class ExtractStream(object):
"""Used to receive messages outside of an operator.
Args:
read_stream (ReadStream): the stream from which to read messages.
"""
def __init__(self, read_stream):
self._py_extract_stream = PyExtractStream(read_stream._py_read_stream)
def is_closed(self):
"""Whether the stream is closed.
Returns True if the a top watermark message was sent or the
ExtractStream was unable to successfully set up.
"""
return self._py_extract_stream.is_closed()
def read(self):
"""Blocks until a message is read from the stream."""
return _parse_message(self._py_extract_stream.read())
def try_read(self):
"""Tries to read a mesage from the stream.
Returns None if no messages are available at the moment.
"""
internal_msg = self._py_extract_stream.try_read()
if internal_msg is None:
return None
return _parse_message(internal_msg)
def __init__(self,
read_stream: ReadStream,
_name: Union[str, None] = None):
if not isinstance(read_stream, ReadStream):
raise ValueError(
"ExtractStream needs to be initialized with a ReadStream. "
"Received a {}".format(type(read_stream)))
self._py_extract_stream = PyExtractStream(
read_stream._py_read_stream,
_name,
)
class ExtractStream:
"""An :py:class:`ExtractStream` enables drivers to read data from a
running ERDOS applications.
The driver can initialize a new :py:class:`ExtractStream` by passing the
instance of :py:class:`OperatorStream` returned by the :code:`connect`
family of functions. Similar to a :py:class:`ReadStream`, an
:py:class:`ExtractStream` provides :py:meth:`.read` and
:py:meth:`.try_read` for reading data published on the corresponding
:py:class:`OperatorStream`.
Args:
stream: The stream from which to read messages.
"""
def __init__(self, stream: OperatorStream):
if not isinstance(stream, OperatorStream):
raise ValueError(
"ExtractStream needs to be initialized with a Stream. "
"Received a {}".format(type(stream)))
self._py_extract_stream = PyExtractStream(stream._internal_stream)
@property
def name(self) -> str:
"""The name of the stream. The stream ID if no name was given."""
return self._py_extract_stream.name()
@property
def id(self) -> str:
"""The id of the ExtractStream."""
return uuid.UUID(self._py_extract_stream.id())
def is_closed(self) -> bool:
"""Whether the stream is closed.
Returns True if the a top watermark message was sent or the
:py:class:`ExtractStream` was unable to successfully set up.
"""
return self._py_extract_stream.is_closed()
def read(self) -> Message:
"""Blocks until a message is read from the stream."""
return _parse_message(self._py_extract_stream.read())
def try_read(self) -> Union[Message, None]:
"""Tries to read a mesage from the stream.
Returns :code:`None` if no messages are available at the moment.
"""
internal_msg = self._py_extract_stream.try_read()
if internal_msg is None:
return None
return _parse_message(internal_msg)
def __init__(self, stream: OperatorStream[T]) -> None:
if not isinstance(stream, OperatorStream) or not isinstance(
stream._internal_stream, PyOperatorStream):
raise ValueError(
"ExtractStream needs to be initialized with a Stream. "
"Received a {}".format(type(stream)))
self._py_extract_stream: PyExtractStream = PyExtractStream(
stream._internal_stream)
class ExtractStream(object):
"""Used to receive messages outside of an operator.
Args:
read_stream (ReadStream): the stream from which to read messages.
"""
def __init__(self, read_stream):
self._py_extract_stream = PyExtractStream(read_stream._py_read_stream)
def read(self):
"""Blocks until a message is read from the stream."""
return _parse_message(self._py_extract_stream.read())
def try_read(self):
"""Tries to read a mesage from the stream.
Returns None if no messages are available at the moment.
"""
internal_msg = self._py_extract_stream.try_read()
if internal_msg is None:
return None
return _parse_message(internal_msg)
def __init__(self, read_stream):
self._py_extract_stream = PyExtractStream(read_stream._py_read_stream)