[
https://issues.apache.org/jira/browse/HADOOP-4952?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12752136#action_12752136
]
Todd Lipcon commented on HADOOP-4952:
-------------------------------------
bq. Given that the latter is available for anyone convinced that they need to
pass a set of CreateOpts though several layers, the single-object CreateOpts
seems to offer few advantages other than keystrokes and the impossibility of
duplicate entries in the varargs.
My issue is that the multi-argument form pushes the handling of defaults down
into the FS implementation, whereas it was my understanding from this patch
that the defaults should be handled by FileContext (or another FS-independent
class). If there is a single-object CreateOpts, it could either have the
defaults preset by its constructor, or have getters that returned defaults when
the variables had not been set.
bq. Todd: for readability, would you mind trying to compose feedback in a less
verbose format?
Yes, I apologize for having such a lengthy/detail-oriented review of a
preliminary patch. Given the 0.21 freeze is coming up soon, and my next two
weeks are pretty busy, I wanted to get all my comments out there now in case I
didn't have time to look again. For future reviews I'll try to more cleanly
delineate the detail-oriented things from more important macro issues. A proper
code review tool hooked up to JIRA would be invaluable here.
> Improved files system interface for the application writer.
> -----------------------------------------------------------
>
> Key: HADOOP-4952
> URL: https://issues.apache.org/jira/browse/HADOOP-4952
> Project: Hadoop Common
> Issue Type: Improvement
> Affects Versions: 0.21.0
> Reporter: Sanjay Radia
> Assignee: Sanjay Radia
> Attachments: FileContext3.patch, FileContext5.patch,
> FileContext6.patch, FileContext7.patch, FileContext9.patch, Files.java,
> Files.java, FilesContext1.patch, FilesContext2.patch
>
>
> Currently the FIleSystem interface serves two purposes:
> - an application writer's interface for using the Hadoop file system
> - a file system implementer's interface (e.g. hdfs, local file system, kfs,
> etc)
> This Jira proposes that we provide a simpler interfaces for the application
> writer and leave the FilsSystem interface for the implementer of a
> filesystem.
> - Filesystem interface has a confusing set of methods for the application
> writer
> - We could make it easier to take advantage of the URI file naming
> ** Current approach is to get FileSystem instance by supplying the URI and
> then access that name space. It is consistent for the FileSystem instance to
> not accept URIs for other schemes, but we can do better.
> ** The special copyFromLocalFIle can be generalized as a copyFile where the
> src or target can be generalized to any URI, including the local one.
> ** The proposed scheme (below) simplifies this.
> - The client side config can be simplified.
> ** New config() by default uses the default config. Since this is the common
> usage pattern, one should not need to always pass the config as a parameter
> when accessing the file system.
> -
> ** It does not handle multiple file systems too well. Today a site.xml is
> derived from a single Hadoop cluster. This does not make sense for multiple
> Hadoop clusters which may have different defaults.
> ** Further one should need very little to configure the client side:
> *** Default files system.
> *** Block size
> *** Replication factor
> *** Scheme to class mapping
> ** It should be possible to take Blocksize and replication factors defaults
> from the target file system, rather then the client size config. I am not
> suggesting we don't allow setting client side defaults, but most clients do
> not care and would find it simpler to take the defaults for their systems
> from the target file system.
--
This message is automatically generated by JIRA.
-
You can reply to this email to add a comment to the issue online.
