1#
2# We use a background thread for sharing fds on Unix, and for sharing sockets on
3# Windows.
4#
5# A client which wants to pickle a resource registers it with the resource
6# sharer and gets an identifier in return.  The unpickling process will connect
7# to the resource sharer, sends the identifier and its pid, and then receives
8# the resource.
9#
10
11import os
12import signal
13import socket
14import sys
15import threading
16
17from . import process
18from .context import reduction
19from . import util
20
21__all__ = ['stop']
22
23
24if sys.platform == 'win32':
25    __all__ += ['DupSocket']
26
27    class DupSocket(object):
28        '''Picklable wrapper for a socket.'''
29        def __init__(self, sock):
30            new_sock = sock.dup()
31            def send(conn, pid):
32                share = new_sock.share(pid)
33                conn.send_bytes(share)
34            self._id = _resource_sharer.register(send, new_sock.close)
35
36        def detach(self):
37            '''Get the socket.  This should only be called once.'''
38            with _resource_sharer.get_connection(self._id) as conn:
39                share = conn.recv_bytes()
40                return socket.fromshare(share)
41
42else:
43    __all__ += ['DupFd']
44
45    class DupFd(object):
46        '''Wrapper for fd which can be used at any time.'''
47        def __init__(self, fd):
48            new_fd = os.dup(fd)
49            def send(conn, pid):
50                reduction.send_handle(conn, new_fd, pid)
51            def close():
52                os.close(new_fd)
53            self._id = _resource_sharer.register(send, close)
54
55        def detach(self):
56            '''Get the fd.  This should only be called once.'''
57            with _resource_sharer.get_connection(self._id) as conn:
58                return reduction.recv_handle(conn)
59
60
61class _ResourceSharer(object):
62    '''Manager for resources using background thread.'''
63    def __init__(self):
64        self._key = 0
65        self._cache = {}
66        self._lock = threading.Lock()
67        self._listener = None
68        self._address = None
69        self._thread = None
70        util.register_after_fork(self, _ResourceSharer._afterfork)
71
72    def register(self, send, close):
73        '''Register resource, returning an identifier.'''
74        with self._lock:
75            if self._address is None:
76                self._start()
77            self._key += 1
78            self._cache[self._key] = (send, close)
79            return (self._address, self._key)
80
81    @staticmethod
82    def get_connection(ident):
83        '''Return connection from which to receive identified resource.'''
84        from .connection import Client
85        address, key = ident
86        c = Client(address, authkey=process.current_process().authkey)
87        c.send((key, os.getpid()))
88        return c
89
90    def stop(self, timeout=None):
91        '''Stop the background thread and clear registered resources.'''
92        from .connection import Client
93        with self._lock:
94            if self._address is not None:
95                c = Client(self._address,
96                           authkey=process.current_process().authkey)
97                c.send(None)
98                c.close()
99                self._thread.join(timeout)
100                if self._thread.is_alive():
101                    util.sub_warning('_ResourceSharer thread did '
102                                     'not stop when asked')
103                self._listener.close()
104                self._thread = None
105                self._address = None
106                self._listener = None
107                for key, (send, close) in self._cache.items():
108                    close()
109                self._cache.clear()
110
111    def _afterfork(self):
112        for key, (send, close) in self._cache.items():
113            close()
114        self._cache.clear()
115        self._lock._at_fork_reinit()
116        if self._listener is not None:
117            self._listener.close()
118        self._listener = None
119        self._address = None
120        self._thread = None
121
122    def _start(self):
123        from .connection import Listener
124        assert self._listener is None, "Already have Listener"
125        util.debug('starting listener and thread for sending handles')
126        self._listener = Listener(authkey=process.current_process().authkey)
127        self._address = self._listener.address
128        t = threading.Thread(target=self._serve)
129        t.daemon = True
130        t.start()
131        self._thread = t
132
133    def _serve(self):
134        if hasattr(signal, 'pthread_sigmask'):
135            signal.pthread_sigmask(signal.SIG_BLOCK, signal.valid_signals())
136        while 1:
137            try:
138                with self._listener.accept() as conn:
139                    msg = conn.recv()
140                    if msg is None:
141                        break
142                    key, destination_pid = msg
143                    send, close = self._cache.pop(key)
144                    try:
145                        send(conn, destination_pid)
146                    finally:
147                        close()
148            except:
149                if not util.is_exiting():
150                    sys.excepthook(*sys.exc_info())
151
152
153_resource_sharer = _ResourceSharer()
154stop = _resource_sharer.stop
155