[THRIFT-4080] Unix sockets can get stuck forever

• Type: Bug
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 0.10.0
• Component/s: Python - Library

Environment

Ubuntu 14.04

• Flags: Important
• Assignee: Unassigned
• Reporter: David Fankhauser
• Created: 09/Feb/17 10:32
• Updated: 01/Aug/19 00:52

Description

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:

def accept(self):
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()
result.setHandle(client)
return result

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,

{sa_family=AF_INET6, sin6_port=htons(39911), inet_pton(AF_INET6, "::ffff:46.125.249.41", &sin6_addr), sin6_flowinfo=0, sin6_scope_id=0}

, [28]) = 6
[pid 2693] recvfrom(6,