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From "zhihai xu (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HADOOP-12443) LocalDirAllocator shouldn't accept pathStr parameter with scheme or authority.
Date Sun, 27 Sep 2015 23:01:04 GMT
zhihai xu created HADOOP-12443:
----------------------------------

             Summary: LocalDirAllocator shouldn't accept pathStr parameter with scheme or
authority.
                 Key: HADOOP-12443
                 URL: https://issues.apache.org/jira/browse/HADOOP-12443
             Project: Hadoop Common
          Issue Type: Improvement
          Components: fs
            Reporter: zhihai xu
            Assignee: zhihai xu


{{LocalDirAllocator}} shouldn't accept {{pathStr}} parameter with scheme or authority.
Currently {{LocalDirAllocator}} accepts {{pathStr}} with scheme or authority, When {{pathStr}}
with scheme or authority is passed to {{getLocalPathForWrite}}, it will bypass {{localDirs}}
to use {{pathStr}} directly , then the return Path will be independent with {{localDirs}}.
The reason is the following:
{{LocalDirAllocator}} will use {{new Path(new Path(localDirs[dirNumLastAccessed]), pathStr)}}
as the return Path.
The constructor code for {{Path}} is
{code}
  public Path(Path parent, Path child) {
    // Add a slash to parent's path so resolution is compatible with URI's
    URI parentUri = parent.uri;
    String parentPath = parentUri.getPath();
    if (!(parentPath.equals("/") || parentPath.isEmpty())) {
      try {
        parentUri = new URI(parentUri.getScheme(), parentUri.getAuthority(),
                      parentUri.getPath()+"/", null, parentUri.getFragment());
      } catch (URISyntaxException e) {
        throw new IllegalArgumentException(e);
      }
    }
    URI resolved = parentUri.resolve(child.uri);
    initialize(resolved.getScheme(), resolved.getAuthority(),
               resolved.getPath(), resolved.getFragment());
  }
{code}
The above {{Path}} constructor code will call {{URI#resolve}} to merge the parent path with
child path.
{code}
    private static URI resolve(URI base, URI child) {
        // check if child if opaque first so that NPE is thrown
        // if child is null.
        if (child.isOpaque() || base.isOpaque())
            return child;

        // 5.2 (2): Reference to current document (lone fragment)
        if ((child.scheme == null) && (child.authority == null)
            && child.path.equals("") && (child.fragment != null)
            && (child.query == null)) {
            if ((base.fragment != null)
                && child.fragment.equals(base.fragment)) {
                return base;
            }
            URI ru = new URI();
            ru.scheme = base.scheme;
            ru.authority = base.authority;
            ru.userInfo = base.userInfo;
            ru.host = base.host;
            ru.port = base.port;
            ru.path = base.path;
            ru.fragment = child.fragment;
            ru.query = base.query;
            return ru;
        }

        // 5.2 (3): Child is absolute
        if (child.scheme != null)
            return child;

        URI ru = new URI();             // Resolved URI
        ru.scheme = base.scheme;
        ru.query = child.query;
        ru.fragment = child.fragment;

        // 5.2 (4): Authority
        if (child.authority == null) {
            ru.authority = base.authority;
            ru.host = base.host;
            ru.userInfo = base.userInfo;
            ru.port = base.port;

            String cp = (child.path == null) ? "" : child.path;
            if ((cp.length() > 0) && (cp.charAt(0) == '/')) {
                // 5.2 (5): Child path is absolute
                ru.path = child.path;
            } else {
                // 5.2 (6): Resolve relative path
                ru.path = resolvePath(base.path, cp, base.isAbsolute());
            }
        } else {
            ru.authority = child.authority;
            ru.host = child.host;
            ru.userInfo = child.userInfo;
            ru.host = child.host;
            ru.port = child.port;
            ru.path = child.path;
        }

        // 5.2 (7): Recombine (nothing to do here)
        return ru;
    }
{code}
You can see if the child's uri has scheme or authority, it won't use anything from parent's
uri.
This will hide the issue for user. For example, user passed file:///build/test/temp as {{pathStr}}
parameter to {{getLocalPathForWrite}}.
Later on user may run into very strange problem: /build/test/temp directory is full because
return path is not from {{localDirs}}. This makes the issue very difficult for user to debug.
So it will be better to reject {{pathStr}} parameter with scheme or authority.




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