[jira] [Commented] (HDFS-7665) Add definition of truncate preconditions/postconditions to filesystem specification

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

    [ https://issues.apache.org/jira/browse/HDFS-7665?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14290352#comment-14290352 ] 

Konstantin Shvachko commented on HDFS-7665:
-------------------------------------------

Steve, could you mention where exactly the specifications should be added.
I understand we need to add truncate operation to HDFS documentation here:
- http://hadoop.apache.org/docs/current/hadoop-project-dist/hadoop-common/FileSystemShell.html
- http://hadoop.apache.org/docs/current/hadoop-project-dist/hadoop-common/filesystem/filesystem.html

I guess you meant something else.

> Add definition of truncate preconditions/postconditions to filesystem specification
> -----------------------------------------------------------------------------------
>
>                 Key: HDFS-7665
>                 URL: https://issues.apache.org/jira/browse/HDFS-7665
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>          Components: documentation
>    Affects Versions: 3.0.0
>            Reporter: Steve Loughran
>             Fix For: 3.0.0
>
>
> With the addition of a major new feature to filesystems, the filesystem specification in hadoop-common/site is now out of sync. 
> This means that
> # there's no strict specification of what it should do
> # you can't derive tests from that specification
> # other people trying to implement the API will have to infer what to do from the HDFS source
> # there's no way to decide whether or not the HDFS implementation does what it is intended.
> # without matching tests against the raw local FS, differences between the HDFS impl and the Posix standard one won't be caught until it is potentially too late to fix.
> The operation should be relatively easy to define (after a truncate, the files bytes [0...len-1] must equal the original bytes, length(file)==len, etc)
> The truncate tests already written could then be pulled up into contract tests which any filesystem implementation can run against.



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