pybind/ceph_daemon: use small chunk for recv

socket.recv(bufsize) accept signed int in python, so if
we want to load huge data (mds -> cache_dump is an instance)
from admin socket , an EOVERFLOW exception will be throw.

Walk around this by only get READ_CHUNK_SIZE(4096) bytes data each call.

Signed-off-by: Xiaoxi Chen <xiaoxchen@ebay.com>

src/pybind/ceph_daemon.py

@@ -21,6 +21,7 @@
 
 COUNTER = 0x8
 LONG_RUNNING_AVG = 0x4
+READ_CHUNK_SIZE = 4096
 
 
 def admin_socket(asok_path, cmd, format=''):
@@ -45,7 +46,10 @@ def do_sockio(path, cmd_bytes):
 
             got = 0
             while got < l:
-                bit = sock.recv(l - got)
+                # recv() receives signed int, i.e max 2GB
+                # walk around by request max READ_CHUNK_SIZE per call.
+                want = min(l - got, READ_CHUNK_SIZE)
+                bit = sock.recv(want)
                 sock_ret += bit
                 got += len(bit)