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.
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.
Doug
