Python multiprocessing.pool.join() Examples

def _normalize_pool_parameter(self, pool_param, param_name):
        if isinstance(pool_param, (mp.pool.Pool, mp.pool.ThreadPool)):
            return pool_param
        if pool_param is None:
            return None
        if not (hasattr(pool_param, '__hash__') and hasattr(pool_param, '__eq__')): # pragma: no cover
            types = [
                'multiprocessing.pool.Pool',
                'multiprocessing.pool.ThreadPool',
                'None', 'hashable',
            ]
            raise TypeError('`{}` parameter should be one of {}'.format(
                param_name, ', '.join(types)
            ))
        with self._lock:
            if pool_param not in self._aliases:
                p = mp.pool.ThreadPool(mp.cpu_count())
                self._aliases[pool_param] = p
                self._aliases_per_pool[p] = [pool_param]
                self._managed_pools.add(p)
        return self._aliases[pool_param] 

def test_poll_eintr(self):
        got_signal = [False]
        def record(*args):
            got_signal[0] = True
        pid = os.getpid()
        oldhandler = signal.signal(signal.SIGUSR1, record)
        try:
            killer = self.Process(target=self._killer, args=(pid,))
            killer.start()
            try:
                p = self.Process(target=time.sleep, args=(2,))
                p.start()
                p.join()
            finally:
                killer.join()
            self.assertTrue(got_signal[0])
            self.assertEqual(p.exitcode, 0)
        finally:
            signal.signal(signal.SIGUSR1, oldhandler)

#
# Test to verify handle verification, see issue 3321
# 

def test_sharedctypes(self, lock=False):
        x = Value('i', 7, lock=lock)
        y = Value(c_double, 1.0/3.0, lock=lock)
        foo = Value(_Foo, 3, 2, lock=lock)
        arr = self.Array('d', list(range(10)), lock=lock)
        string = self.Array('c', 20, lock=lock)
        string.value = latin('hello')

        p = self.Process(target=self._double, args=(x, y, foo, arr, string))
        p.daemon = True
        p.start()
        p.join()

        self.assertEqual(x.value, 14)
        self.assertAlmostEqual(y.value, 2.0/3.0)
        self.assertEqual(foo.x, 6)
        self.assertAlmostEqual(foo.y, 4.0)
        for i in range(10):
            self.assertAlmostEqual(arr[i], i*2)
        self.assertEqual(string.value, latin('hellohello')) 

def test_dont_merge(self):
        a, b = self.Pipe()
        self.assertEqual(a.poll(0.0), False)
        self.assertEqual(a.poll(0.1), False)

        p = self.Process(target=self._child_dont_merge, args=(b,))
        p.start()

        self.assertEqual(a.recv_bytes(), b'a')
        self.assertEqual(a.poll(1.0), True)
        self.assertEqual(a.poll(1.0), True)
        self.assertEqual(a.recv_bytes(), b'b')
        self.assertEqual(a.poll(1.0), True)
        self.assertEqual(a.poll(1.0), True)
        self.assertEqual(a.poll(0.0), True)
        self.assertEqual(a.recv_bytes(), b'cd')

        p.join()

#
# Test of sending connection and socket objects between processes
# 

def test_sentinel(self):
        if self.TYPE == "threads":
            self.skipTest('test not appropriate for {}'.format(self.TYPE))
        event = self.Event()
        p = self.Process(target=self._test_sentinel, args=(event,))
        with self.assertRaises(ValueError):
            p.sentinel
        p.start()
        self.addCleanup(p.join)
        sentinel = p.sentinel
        self.assertIsInstance(sentinel, int)
        self.assertFalse(wait_for_handle(sentinel, timeout=0.0))
        event.set()
        p.join()
        self.assertTrue(wait_for_handle(sentinel, timeout=1))

#
#
# 

def test_stderr_flush(self):
        # sys.stderr is flushed at process shutdown (issue #13812)
        if self.TYPE == "threads":
            self.skipTest('test not appropriate for {}'.format(self.TYPE))

        testfn = test.support.TESTFN
        self.addCleanup(test.support.unlink, testfn)
        proc = self.Process(target=self._test_stderr_flush, args=(testfn,))
        proc.start()
        proc.join()
        with open(testfn, 'r') as f:
            err = f.read()
            # The whole traceback was printed
            self.assertIn("ZeroDivisionError", err)
            self.assertIn("test_multiprocessing.py", err)
            self.assertIn("1/0 # MARKER", err) 

def test_large_fd_transfer(self):
        # With fd > 256 (issue #11657)
        if self.TYPE != 'processes':
            self.skipTest("only makes sense with processes")
        conn, child_conn = self.Pipe(duplex=True)

        p = self.Process(target=self._writefd, args=(child_conn, b"bar", True))
        p.daemon = True
        p.start()
        self.addCleanup(test.support.unlink, test.support.TESTFN)
        with open(test.support.TESTFN, "wb") as f:
            fd = f.fileno()
            for newfd in range(256, MAXFD):
                if not self._is_fd_assigned(newfd):
                    break
            else:
                self.fail("could not find an unassigned large file descriptor")
            os.dup2(fd, newfd)
            try:
                reduction.send_handle(conn, newfd, p.pid)
            finally:
                os.close(newfd)
        p.join()
        with open(test.support.TESTFN, "rb") as f:
            self.assertEqual(f.read(), b"bar") 

def test_fd_transfer(self):
        if self.TYPE != 'processes':
            self.skipTest("only makes sense with processes")
        conn, child_conn = self.Pipe(duplex=True)

        p = self.Process(target=self._writefd, args=(child_conn, b"foo"))
        p.daemon = True
        p.start()
        self.addCleanup(test.support.unlink, test.support.TESTFN)
        with open(test.support.TESTFN, "wb") as f:
            fd = f.fileno()
            if msvcrt:
                fd = msvcrt.get_osfhandle(fd)
            reduction.send_handle(conn, fd, p.pid)
        p.join()
        with open(test.support.TESTFN, "rb") as f:
            self.assertEqual(f.read(), b"foo") 

def test_spawn_close(self):
        # We test that a pipe connection can be closed by parent
        # process immediately after child is spawned.  On Windows this
        # would have sometimes failed on old versions because
        # child_conn would be closed before the child got a chance to
        # duplicate it.
        conn, child_conn = self.Pipe()

        p = self.Process(target=self._echo, args=(child_conn,))
        p.daemon = True
        p.start()
        child_conn.close()    # this might complete before child initializes

        msg = latin('hello')
        conn.send_bytes(msg)
        self.assertEqual(conn.recv_bytes(), msg)

        conn.send_bytes(SENTINEL)
        conn.close()
        p.join() 

def test_ignore(self):
        conn, child_conn = multiprocessing.Pipe()
        try:
            p = multiprocessing.Process(target=self._test_ignore,
                                        args=(child_conn,))
            p.daemon = True
            p.start()
            child_conn.close()
            self.assertEqual(conn.recv(), 'ready')
            time.sleep(0.1)
            os.kill(p.pid, signal.SIGUSR1)
            time.sleep(0.1)
            conn.send(1234)
            self.assertEqual(conn.recv(), 1234)
            time.sleep(0.1)
            os.kill(p.pid, signal.SIGUSR1)
            self.assertEqual(conn.recv_bytes(), b'x'*(1024*1024))
            time.sleep(0.1)
            p.join()
        finally:
            conn.close() 

def test_pool_worker_lifetime_early_close(self):
        # Issue #10332: closing a pool whose workers have limited lifetimes
        # before all the tasks completed would make join() hang.
        p = multiprocessing.Pool(3, maxtasksperchild=1)
        results = []
        for i in range(6):
            results.append(p.apply_async(sqr, (i, 0.3)))
        p.close()
        p.join()
        # check the results
        for (j, res) in enumerate(results):
            self.assertEqual(res.get(), sqr(j))

#
# Test of creating a customized manager class
# 

def test_value(self, raw=False):
        if raw:
            values = [self.RawValue(code, value)
                      for code, value, _ in self.codes_values]
        else:
            values = [self.Value(code, value)
                      for code, value, _ in self.codes_values]

        for sv, cv in zip(values, self.codes_values):
            self.assertEqual(sv.value, cv[1])

        proc = self.Process(target=self._test, args=(values,))
        proc.daemon = True
        proc.start()
        proc.join()

        for sv, cv in zip(values, self.codes_values):
            self.assertEqual(sv.value, cv[2]) 

def test_active_children(self):
        self.assertEqual(type(self.active_children()), list)

        p = self.Process(target=time.sleep, args=(DELTA,))
        self.assertNotIn(p, self.active_children())

        p.daemon = True
        p.start()
        self.assertIn(p, self.active_children())

        p.join()
        self.assertNotIn(p, self.active_children()) 

def _close(self):
        for pool in self._managed_pools:
            pool.terminate()
        for pool in self._managed_pools:
            pool.join()
        self._aliases.clear()
        self._aliases_per_pool.clear()
        self._managed_pools.clear() 

def test_process(self):
        q = self.Queue(1)
        e = self.Event()
        args = (q, 1, 2)
        kwargs = {'hello':23, 'bye':2.54}
        name = 'SomeProcess'
        p = self.Process(
            target=self._test, args=args, kwargs=kwargs, name=name
            )
        p.daemon = True
        current = self.current_process()

        if self.TYPE != 'threads':
            self.assertEqual(p.authkey, current.authkey)
        self.assertEqual(p.is_alive(), False)
        self.assertEqual(p.daemon, True)
        self.assertNotIn(p, self.active_children())
        self.assertTrue(type(self.active_children()) is list)
        self.assertEqual(p.exitcode, None)

        p.start()

        self.assertEqual(p.exitcode, None)
        self.assertEqual(p.is_alive(), True)
        self.assertIn(p, self.active_children())

        self.assertEqual(q.get(), args[1:])
        self.assertEqual(q.get(), kwargs)
        self.assertEqual(q.get(), p.name)
        if self.TYPE != 'threads':
            self.assertEqual(q.get(), current.authkey)
            self.assertEqual(q.get(), p.pid)

        p.join()

        self.assertEqual(p.exitcode, 0)
        self.assertEqual(p.is_alive(), False)
        self.assertNotIn(p, self.active_children()) 

def test_closefd(self):
        if not HAS_REDUCTION:
            raise unittest.SkipTest('requires fd pickling')

        reader, writer = multiprocessing.Pipe()
        fd = self.get_high_socket_fd()
        try:
            p = multiprocessing.Process(target=self._test_closefds,
                                        args=(writer, fd))
            p.start()
            writer.close()
            e = reader.recv()
            p.join(timeout=5)
        finally:
            self.close(fd)
            writer.close()
            reader.close()

        if multiprocessing.get_start_method() == 'fork':
            self.assertIs(e, None)
        else:
            WSAENOTSOCK = 10038
            self.assertIsInstance(e, OSError)
            self.assertTrue(e.errno == errno.EBADF or
                            e.winerror == WSAENOTSOCK, e)

#
# Issue #17097: EINTR should be ignored by recv(), send(), accept() etc
# 

def test_lock(self):
        r, w = multiprocessing.Pipe(False)
        l = util.ForkAwareThreadLock()
        old_size = len(util._afterfork_registry)
        p = multiprocessing.Process(target=self.child, args=(5, w))
        p.start()
        w.close()
        new_size = r.recv()
        p.join(timeout=5)
        self.assertLessEqual(new_size, old_size)

#
# Check that non-forked child processes do not inherit unneeded fds/handles
# 

def child(cls, n, conn):
        if n > 1:
            p = multiprocessing.Process(target=cls.child, args=(n-1, conn))
            p.start()
            conn.close()
            p.join(timeout=5)
        else:
            conn.send(len(util._afterfork_registry))
        conn.close() 

def test_noforkbomb(self):
        sm = multiprocessing.get_start_method()
        name = os.path.join(os.path.dirname(__file__), 'mp_fork_bomb.py')
        if sm != 'fork':
            rc, out, err = test.support.script_helper.assert_python_failure(name, sm)
            self.assertEqual(out, b'')
            self.assertIn(b'RuntimeError', err)
        else:
            rc, out, err = test.support.script_helper.assert_python_ok(name, sm)
            self.assertEqual(out.rstrip(), b'123')
            self.assertEqual(err, b'')

#
# Issue #17555: ForkAwareThreadLock
# 

def check_context(self, ctx):
        r, w = ctx.Pipe(duplex=False)
        p = ctx.Process(target=self._check_context, args=(w,))
        p.start()
        w.close()
        child_method = r.recv()
        r.close()
        p.join()
        self.assertEqual(child_method, ctx.get_start_method()) 

def test_terminate(self):
        result = self.pool.map_async(
            time.sleep, [0.1 for i in range(10000)], chunksize=1
            )
        self.pool.terminate()
        join = TimingWrapper(self.pool.join)
        join()
        self.assertLess(join.elapsed, 0.5) 

def test_finalize(self):
        conn, child_conn = self.Pipe()

        p = self.Process(target=self._test_finalize, args=(child_conn,))
        p.daemon = True
        p.start()
        p.join()

        result = [obj for obj in iter(conn.recv, 'STOP')]
        self.assertEqual(result, ['a', 'b', 'd10', 'd03', 'd02', 'd01', 'e'])

#
# Test that from ... import * works for each module
# 

def _test_recursion(cls, wconn, id):
        wconn.send(id)
        if len(id) < 2:
            for i in range(2):
                p = cls.Process(
                    target=cls._test_recursion, args=(wconn, id+[i])
                    )
                p.start()
                p.join() 

def test_empty_iterable(self):
        # See Issue 12157
        p = self.Pool(1)

        self.assertEqual(p.map(sqr, []), [])
        self.assertEqual(list(p.imap(sqr, [])), [])
        self.assertEqual(list(p.imap_unordered(sqr, [])), [])
        self.assertEqual(p.map_async(sqr, []).get(), [])

        p.close()
        p.join() 

def test_boundaries(self):
        r, w = self.Pipe(False)
        p = self.Process(target=self._child_boundaries, args=(r,))
        p.start()
        time.sleep(2)
        L = [b"first", b"second"]
        for obj in L:
            w.send_bytes(obj)
        w.close()
        p.join()
        self.assertIn(r.recv_bytes(), L) 

def test_strings(self):
        strings = (b'hello', b'', b'a', b'b', b'', b'bye', b'', b'lop')
        a, b = self.Pipe()
        p = self.Process(target=self._child_strings, args=(b, strings))
        p.start()

        for s in strings:
            for i in range(200):
                if a.poll(0.01):
                    break
            x = a.recv_bytes()
            self.assertEqual(s, x)

        p.join() 

def test_async_error_callback(self):
        p = multiprocessing.Pool(2)

        scratchpad = [None]
        def errback(exc):
            scratchpad[0] = exc

        res = p.apply_async(raising, error_callback=errback)
        self.assertRaises(KeyError, res.get)
        self.assertTrue(scratchpad[0])
        self.assertIsInstance(scratchpad[0], KeyError)

        p.close()
        p.join() 

def test_issue14725(self):
        l = self.connection.Listener()
        p = self.Process(target=self._test, args=(l.address,))
        p.daemon = True
        p.start()
        time.sleep(1)
        # On Windows the client process should by now have connected,
        # written data and closed the pipe handle by now.  This causes
        # ConnectNamdedPipe() to fail with ERROR_NO_DATA.  See Issue
        # 14725.
        conn = l.accept()
        self.assertEqual(conn.recv(), 'hello')
        conn.close()
        p.join()
        l.close() 

def test_listener_client(self):
        for family in self.connection.families:
            l = self.connection.Listener(family=family)
            p = self.Process(target=self._test, args=(l.address,))
            p.daemon = True
            p.start()
            conn = l.accept()
            self.assertEqual(conn.recv(), 'hello')
            p.join()
            l.close() 

def test_pool_worker_lifetime(self):
        p = multiprocessing.Pool(3, maxtasksperchild=10)
        self.assertEqual(3, len(p._pool))
        origworkerpids = [w.pid for w in p._pool]
        # Run many tasks so each worker gets replaced (hopefully)
        results = []
        for i in range(100):
            results.append(p.apply_async(sqr, (i, )))
        # Fetch the results and verify we got the right answers,
        # also ensuring all the tasks have completed.
        for (j, res) in enumerate(results):
            self.assertEqual(res.get(), sqr(j))
        # Refill the pool
        p._repopulate_pool()
        # Wait until all workers are alive
        # (countdown * DELTA = 5 seconds max startup process time)
        countdown = 50
        while countdown and not all(w.is_alive() for w in p._pool):
            countdown -= 1
            time.sleep(DELTA)
        finalworkerpids = [w.pid for w in p._pool]
        # All pids should be assigned.  See issue #7805.
        self.assertNotIn(None, origworkerpids)
        self.assertNotIn(None, finalworkerpids)
        # Finally, check that the worker pids have changed
        self.assertNotEqual(sorted(origworkerpids), sorted(finalworkerpids))
        p.close()
        p.join()