Hi Erik, You can also do this one-by-one (aka, a rolling reboot). Shut it down, wait for it to be recognized as dead, then bring it back up with a new hostname. It will take a much longer time, but you won't have any decrease in availability, just some minor decrease in capacity.
This is useful in sites like ours where we have 24/7 usage and try to avoid any unnecessary downtime. Brian On Aug 10, 2010, at 8:42 AM, Allen Wittenauer wrote: > > On Aug 10, 2010, at 3:51 AM, Erik Forsberg wrote: > >> Hi! >> >> Due to network reconfigurations, I need to change the hostnames of some >> of my worker nodes, i.e. the nodes running tasktracker and datanode. I >> need to do this to make my hostname naming schema actually concur with >> the network setup. >> >> Are there any problems doing this? It seems HDFS identifies things >> using some kind of hostname-independent UID, so I guess it should >> recover from one machine going down and then appear again under another >> hostname? > > > The name node metadata only matches blocks #s to files. The data node to > block part is determined at run time. So it is perfectly safe and legal to: > > a) bring grid down > b) rename everything > c) fix config files > d) bring grid up > > Don't forget to change your network topology script, slaves, and dfs.hosts as > necessary. If fsck complains about topology violations, use setrep to > increase then setrep to decrease the violated files.
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