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https://issues.apache.org/jira/browse/HADOOP-5438?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12680366#action_12680366
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he yongqiang commented on HADOOP-5438:
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I guess the open and create interfaces can leave there for compatibility, and
can we add a new interface for open? With the new open interface, all work can
be done with only one RPC. And the atomicity can be guaranteed at the server
side. That's great, since the atomicity can not be made at the client side.
The atomicity is a great point, thanks hong.
> Merge FileSystem.create and FileSystem.append
> ---------------------------------------------
>
> Key: HADOOP-5438
> URL: https://issues.apache.org/jira/browse/HADOOP-5438
> Project: Hadoop Core
> Issue Type: Improvement
> Reporter: he yongqiang
>
> 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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