memcached: call socket.recv multiple times to get all stats

New versions of memcached have more stats, making it more likely that stats
data will go across packet boundaries.  Previously, this caused
the collector to crash on interpreting the resulting data, since some
stats lines would be truncated, and some stats would be missing
altogether.

This also explicitly closes the socket when finished, as well as sets a
timeout on reading from the socket so it won't hang around waiting
forever to receive data if something goes wrong.

Author: dellis23

src/collectors/memcached/memcached.py

@@ -87,13 +87,26 @@ def get_raw_stats(self, host, port):
             else:
                 sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
                 sock.connect((host, int(port)))
+
+            # give up after a reasonable amount of time
+            sock.settimeout(3)
+
             # request stats
             sock.send('stats\n')
-            # something big enough to get whatever is sent back
-            data = sock.recv(4096)
+
+            # stats can be sent across multiple packets, so make sure we've
+            # read up until the END marker
+            while True:
+                received = sock.recv(4096)
+                if not received:
+                    break
+                data += received
+                if data.endswith('END\r\n'):
+                    break
         except socket.error:
             self.log.exception('Failed to get stats from %s:%s',
                                host, port)
+        sock.close()
         return data
 
     def get_stats(self, host, port):