If you're interested in the semantics of FileSystem operations, have a
look a HADOOP-9371[0]
Depending on what you're trying to do, the thread-safety of a particular
FS implementation in a single JVM instance may not be as important as
the semantics you get across JVM instances.
Best,
matt
[0] https://issues.apache.org/jira/browse/HADOOP-9371
On 04/01/2013 06:17 PM, Arpit Agarwal wrote:
Hi John,
DistributedFileSystem is intended to be thread-safe, true to its name.
Metadata operations are handled by the NameNode server which
synchronizes concurrent client requests via locks (you can look at the
FSNameSystem class).
Some discussion on the thread-safety aspects of HDFS:
http://storageconference.org/2010/Papers/MSST/Shvachko.pdf
-Arpit
On Sun, Mar 31, 2013 at 11:52 AM, Ted Yu <[email protected]
<mailto:[email protected]>> wrote:
If you look at DistributedFileSystem source code, you would see that
it calls the DFSClient field member for most of the actions.
Requests to Namenode are then made through ClientProtocol.
An hdfs committer would be able to give you affirmative answer.
On Sun, Mar 31, 2013 at 11:27 AM, John Lilley
<[email protected] <mailto:[email protected]>> wrote:
*From:*Ted Yu [mailto:[email protected]
<mailto:[email protected]>]
*Subject:* Re: Is FileSystem thread-safe?____
>>FileSystem is an abstract class, what concrete class are you
using (DistributedFileSystem, etc) ? ____
Good point. I am calling FileSystem.get(URI uri, Configuration
conf) with an URI like “hdfs://server:port/…” on a remote
server, so I assume it is creating a DistributedFileSystem.
However I am not finding any documentation discussing its
thread-safety (or lack thereof), perhaps you can point me to it?____
Thanks, john____
