Python selectors.EVENT_READ Examples

def _run(self):
        sock = self._socket
        selector = selectors.DefaultSelector()
        selector.register(sock, selectors.EVENT_READ)
        while sock.fileno() > 0:
            self.log.debug("Waiting for incoming connections ...")
            events = selector.select(timeout=1.0)
            if events:
                try:
                    conn, addr = sock.accept()
                except OSError as ex:
                    if ex.errno in (errno.EBADF, errno.EINVAL):
                        break
                    raise
                self.log.debug("... got connection %s from %s", conn, addr)
                handler = Handler(self, (conn, addr))
                t = threading.Thread(target=handler.run)
                t.setDaemon(True)
                t.start() 

def run(self):
        retry = True

        self.logger.info("Connecting to Socket")
        sel = selectors.DefaultSelector()
        conn = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        conn.setsockopt(
            socket.SOL_SOCKET, socket.SO_LINGER, struct.pack('ii', 1, 0))
        conn.setblocking(False)

        conn.connect_ex((self.ip, self.port))
        sel.register(conn, selectors.EVENT_READ, data=None)

        while retry:
            events = sel.select()
            for key, mask in events:
                retry = self.__handle_client__(key, mask, sel)

        sel.unregister(conn)
        if self.result['success']:
            conn.shutdown(socket.SHUT_RDWR)

        self.qresult.put(self.result)
        self.logger.info("Socket Closed") 

def _process_event(self, key, mask):
        """Selector has delivered us an event."""
        self._logger.debug('Processing event with key {} and mask {}'.format(key, mask))
        fileobj, (reader, writer) = key.fileobj, key.data
        if mask & selectors.EVENT_READ and reader is not None:
            if reader._cancelled:
                self.remove_reader(fileobj)
            else:
                self._logger.debug('Invoking reader callback: {}'.format(reader))
                reader._run()
        if mask & selectors.EVENT_WRITE and writer is not None:
            if writer._cancelled:
                self.remove_writer(fileobj)
            else:
                self._logger.debug('Invoking writer callback: {}'.format(writer))
                writer._run() 

def service_connection(key, mask):
    sock = key.fileobj
    data = key.data
    if mask & selectors.EVENT_READ:
        recv_data = sock.recv(BUFFER_SIZE)
        if recv_data:
            print('Received {} from connection {}'.format(repr(recv_data), data.connid))
            data.recv_total += len(recv_data)
        if not recv_data or data.recv_total == data.msg_total:
            print('Closing connection', data.connid)
            selector.unregister(sock)
            sock.close()
    if mask & selectors.EVENT_WRITE:
        if not data.outb and data.messages:
            data.outb = data.messages.pop(0).encode()
        if data.outb:
            print('Sending {} to connection {}'.format(repr(data.outb), data.connid))
            sent = sock.send(data.outb)
            sock.shutdown(socket.SHUT_WR)
            data.outb = data.outb[sent:] 

def serve_forever(self, poll_interval=0.5):
        """Handle one request at a time until shutdown.

        Polls for shutdown every poll_interval seconds. Ignores
        self.timeout. If you need to do periodic tasks, do them in
        another thread.
        """
        self.__is_shut_down.clear()
        try:
            # XXX: Consider using another file descriptor or connecting to the
            # socket to wake this up instead of polling. Polling reduces our
            # responsiveness to a shutdown request and wastes cpu at all other
            # times.
            with _ServerSelector() as selector:
                selector.register(self, selectors.EVENT_READ)

                while not self.__shutdown_request:
                    ready = selector.select(poll_interval)
                    if ready:
                        self._handle_request_noblock()

                    self.service_actions()
        finally:
            self.__shutdown_request = False
            self.__is_shut_down.set() 

def test_register(self):
        s = self.SELECTOR()
        self.addCleanup(s.close)

        rd, wr = self.make_socketpair()

        key = s.register(rd, selectors.EVENT_READ, "data")
        self.assertIsInstance(key, selectors.SelectorKey)
        self.assertEqual(key.fileobj, rd)
        self.assertEqual(key.fd, rd.fileno())
        self.assertEqual(key.events, selectors.EVENT_READ)
        self.assertEqual(key.data, "data")

        # register an unknown event
        self.assertRaises(ValueError, s.register, 0, 999999)

        # register an invalid FD
        self.assertRaises(ValueError, s.register, -10, selectors.EVENT_READ)

        # register twice
        self.assertRaises(KeyError, s.register, rd, selectors.EVENT_READ)

        # register the same FD, but with a different object
        self.assertRaises(KeyError, s.register, rd.fileno(),
                          selectors.EVENT_READ) 

def loop(self, process_message: Callable[[bytes], Action]):
        self.sel.register(self.server_socket, selectors.EVENT_READ, data=None)
        try:
            while self.server_status_datasource.running:
                events = self.sel.select(timeout=None)
                for key, mask in events:
                    if key.data is None:
                        self.__accept_wrapper(key.fileobj)
                    else:
                        self.__service_connection(key, mask, process_message)
            self.sel.unregister(self.server_socket)
            self.server_socket.close()
        except KeyboardInterrupt:
            logger.info("caught keyboard interrupt, exiting")
        finally:
            logger.info("server closed")
            self.sel.close() 

def loop(self, loopCondition=lambda: True):
        log.debug("entering multiplexed requestloop")
        while loopCondition():
            try:
                try:
                    events = self.selector.select(config.POLLTIMEOUT)
                except OSError:
                    events = []
                # get all the socket connection objects that have a READ event
                # (the WRITE events are ignored here, they're registered to let timeouts work etc)
                events_per_server = defaultdict(list)
                for key, mask in events:
                    if mask & selectors.EVENT_READ:
                        events_per_server[key.data].append(key.fileobj)
                for server, fileobjs in events_per_server.items():
                    server.events(fileobjs)
                if not events_per_server:
                    self.daemon._housekeeping()
            except socket.timeout:
                pass  # just continue the loop on a timeout
            except KeyboardInterrupt:
                log.debug("stopping on break signal")
                break 

def interact(self):
        """Interaction function, emulates a very dumb telnet client."""
        if sys.platform == "win32":
            self.mt_interact()
            return
        with _TelnetSelector() as selector:
            selector.register(self, selectors.EVENT_READ)
            selector.register(sys.stdin, selectors.EVENT_READ)

            while True:
                for key, events in selector.select():
                    if key.fileobj is self:
                        try:
                            text = self.read_eager()
                        except EOFError:
                            print('*** Connection closed by remote host ***')
                            return
                        if text:
                            sys.stdout.write(text.decode('ascii'))
                            sys.stdout.flush()
                    elif key.fileobj is sys.stdin:
                        line = sys.stdin.readline().encode('ascii')
                        if not line:
                            return
                        self.write(line) 

def test_unregister_after_fd_close_and_reuse(self):
        s = self.SELECTOR()
        self.addCleanup(s.close)
        rd, wr = self.make_socketpair()
        r, w = rd.fileno(), wr.fileno()
        s.register(r, selectors.EVENT_READ)
        s.register(w, selectors.EVENT_WRITE)
        rd2, wr2 = self.make_socketpair()
        rd.close()
        wr.close()
        os.dup2(rd2.fileno(), r)
        os.dup2(wr2.fileno(), w)
        self.addCleanup(os.close, r)
        self.addCleanup(os.close, w)
        s.unregister(r)
        s.unregister(w) 

def test_get_map(self):
        s = self.SELECTOR()
        self.addCleanup(s.close)

        rd, wr = self.make_socketpair()

        keys = s.get_map()
        self.assertFalse(keys)
        self.assertEqual(len(keys), 0)
        self.assertEqual(list(keys), [])
        key = s.register(rd, selectors.EVENT_READ, "data")
        self.assertIn(rd, keys)
        self.assertEqual(key, keys[rd])
        self.assertEqual(len(keys), 1)
        self.assertEqual(list(keys), [rd.fileno()])
        self.assertEqual(list(keys.values()), [key])

        # unknown file obj
        with self.assertRaises(KeyError):
            keys[999999]

        # Read-only mapping
        with self.assertRaises(TypeError):
            del keys[rd] 

def test_select(self):
        s = self.SELECTOR()
        self.addCleanup(s.close)

        rd, wr = self.make_socketpair()

        s.register(rd, selectors.EVENT_READ)
        wr_key = s.register(wr, selectors.EVENT_WRITE)

        result = s.select()
        for key, events in result:
            self.assertTrue(isinstance(key, selectors.SelectorKey))
            self.assertTrue(events)
            self.assertFalse(events & ~(selectors.EVENT_READ |
                                        selectors.EVENT_WRITE))

        self.assertEqual([(wr_key, selectors.EVENT_WRITE)], result) 

def test_select(self):
        s = self.SELECTOR()
        self.addCleanup(s.close)

        rd, wr = self.make_socketpair()

        s.register(rd, selectors.EVENT_READ)
        wr_key = s.register(wr, selectors.EVENT_WRITE)

        result = s.select()
        for key, events in result:
            self.assertTrue(isinstance(key, selectors.SelectorKey))
            self.assertTrue(events)
            self.assertFalse(events & ~(selectors.EVENT_READ |
                                        selectors.EVENT_WRITE))

        self.assertEqual([(wr_key, selectors.EVENT_WRITE)], result) 

def test_timeout(self):
        s = self.SELECTOR()
        self.addCleanup(s.close)

        rd, wr = self.make_socketpair()

        s.register(wr, selectors.EVENT_WRITE)
        t = time()
        self.assertEqual(1, len(s.select(0)))
        self.assertEqual(1, len(s.select(-1)))
        self.assertLess(time() - t, 0.5)

        s.unregister(wr)
        s.register(rd, selectors.EVENT_READ)
        t = time()
        self.assertFalse(s.select(0))
        self.assertFalse(s.select(-1))
        self.assertLess(time() - t, 0.5)

        t0 = time()
        self.assertFalse(s.select(1))
        t1 = time()
        dt = t1 - t0
        # Tolerate 2.0 seconds for very slow buildbots
        self.assertTrue(0.8 <= dt <= 2.0, dt) 

def test_select_interrupt_exc(self):
        s = self.SELECTOR()
        self.addCleanup(s.close)

        rd, wr = self.make_socketpair()

        class InterruptSelect(Exception):
            pass

        def handler(*args):
            raise InterruptSelect

        orig_alrm_handler = signal.signal(signal.SIGALRM, handler)
        self.addCleanup(signal.signal, signal.SIGALRM, orig_alrm_handler)
        self.addCleanup(signal.alarm, 0)

        signal.alarm(1)

        s.register(rd, selectors.EVENT_READ)
        t = time()
        # select() is interrupted by a signal which raises an exception
        with self.assertRaises(InterruptSelect):
            s.select(30)
        # select() was interrupted before the timeout of 30 seconds
        self.assertLess(time() - t, 5.0) 

def test_select_interrupt_noraise(self):
        s = self.SELECTOR()
        self.addCleanup(s.close)

        rd, wr = self.make_socketpair()

        orig_alrm_handler = signal.signal(signal.SIGALRM, lambda *args: None)
        self.addCleanup(signal.signal, signal.SIGALRM, orig_alrm_handler)
        self.addCleanup(signal.alarm, 0)

        signal.alarm(1)

        s.register(rd, selectors.EVENT_READ)
        t = time()
        # select() is interrupted by a signal, but the signal handler doesn't
        # raise an exception, so select() should by retries with a recomputed
        # timeout
        self.assertFalse(s.select(1.5))
        self.assertGreaterEqual(time() - t, 1.0) 

def test_get_map(self):
        s = self.SELECTOR()
        self.addCleanup(s.close)

        rd, wr = self.make_socketpair()

        keys = s.get_map()
        self.assertFalse(keys)
        self.assertEqual(len(keys), 0)
        self.assertEqual(list(keys), [])
        key = s.register(rd, selectors.EVENT_READ, "data")
        self.assertIn(rd, keys)
        self.assertEqual(key, keys[rd])
        self.assertEqual(len(keys), 1)
        self.assertEqual(list(keys), [rd.fileno()])
        self.assertEqual(list(keys.values()), [key])

        # unknown file obj
        with self.assertRaises(KeyError):
            keys[999999]

        # Read-only mapping
        with self.assertRaises(TypeError):
            del keys[rd] 

def __repr__(self):
        info = [self.__class__.__name__]
        if self._pipe is None:
            info.append('closed')
        elif self._closing:
            info.append('closing')
        info.append(f'fd={self._fileno}')
        selector = getattr(self._loop, '_selector', None)
        if self._pipe is not None and selector is not None:
            polling = selector_events._test_selector_event(
                selector, self._fileno, selectors.EVENT_READ)
            if polling:
                info.append('polling')
            else:
                info.append('idle')
        elif self._pipe is not None:
            info.append('open')
        else:
            info.append('closed')
        return '<{}>'.format(' '.join(info)) 

def _remove_reader(self, fd):
        if self.is_closed():
            return False
        try:
            key = self._selector.get_key(fd)
        except KeyError:
            return False
        else:
            mask, (reader, writer) = key.events, key.data
            mask &= ~selectors.EVENT_READ
            if not mask:
                self._selector.unregister(fd)
            else:
                self._selector.modify(fd, mask, (None, writer))

            if reader is not None:
                reader.cancel()
                return True
            else:
                return False 

def test_unregister_after_fd_close_and_reuse(self):
        s = self.SELECTOR()
        self.addCleanup(s.close)
        rd, wr = self.make_socketpair()
        r, w = rd.fileno(), wr.fileno()
        s.register(r, selectors.EVENT_READ)
        s.register(w, selectors.EVENT_WRITE)
        rd2, wr2 = self.make_socketpair()
        rd.close()
        wr.close()
        os.dup2(rd2.fileno(), r)
        os.dup2(wr2.fileno(), w)
        self.addCleanup(os.close, r)
        self.addCleanup(os.close, w)
        s.unregister(r)
        s.unregister(w) 

def test_register(self):
        s = self.SELECTOR()
        self.addCleanup(s.close)

        rd, wr = self.make_socketpair()

        key = s.register(rd, selectors.EVENT_READ, "data")
        self.assertIsInstance(key, selectors.SelectorKey)
        self.assertEqual(key.fileobj, rd)
        self.assertEqual(key.fd, rd.fileno())
        self.assertEqual(key.events, selectors.EVENT_READ)
        self.assertEqual(key.data, "data")

        # register an unknown event
        self.assertRaises(ValueError, s.register, 0, 999999)

        # register an invalid FD
        self.assertRaises(ValueError, s.register, -10, selectors.EVENT_READ)

        # register twice
        self.assertRaises(KeyError, s.register, rd, selectors.EVENT_READ)

        # register the same FD, but with a different object
        self.assertRaises(KeyError, s.register, rd.fileno(),
                          selectors.EVENT_READ) 

def interact(self):
        """Interaction function, emulates a very dumb telnet client."""
        if sys.platform == "win32":
            self.mt_interact()
            return
        with _TelnetSelector() as selector:
            selector.register(self, selectors.EVENT_READ)
            selector.register(sys.stdin, selectors.EVENT_READ)

            while True:
                for key, events in selector.select():
                    if key.fileobj is self:
                        try:
                            text = self.read_eager()
                        except EOFError:
                            print('*** Connection closed by remote host ***')
                            return
                        if text:
                            sys.stdout.write(text.decode('ascii'))
                            sys.stdout.flush()
                    elif key.fileobj is sys.stdin:
                        line = sys.stdin.readline().encode('ascii')
                        if not line:
                            return
                        self.write(line) 

def interact(self):
        """Interaction function, emulates a very dumb telnet client."""
        if sys.platform == "win32":
            self.mt_interact()
            return
        with _TelnetSelector() as selector:
            selector.register(self, selectors.EVENT_READ)
            selector.register(sys.stdin, selectors.EVENT_READ)

            while True:
                for key, events in selector.select():
                    if key.fileobj is self:
                        try:
                            text = self.read_eager()
                        except EOFError:
                            print('*** Connection closed by remote host ***')
                            return
                        if text:
                            sys.stdout.write(text.decode('ascii'))
                            sys.stdout.flush()
                    elif key.fileobj is sys.stdin:
                        line = sys.stdin.readline().encode('ascii')
                        if not line:
                            return
                        self.write(line) 

def serve_forever(self, poll_interval=0.5):
        """Handle one request at a time until shutdown.

        Polls for shutdown every poll_interval seconds. Ignores
        self.timeout. If you need to do periodic tasks, do them in
        another thread.
        """
        self.__is_shut_down.clear()
        try:
            # XXX: Consider using another file descriptor or connecting to the
            # socket to wake this up instead of polling. Polling reduces our
            # responsiveness to a shutdown request and wastes cpu at all other
            # times.
            with _ServerSelector() as selector:
                selector.register(self, selectors.EVENT_READ)

                while not self.__shutdown_request:
                    ready = selector.select(poll_interval)
                    if ready:
                        self._handle_request_noblock()

                    self.service_actions()
        finally:
            self.__shutdown_request = False
            self.__is_shut_down.set() 

def service_connection(key, mask):
    sock = key.fileobj
    data = key.data
    if mask & selectors.EVENT_READ:
        recv_data = sock.recv(BUFFER_SIZE)
        if recv_data:
            data.outb += recv_data
        else:
            print('Closing connection in {}'.format(data.addr))
            selector.unregister(sock)
            sock.close()
    if mask & selectors.EVENT_WRITE:
        if data.outb:
            print('Echo from {} to {}'.format(repr(data.outb), data.addr))
            sent = sock.send(data.outb)
            data.outb = data.outb[sent:] 

def start_connections(host, port, num_conns):
    server_address = (host, port)
    for i in range(0, num_conns):
        connid = i + 1
        print('Starting connection {} towards {}'.format(connid, server_address))
        socket_tcp = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        # We connect using connect_ex () instead of connect ()
        socket_tcp.connect_ex(server_address)
        events = selectors.EVENT_READ | selectors.EVENT_WRITE
        data = types.SimpleNamespace(connid=connid,
                                     msg_total=sum(len(m) for m in messages),
                                     recv_total=0,
                                     messages=list(messages),
                                     outb=b'')
        selector.register(socket_tcp, events, data=data)
    events = selector.select()
    for key, mask in events:
        service_connection(key, mask) 

def test_timeout(self):
        s = self.SELECTOR()
        self.addCleanup(s.close)

        rd, wr = self.make_socketpair()

        s.register(wr, selectors.EVENT_WRITE)
        t = time()
        self.assertEqual(1, len(s.select(0)))
        self.assertEqual(1, len(s.select(-1)))
        self.assertLess(time() - t, 0.5)

        s.unregister(wr)
        s.register(rd, selectors.EVENT_READ)
        t = time()
        self.assertFalse(s.select(0))
        self.assertFalse(s.select(-1))
        self.assertLess(time() - t, 0.5)

        t0 = time()
        self.assertFalse(s.select(1))
        t1 = time()
        dt = t1 - t0
        # Tolerate 2.0 seconds for very slow buildbots
        self.assertTrue(0.8 <= dt <= 2.0, dt) 

def write(self, message: StateDTO):
        events = self.sel.select(timeout=5)
        key = events[0][0]
        client_socket = key.fileobj
        data = key.data
        self.sel.modify(client_socket, selectors.EVENT_WRITE, data)
        logger.info(f'echoing ${data}')
        data.outb = str(message.json())
        sent = client_socket.send(data.outb.encode('utf-8'))
        data.outb = data.outb[sent:]
        self.sel.modify(client_socket, selectors.EVENT_READ, data) 

def __service_connection(self, key, mask, process_message):
        fileobj = key.fileobj
        data = key.data
        if mask & selectors.EVENT_READ:
            data = self.__read(data, fileobj, process_message)
        if mask & selectors.EVENT_WRITE:
            self.__write(data, fileobj) 

def start_connections(self, host, port):

        server_address = (host, port)

        client_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        client_socket.setblocking(False)
        client_socket.connect_ex(server_address)
        events = selectors.EVENT_READ | selectors.EVENT_WRITE
        data = types.SimpleNamespace(
            connid=self.uuid,
            outb=b'',
        )
        self.sel.register(client_socket, events, data=data)