FB will want:

   Give me new $fh for a given key.  (which is for a domain)
   Give me a path to a file to sendfile.  (from a key)

Perl <-> mogilefs interface:

   1) request new fid/path for a given key

        < CREATE_OPEN domain=test&key=foo%27+sdf&class=<class_ident>
        > ERR <errcode> <errstring>
              nodb
              foo
        > OK <arg_length> fid=234&devid=342&path=/blah/foo/sdff
        > ERR invalid_domain "Provided domain is not registered"

        'key' may be optional, in which an anonymous file (not in
          namespace is returned).  essentially a temp/spool file.

        optional request key:  'multi_dest=1' signals that server should
        reply not with keys "devid" and "path" but instead with:

             dev_count=3
             devid_1=10
             devid_2=17
             devid_3=26
             path_1=http://host1:7500/dev10/...
             path_2=http://host2:7500/dev17/...
             path_3=http://host3:7500/dev26/...

        .. that way if the server unknowingly gave the client a down storage node,
        the client can immediately try somewhere else.

   2) close fid (and the devid, path that was written to)

        < CREATE_CLOSE domain=test&key=foo&fid=343&devid=34&path=/sdf/sf/sdf

        -- fid and devid are totally opaque strings.  server just uses
           them to verify the path and key.

        -- it's possible two clients did a CREATE_OPEN on same key, got
           diff fids (123 and 124), then 123 closes first and loses, since
           key is now owned by 124, not 123.

        > ERR expiredfid URL_encode("Expired file: another connection created the same file between your open and close")
        > ERR bogus_devid "Devid doesn't correspond to path"
        > ERR invalid_domain "Provided domain is not registered"


   3) give string path to a given domainid+key

        < GET_PATHS domain=test&key=FOOBAR
        
	> OK <arg_length> paths=<n>&path1=.....&path2=.....

           (client should prefer them in order given)

    4) delete a key

        < DELETE domain=test&key=sdfsdfsdfsdf
        > OK 0

        
    5) get a list of domains and classes for them

        < GET_DOMAINS
        > OK domains=1&domain1=test&domain1classes=1&domain1class1name=alt&domain1class1mindevcount=2

        -- this is a two level hash; there are N domains (taken from the
           key 'domains') and their names are stored in 'domainX' where X is
           in the range 1..N.

        -- each domain has N classes (taken from 'domainXclasses');
           each class has two keys in the form of 'domainXclassYname' and
           'domainXclassYmindevcount' where Y is in the range of 1..N.

           
    6) create a new domain on the fly
    
        < CREATE_DOMAIN domain=mynewdomain
        > OK domain=mynewdomain

        -- returns the domain you just created as the only response value


    7) create a new class

        < CREATE_CLASS domain=mynewdomain&class=theclass&mindevcount=2
        > OK domain=mynewdomain&class=theclass&mindevcount=2

        -- creates a new class under the domain you specify named 'class' with
           the minimum device replication count of 'mindevcount'


    8) updates a class's minimum device replica count

        < UPDATE_CLASS domain=mynewdomain&class=theclass&mindevcount=3
        > OK domain=mynewdomain&class=theclass&mindevcount=3

        -- same as create_class except it overwrites the mindevcount of the class
           you are specifying.  useful if you want to change the replica count
           for a class.