Not detecting a dropped connection

[ghost]

When the graphite server drops the connection it's not detected. Returning if not buf forces the exception from unpack.

def read_all(self, sock, n):
"""
Read n bytes from a stream
"""
data = ''
while n > 0:
buf = sock.recv(n)
if not buf:
return data
n -= len(buf)
data += buf
return data