Pass the front_len we need when pulling a message off a msgpool,
and WARN if it is greater than the pool's size.  Then try to
allocate a new message (to continue without failing).
Signed-off-by: NSage Weil <sage@newdream.net>

Defined a struct for the SUBSCRIBE_ACK, and use that to size
the msgpool.
Signed-off-by: NSage Weil <sage@newdream.net>

This avoids the fugly pass by reference and makes the code a bit easier
to read.
Signed-off-by: NSage Weil <sage@newdream.net>

This lets us extend the format more easily.
Signed-off-by: NSage Weil <sage@newdream.net>

The mon request headers now include session_mon information that must
be properly initialized.
Signed-off-by: NSage Weil <sage@newdream.net>

Be conservative: renew subscription once half the interval has expired.

Do not reuse sub expiration to control hunting.
Signed-off-by: NSage Weil <sage@newdream.net>

The monitor cluster is responsible for managing cluster membership
and state.  The monitor client handles what minimal interaction
the Ceph client has with it: checking for updated versions of the
MDS and OSD maps, getting statfs() information, and unmounting.
Signed-off-by: NSage Weil <sage@newdream.net>