def run_consumer(name, delay):
buffer = RingBuffer(name=name, size=0, create=False)
shutdown = False
def terminate(signum, frame):
nonlocal shutdown
print(
"Received=",
signal.Signals(signum).name,
"Attempting graceful shutdown of consumer",
)
shutdown = True
signal.signal(signal.SIGTERM, terminate)
signal.signal(signal.SIGINT, terminate)
try:
while not shutdown:
b = buffer.get()
print(f"Message: {decode_message(b)}Reader: {buffer.reader_pos()} Writer: {buffer.writer_pos()}")
time.sleep(delay)
buffer.close()
print(f"Destroyed shared memory buffer {name}")
except Exception as ex:
buffer.close()
print(f"Error {str(ex)}. Destroying shared memory buffer and exiting")
traceback.print_exc(file=sys.stdout)
sys.exit(1)
class RingBufferTests(unittest.TestCase):
def setUp(self):
self.capacity = 5
self.buffer = RingBuffer(self.capacity)
def test_new_buffer_has_appropriate_capacity(self):
self.assertEqual(self.buffer.capacity, self.capacity)
def test_adding_one_element_to_buffer(self):
self.buffer.append('a')
self.assertEqual(self.buffer.get(), ['a'])
def test_filling_buffer_to_capacity(self):
self.buffer.append('a')
self.buffer.append('b')
self.buffer.append('c')
self.buffer.append('d')
self.buffer.append('e')
self.assertEqual(self.buffer.get(), ['a', 'b', 'c', 'd', 'e'])
def test_adding_one_element_to_full_buffer(self):
self.buffer.append('a')
self.buffer.append('b')
self.buffer.append('c')
self.buffer.append('d')
self.buffer.append('e')
self.buffer.append('f')
self.assertEqual(self.buffer.get(), ['f', 'b', 'c', 'd', 'e'])
def test_adding_many_elements_to_full_buffer(self):
self.buffer.append('a')
self.buffer.append('b')
self.buffer.append('c')
self.buffer.append('d')
self.buffer.append('e')
self.buffer.append('f')
self.buffer.append('g')
self.buffer.append('h')
self.buffer.append('i')
self.assertEqual(self.buffer.get(), ['f', 'g', 'h', 'i', 'e'])
def test_adding_50_elements_to_buffer(self):
for i in range(50):
self.buffer.append(i)
self.assertEqual(self.buffer.get(), [45, 46, 47, 48, 49])
def test_reader_reads_data_and_moves_offset_when_writer_wraps_around(buffer):
read_buff = RingBuffer(name=buffer.name, size=0, create=False)
messages = _messages(8)
for m in messages[:6]:
buffer.put(m)
[read_buff.get() for _ in range(6)]
for m in messages[6:]:
buffer.put(m)
got = [_decode_message(read_buff.get()) for _ in range(2)]
expected = [_decode_message(m) for m in messages[6:]]
assert got == expected
assert read_buff.reader_pos() == 32
def test_reader_does_not_go_past_writer_when_writer_wraps_around(buffer):
read_buff = RingBuffer(name=buffer.name, size=0, create=False)
messages = _messages(8)
for m in messages[:6]:
buffer.put(m)
[read_buff.get() for _ in range(6)]
for m in messages[6:7]:
buffer.put(m)
with pytest.raises(WriterCollisionError) as excinfo:
[read_buff.get() for _ in range(2)]
assert str(
excinfo.value
) == "Writer cursor at 16. Reader cursor attemping to read [16 :32]"
def test_reader_reads_data_and_moves_offset(buffer):
read_buff = RingBuffer(name=buffer.name, size=0, create=False)
messages = _messages(3)
expected = [_decode_message(m) for m in messages]
for m in messages:
buffer.put(m)
got = [_decode_message(read_buff.get()) for _ in range(3)]
assert got == expected
assert read_buff.reader_pos() == 48
def test_reader_does_not_go_past_writer(buffer):
read_buff = RingBuffer(name=buffer.name, size=0, create=False)
messages = _messages(3)
for m in messages:
buffer.put(m)
with pytest.raises(WriterCollisionError) as excinfo:
[read_buff.get() for _ in range(5)]
assert str(
excinfo.value
) == "Writer cursor at 48. Reader cursor attemping to read [48 :64]"