[HADOOP-1910] Extra checks in DFS.create() are not necessary.

• Type: Bug
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 0.14.1
• Fix Version/s: 0.15.0
• Assignee: Raghu Angadi
• Reporter: Raghu Angadi
• Created: 17/Sep/07 21:02
• Updated: 08/Jul/09 16:42
• Resolved: 26/Sep/07 18:29

Description

DistributedFileSystem.create(path) like this :

  public FSDataOutputStream create(Path f, boolean overwrite,
    int bufferSize, short replication, long blockSize,
    Progressable progress) throws IOException {
    if (exists(f) && !overwrite) {
      throw new IOException("File already exists:"+f);
    }
    Path parent = f.getParent();
    if (parent != null && !exists(parent) && !mkdirs(parent)) {
      throw new IOException("Mkdirs failed to create " + parent);
    }

    return new FSDataOutputStream( dfs.create(getPathName(f), overwrite, 
                                              replication, blockSize, 
                                              progress, bufferSize, ticket));
  }

This has overhead of 2-3 RPCs to namenode for every create(). The first exists() is not required because overwrite flag is passed to Namenode. The second exists() and mkdirs() is not required since create() already does this.