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From "Eli Collins (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-5438) Merge FileSystem.create and FileSystem.append
Date Tue, 01 Jun 2010 19:52:39 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-5438?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12874200#action_12874200
] 

Eli Collins commented on HADOOP-5438:
-------------------------------------

HDFS-609 (create with the append flag doesn't work) is marked as a blocker for 21. Since the
combined create/append API does not work and there's still some debate as to what the right
API is it seems like the right thing to do here is revert this change for 21 (and on trunk)
and figure out the right API before we put it in an official release. Reasonable?

> Merge FileSystem.create and FileSystem.append
> ---------------------------------------------
>
>                 Key: HADOOP-5438
>                 URL: https://issues.apache.org/jira/browse/HADOOP-5438
>             Project: Hadoop Common
>          Issue Type: Improvement
>          Components: fs
>            Reporter: He Yongqiang
>            Assignee: He Yongqiang
>             Fix For: 0.21.0
>
>         Attachments: Hadoop-5438(2009-04-06).patch, Hadoop-5438-2009-03-30.patch, Hadoop-5438-2009-03-31-2.patch,
Hadoop-5438-2009-03-31.patch, Hadoop-5438-2009-05-10.patch, Hadoop-5438-2009-05-15.patch,
Hadoop-5438-2009-05-19.patch, Hadoop-5438-2009-05-5.patch
>
>
> Currently, when a user wants to modify a file, the user first calls exists() to know
if this file is already there. And then uses create() or append() according to whether the
file exists or not.
> the code looks like:
> {code}
> FSDataOutputStream out_1 = null;
> if (fs.exists(path_1))
>    out_1 = fs.append(path_1);
> else
>    out_1 = fs.create(path_1);
> {code}
> . On the performace side,It involes two RPCs. On the easy-of-use side, it is not very
convient in contrast to the traditional open interface.
> It will more complicate if there is a overwrite parameter specified. I donot know whether
there is a bug about 'overwrite' in 0.19, some times it takes a long time for overwrite creates
to reture. So i make the write file code with overwrite param works like:
> {code}
> boolean exists = fs.exists(name);
> if (overwrite) {
>     if (exists)
>        fs.delete(name, true);
>      this.out = fs.create(name, overwrite, bufferSize, replication,
> 				    blockSize, progress);
>      this.currentRowID = 0;
>  } else {
>    if (!exists)
> 	this.out = fs.create(name, overwrite, bufferSize,
> 					replication, blockSize, progress);
>    else
> 	this.out = fs.append(name, bufferSize, progress);
> {code}
> Some code statements there are really redundant and not needed, especialy with the delete().
But without deleting first, the overwrite takes a long time to reture.
> BTW, i will create another issue about the overwrite problem. If it is not a bug at all
or a duplicate, someone please close it.

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