I had the problem that if the network connection is really bad the server sometimes does not accept more connections. "Really bad" means that a simple ping event sent via thrift could take 15 seconds.
Having this issue for nearly 2 years now I could finally figure it out:
There is no timeout when the socket receives data. After a connection is established and the socket object is created, the connection can drop which yields to the socket blocking forever.
I added a timeout in the TSocket accept function which makes the socket throw a resource not available error after 30 seconds:
client, addr = self.handle.accept()
– added timeout of 30.0 seconds
client.setsockopt(socket.SOL_SOCKET, socket.SO_RCVTIMEO, struct.pack('LL', 30, 0))
result = TSocket()
Gives this error:
buff = self.handle.recv(sz)
error: [Errno 11] Resource temporarily unavailable
I also tried using python socket's settimeout() function which does not work. Only setting the receive timeout times out dropped connections.
This bug does not appear on stable connections. However, I have 4 devices that are connected via WiFi and my ThreadedServer gets stuck about 4-5 times a day. The ThreadedServer has 5 threads, thus all 5 sockets get stuck all the time...
FYI here is the strace of the stuck socket:
[pid 2698] futex(0x7faf50000d80, FUTEX_WAIT_PRIVATE, 0, NULL <unfinished ...>
[pid 2697] read(4, <unfinished ...>
[pid 2693] accept(7,
, ) = 6
[pid 2693] recvfrom(6,