Now the whole GlusterFS fops is asynchrounous, and all socket operations are made in Nonblocking way.

all read/write operations on sockets should be ensured not to block. currently all read()s happen after poll(). But all write() (reply from fops) happen without check, which can possibly lead to blocking indefinitely.

all socket operations should happen with a poll() check for both write and read.

all FILE * operations should be changed and should use the transport api's being added (tracked by #17354) which uses socket fd directly.

the non-blocking write may involve implementing a write queue which is flushed after poll() indicates write-ready.

Over clogging of the write-queue should be ensured by not read()ing from a socket which has N write-queue entries. (do not process requests from a socket which has not accepted the previous replies)