[finefs] New ideas: data expiration and plugins

[amaury]

I am thinking about two new improvements.

1. Data expiration
As written on the FineFS' project page, it could be used to store
cache data (like Memcache). But for this kind of usage, we need to set
up a validity duration for each data set.

So, the putData() and putFile() methods of the FineFS object will get
an optional parameter, wich takes the expiration duration in seconds.
Any further read operation done after the expiration will fail (as for
a reading on an unknown file).

2. Plugins
I am working on a lightweight non-relational database management
system, built upon FineFS. This system will need a deep integration
with the storage layer (FineFS' role), and this could be done using a
plugin mechanism.

It would be possible to declare plugins for some operation types.
Then, a plugin would be called each time a new file is created on a
machine, and/or each time a file is deleted, and/or each time a file
is read.

I'm pretty sure these mechanisms could be useful for many
applications. What do you think about them?