Doug Cutting a écrit :
Thomas FRIOL wrote:
I would like to know today why it is not possible to append datas
into an existing file (Path) or why the FSDataOutputStream must be
closed before the file is written to the DFS.
Those are the current semantics of the filesytem: a file is not
readable until it is closed, and files are write-once. This
considerably simplifies the implementation and supports the primary
intended uses for DFS. The simpler we keep DFS the easier it is to
make it reliable and scalable. At this point we are prioritizing
reliability and scalability over new features. Over time, when
reliability and scalability are sufficiently demonstrated, these
restrictions may be removed.
In fact, my problem is that I have a servlet which is regularly
writing datas into a file in the DFS. Today, if my JVM crashes, I
lose all my datas because my output stream is closed only when the
JVM stops itself.
You could periodically close the file and start writing a new file.
It's exactly what I am doing now, but there is still some datas that we
cannot ensure not to be lost due to a JVM crash.
DFS is currently primarily used to support large, offline, batch
computations. For example, a log of critical data with tight
transactional requirements is probably an inappropriate use of DFS at
this time. Again, this may change, but that's where we are now.
Ok thanks for your help.
Doug
