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From "David Fankhauser (JIRA)" <j...@apache.org>
Subject [jira] [Created] (THRIFT-4080) Unix sockets can get stuck forever
Date Thu, 09 Feb 2017 10:32:41 GMT
David Fankhauser created THRIFT-4080:
----------------------------------------

             Summary: Unix sockets can get stuck forever
                 Key: THRIFT-4080
                 URL: https://issues.apache.org/jira/browse/THRIFT-4080
             Project: Thrift
          Issue Type: Bug
          Components: Python - Library
    Affects Versions: 0.10.0
         Environment: Ubuntu 14.04
            Reporter: David Fankhauser
            Priority: Critical


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, 



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