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From "Steve Loughran (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HADOOP-9371) Define Semantics of FileSystem and FileContext more rigorously
Date Wed, 10 Jul 2013 18:33:52 GMT

     [ https://issues.apache.org/jira/browse/HADOOP-9371?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Steve Loughran updated HADOOP-9371:
-----------------------------------

    Attachment: HADOOP-9371-003.patch

Patch with the document in .apt format.

I'm trying to move away from must/may/should to a more formal definition -essentially using
set theory- I'd like feedback on this approach

# we need a good syntax, I've used Standard ML as the rough basis for this, but not perfectly.
# I'm not handling concurrency in the formal bits at all; that's a different level of formal
logics that I don't want to go near -even if I was confident I could use them.
# I'm working on the core operations: create, open, delete, & first.
# Rename is more complex than this, I need to go through all the relevant JIRAs as well as
the code.
# mkdir is surprising too -there are some inconsistencies between local & hdfs that I
need to understand better. It looks like hdfs always returns true "there is a directory",
while local returns true iff the directory was created.
# Permissions need to be defined as well, because of things like "What should the permissions
be up the dir tree when I call {{create(path)}} and its parents don't exist?"

Comments welcome
                
> Define Semantics of FileSystem and FileContext more rigorously
> --------------------------------------------------------------
>
>                 Key: HADOOP-9371
>                 URL: https://issues.apache.org/jira/browse/HADOOP-9371
>             Project: Hadoop Common
>          Issue Type: Sub-task
>          Components: fs
>    Affects Versions: 1.2.0, 3.0.0
>            Reporter: Steve Loughran
>            Assignee: Steve Loughran
>         Attachments: HADOOP-9361.2.patch, HADOOP-9361.patch, HADOOP-9371-003.patch, HadoopFilesystemContract.pdf
>
>   Original Estimate: 48h
>  Remaining Estimate: 48h
>
> The semantics of {{FileSystem}} and {{FileContext}} are not completely defined in terms
of 
> # core expectations of a filesystem
> # consistency requirements.
> # concurrency requirements.
> # minimum scale limits
> Furthermore, methods are not defined strictly enough in terms of their outcomes and failure
modes.
> The requirements and method semantics should be defined more strictly.

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