, 2013 at 6:57 AM, Bobby Evans <ev...@yahoo-inc.com> wrote: > >> But that does present a problem if you have to change the DNS address of >> one of the HA namenodes. > > >Not sure what you mean by this? Do you mean hostname of one of the >namenode >changes? >If so, why is this is not a problem for single namenode deployment?. How >do >applications >addressing a namenode in a different cluster handle the change? > > >> It forces you to update the config on all other >> clusters that want to talk to it. If you only have a few clusters that >>is >> probably not a big deal, but it can be problematic if you have many >> different clusters that talk to each other. >> >> --Bobby >> >> On 11/4/13 4:15 PM, "lohit" <lohit.vijayar...@gmail.com> wrote: >> >> >Thanks Suresh! >> > >> > >> >2013/11/4 Suresh Srinivas <sur...@hortonworks.com> >> > >> >> Lohit, >> >> >> >> The option you have enumerated at the end is the current way to set >>up >> >> multi cluster >> >> environment. That is, all the client side configurations will include >> >>the >> >> following: >> >> - Logical service names (either for federation or HA) >> >> - The corresponding physical namenode addresses information >> >> >> >> For simpler management, one could use xml include to include an xml >> >> document >> >> that defines all the namespaces and namenodes. >> >> >> >> Regards, >> >> Suresh >> >> >> >> >> >> On Mon, Nov 4, 2013 at 2:02 PM, lohit <lohit.vijayar...@gmail.com> >> >>wrote: >> >> >> >> > Hello Devs, >> >> > >> >> > With hadoop 1.0 when there was single namespace. One could access >>any >> >> HDFS >> >> > cluster using any other hadoop config. Something like this >> >> > >> >> > hadoop --config /path/to/hadoop-cluster1 >>hdfs://hadoop-cluster2:8020/ >> >> > >> >> > Since NameNode host and port were passed directly as part of URI, >>if >> >>hdfs >> >> > client version matched, one could talk to different clusters >>without >> >> > needing to have access to cluster specific configuration. >> >> > >> >> > With Hadoop 2.0 or HA mode, we only specify logical name for >>namenode >> >>and >> >> > rely on hdfs-site.xml to resolve logical name to two underlying >> >>namenode >> >> > hosts. >> >> > >> >> > So, you cannot do something like >> >> > hadoop --config /path/to/hadoop-cluster1 >> >> > hdfs://hadoop-cluster2-logicalname/ >> >> > >> >> > since /path/to/hadoop-cluster1/hdfs-site.xml do not have >>information >> >> about >> >> > hadoop-cluster2-logicalname's namenodes. >> >> > >> >> > >> >> > One option is to add hadoop-cluster2-logicalname's namednodes to >> >> > /path/to/hadoop-cluster1/hdfs-site.xml. But with many clusters, >>this >> >> > becomes problem. >> >> > Is there any other cleaner approach to solving this? >> >> > >> >> > -- >> >> > Have a Nice Day! >> >> > Lohit >> >> > >> >> >> >> >> >> >> >> -- >> >> http://hortonworks.com/download/ >> >> >> >> -- >> >> CONFIDENTIALITY NOTICE >> >> NOTICE: This message is intended for the use of the individual or >> >>entity to >> >> which it is addressed and may contain information that is >>confidential, >> >> privileged and exempt from disclosure under applicable law. If the >> >>reader >> >> of this message is not the intended recipient, you are hereby >>notified >> >>that >> >> any printing, copying, dissemination, distribution, disclosure or >> >> forwarding of this communication is strictly prohibited. If you have >> >> received this communication in error, please contact the sender >> >>immediately >> >> and delete it from your system. Thank You. >> >> >> > >> > >> > >> >-- >> >Have a Nice Day! >> >Lohit >> >> > > >-- >http://hortonworks.com/download/ > >-- >CONFIDENTIALITY NOTICE >NOTICE: This message is intended for the use of the individual or entity >to >which it is addressed and may contain information that is confidential, >privileged and exempt from disclosure under applicable law. If the reader >of this message is not the intended recipient, you are hereby notified >that >any printing, copying, dissemination, distribution, disclosure or >forwarding of this communication is strictly prohibited. If you have >received this communication in error, please contact the sender >immediately >and delete it from your system. Thank You.
