[jira] Commented: (HADOOP-1283) Eliminate internal UTF8 to String and vice versa conversions in the name-node.

["Konstantin Shvachko (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HADOOP-1283?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12502469 ] 

Konstantin Shvachko commented on HADOOP-1283:
---------------------------------------------

UTF8 elimination proposal.
# Protocols (ClientProtocol, DatanodeProtocol) - no change - parameters will remain Strings
# RPC - no change - will convert Strings into UTF8s, send, and convert them back to Strings on the server.
# Internal name-node method parameters will be Strings.
# Internal name-node data structures should use BytesWritable instead of UTF8 and String.
# EditsLog and FSImage entries will use BytesWritable instead of UTF8 for serialization into files.

> Eliminate internal UTF8 to String and vice versa conversions in the name-node.
> ------------------------------------------------------------------------------
>
>                 Key: HADOOP-1283
>                 URL: https://issues.apache.org/jira/browse/HADOOP-1283
>             Project: Hadoop
>          Issue Type: Improvement
>          Components: dfs
>    Affects Versions: 0.12.0
>            Reporter: Konstantin Shvachko
>
> We have internal conversions of those two types inside name-node code. One example:
> NameNode.complete(String src, String clientName)
> then it calls
> FSNamesystem.completeFile(new UTF8(src), new UTF8(clientName));
> which in turn finally calls
> FSDirectory.addNode(path.toString(), newNode )
> and in another place
> FSDirectory.getNode(src.toString())
> So we have several conversions of the same parameter back and forth during computation.
> We should keep the parameter type consistent within different methods.
> The question is, which type should be used: String or Text.
> From previous discussions I remember that Text is more efficient in space and time for non ASCII
> data. Here we mostly deal with file names and network addresses, which are ASCII.
> Does it make sense to use Text in this case?
> UTF8 is also used as a key in two maps: pendingCreates and leases.
> This should be replaced too.

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