def wait(
self,
timeout: Optional[Union[float, datetime.timedelta]] = None
) -> Awaitable[None]:
"""Block until the internal flag is true.
Returns an awaitable, which raises `tornado.util.TimeoutError` after a
timeout.
"""
fut = Future() # type: Future[None]
if self._value:
fut.set_result(None)
return fut
self._waiters.add(fut)
fut.add_done_callback(lambda fut: self._waiters.remove(fut))
if timeout is None:
return fut
else:
timeout_fut = gen.with_timeout(timeout, fut)
# This is a slightly clumsy workaround for the fact that
# gen.with_timeout doesn't cancel its futures. Cancelling
# fut will remove it from the waiters list.
timeout_fut.add_done_callback(lambda tf: fut.cancel()
if not fut.done() else None)
return timeout_fut
class HTTP1Connection(httputil.HTTPConnection):
"""Implements the HTTP/1.x protocol.
This class can be on its own for clients, or via `HTTP1ServerConnection`
for servers.
"""
def __init__(
self,
stream: iostream.IOStream,
is_client: bool,
params: Optional[HTTP1ConnectionParameters] = None,
context: Optional[object] = None,
) -> None:
"""
:arg stream: an `.IOStream`
:arg bool is_client: client or server
:arg params: a `.HTTP1ConnectionParameters` instance or ``None``
:arg context: an opaque application-defined object that can be accessed
as ``connection.context``.
"""
self.is_client = is_client
self.stream = stream
if params is None:
params = HTTP1ConnectionParameters()
self.params = params
self.context = context
self.no_keep_alive = params.no_keep_alive
# The body limits can be altered by the delegate, so save them
# here instead of just referencing self.params later.
self._max_body_size = self.params.max_body_size or self.stream.max_buffer_size
self._body_timeout = self.params.body_timeout
# _write_finished is set to True when finish() has been called,
# i.e. there will be no more data sent. Data may still be in the
# stream's write buffer.
self._write_finished = False
# True when we have read the entire incoming body.
self._read_finished = False
# _finish_future resolves when all data has been written and flushed
# to the IOStream.
self._finish_future = Future() # type: Future[None]
# If true, the connection should be closed after this request
# (after the response has been written in the server side,
# and after it has been read in the client)
self._disconnect_on_finish = False
self._clear_callbacks()
# Save the start lines after we read or write them; they
# affect later processing (e.g. 304 responses and HEAD methods
# have content-length but no bodies)
self._request_start_line = None # type: Optional[httputil.RequestStartLine]
self._response_start_line = None # type: Optional[httputil.ResponseStartLine]
self._request_headers = None # type: Optional[httputil.HTTPHeaders]
# True if we are writing output with chunked encoding.
self._chunking_output = False
# While reading a body with a content-length, this is the
# amount left to read.
self._expected_content_remaining = None # type: Optional[int]
# A Future for our outgoing writes, returned by IOStream.write.
self._pending_write = None # type: Optional[Future[None]]
def read_response(
self, delegate: httputil.HTTPMessageDelegate) -> Awaitable[bool]:
"""Read a single HTTP response.
Typical client-mode usage is to write a request using `write_headers`,
`write`, and `finish`, and then call ``read_response``.
:arg delegate: a `.HTTPMessageDelegate`
Returns a `.Future` that resolves to a bool after the full response has
been read. The result is true if the stream is still open.
"""
if self.params.decompress:
delegate = _GzipMessageDelegate(delegate, self.params.chunk_size)
return self._read_message(delegate)
async def _read_message(self,
delegate: httputil.HTTPMessageDelegate) -> bool:
need_delegate_close = False
try:
header_future = self.stream.read_until_regex(
b"\r?\n\r?\n", max_bytes=self.params.max_header_size)
if self.params.header_timeout is None:
header_data = await header_future
else:
try:
header_data = await gen.with_timeout(
self.stream.io_loop.time() +
self.params.header_timeout,
header_future,
quiet_exceptions=iostream.StreamClosedError,
)
except gen.TimeoutError:
self.close()
return False
start_line_str, headers = self._parse_headers(header_data)
if self.is_client:
resp_start_line = httputil.parse_response_start_line(
start_line_str)
self._response_start_line = resp_start_line
start_line = (
resp_start_line
) # type: Union[httputil.RequestStartLine, httputil.ResponseStartLine]
# TODO: this will need to change to support client-side keepalive
self._disconnect_on_finish = False
else:
req_start_line = httputil.parse_request_start_line(
start_line_str)
self._request_start_line = req_start_line
self._request_headers = headers
start_line = req_start_line
self._disconnect_on_finish = not self._can_keep_alive(
req_start_line, headers)
need_delegate_close = True
with _ExceptionLoggingContext(app_log):
header_recv_future = delegate.headers_received(
start_line, headers)
if header_recv_future is not None:
await header_recv_future
if self.stream is None:
# We've been detached.
need_delegate_close = False
return False
skip_body = False
if self.is_client:
assert isinstance(start_line, httputil.ResponseStartLine)
if (self._request_start_line is not None
and self._request_start_line.method == "HEAD"):
skip_body = True
code = start_line.code
if code == 304:
# 304 responses may include the content-length header
# but do not actually have a body.
# http://tools.ietf.org/html/rfc7230#section-3.3
skip_body = True
if code >= 100 and code < 200:
# 1xx responses should never indicate the presence of
# a body.
if "Content-Length" in headers or "Transfer-Encoding" in headers:
raise httputil.HTTPInputError(
"Response code %d cannot have body" % code)
# TODO: client delegates will get headers_received twice
# in the case of a 100-continue. Document or change?
await self._read_message(delegate)
else:
if headers.get(
"Expect"
) == "100-continue" and not self._write_finished:
self.stream.write(b"HTTP/1.1 100 (Continue)\r\n\r\n")
if not skip_body:
body_future = self._read_body(
resp_start_line.code if self.is_client else 0, headers,
delegate)
if body_future is not None:
if self._body_timeout is None:
await body_future
else:
try:
await gen.with_timeout(
self.stream.io_loop.time() +
self._body_timeout,
body_future,
quiet_exceptions=iostream.StreamClosedError,
)
except gen.TimeoutError:
gen_log.info("Timeout reading body from %s",
self.context)
self.stream.close()
return False
self._read_finished = True
if not self._write_finished or self.is_client:
need_delegate_close = False
with _ExceptionLoggingContext(app_log):
delegate.finish()
# If we're waiting for the application to produce an asynchronous
# response, and we're not detached, register a close callback
# on the stream (we didn't need one while we were reading)
if (not self._finish_future.done() and self.stream is not None
and not self.stream.closed()):
self.stream.set_close_callback(self._on_connection_close)
await self._finish_future
if self.is_client and self._disconnect_on_finish:
self.close()
if self.stream is None:
return False
except httputil.HTTPInputError as e:
gen_log.info("Malformed HTTP message from %s: %s", self.context, e)
if not self.is_client:
await self.stream.write(b"HTTP/1.1 400 Bad Request\r\n\r\n")
self.close()
return False
finally:
if need_delegate_close:
with _ExceptionLoggingContext(app_log):
delegate.on_connection_close()
header_future = None # type: ignore
self._clear_callbacks()
return True
def _clear_callbacks(self) -> None:
"""Clears the callback attributes.
This allows the request handler to be garbage collected more
quickly in CPython by breaking up reference cycles.
"""
self._write_callback = None
self._write_future = None # type: Optional[Future[None]]
self._close_callback = None # type: Optional[Callable[[], None]]
if self.stream is not None:
self.stream.set_close_callback(None)
def set_close_callback(self, callback: Optional[Callable[[],
None]]) -> None:
"""Sets a callback that will be run when the connection is closed.
Note that this callback is slightly different from
`.HTTPMessageDelegate.on_connection_close`: The
`.HTTPMessageDelegate` method is called when the connection is
closed while receiving a message. This callback is used when
there is not an active delegate (for example, on the server
side this callback is used if the client closes the connection
after sending its request but before receiving all the
response.
"""
self._close_callback = callback
def _on_connection_close(self) -> None:
# Note that this callback is only registered on the IOStream
# when we have finished reading the request and are waiting for
# the application to produce its response.
if self._close_callback is not None:
callback = self._close_callback
self._close_callback = None
callback()
if not self._finish_future.done():
future_set_result_unless_cancelled(self._finish_future, None)
self._clear_callbacks()
def close(self) -> None:
if self.stream is not None:
self.stream.close()
self._clear_callbacks()
if not self._finish_future.done():
future_set_result_unless_cancelled(self._finish_future, None)
def detach(self) -> iostream.IOStream:
"""Take control of the underlying stream.
Returns the underlying `.IOStream` object and stops all further
HTTP processing. May only be called during
`.HTTPMessageDelegate.headers_received`. Intended for implementing
protocols like websockets that tunnel over an HTTP handshake.
"""
self._clear_callbacks()
stream = self.stream
self.stream = None # type: ignore
if not self._finish_future.done():
future_set_result_unless_cancelled(self._finish_future, None)
return stream
def set_body_timeout(self, timeout: float) -> None:
"""Sets the body timeout for a single request.
Overrides the value from `.HTTP1ConnectionParameters`.
"""
self._body_timeout = timeout
def set_max_body_size(self, max_body_size: int) -> None:
"""Sets the body size limit for a single request.
Overrides the value from `.HTTP1ConnectionParameters`.
"""
self._max_body_size = max_body_size
def write_headers(
self,
start_line: Union[httputil.RequestStartLine,
httputil.ResponseStartLine],
headers: httputil.HTTPHeaders,
chunk: Optional[bytes] = None,
) -> "Future[None]":
"""Implements `.HTTPConnection.write_headers`."""
lines = []
if self.is_client:
assert isinstance(start_line, httputil.RequestStartLine)
self._request_start_line = start_line
lines.append(
utf8("%s %s HTTP/1.1" % (start_line[0], start_line[1])))
# Client requests with a non-empty body must have either a
# Content-Length or a Transfer-Encoding.
self._chunking_output = (
start_line.method in ("POST", "PUT", "PATCH")
and "Content-Length" not in headers
and ("Transfer-Encoding" not in headers
or headers["Transfer-Encoding"] == "chunked"))
else:
assert isinstance(start_line, httputil.ResponseStartLine)
assert self._request_start_line is not None
assert self._request_headers is not None
self._response_start_line = start_line
lines.append(
utf8("HTTP/1.1 %d %s" % (start_line[1], start_line[2])))
self._chunking_output = (
# TODO: should this use
# self._request_start_line.version or
# start_line.version?
self._request_start_line.version == "HTTP/1.1"
# 1xx, 204 and 304 responses have no body (not even a zero-length
# body), and so should not have either Content-Length or
# Transfer-Encoding headers.
and start_line.code not in (204, 304) and
(start_line.code < 100 or start_line.code >= 200)
# No need to chunk the output if a Content-Length is specified.
and "Content-Length" not in headers
# Applications are discouraged from touching Transfer-Encoding,
# but if they do, leave it alone.
and "Transfer-Encoding" not in headers)
# If connection to a 1.1 client will be closed, inform client
if (self._request_start_line.version == "HTTP/1.1"
and self._disconnect_on_finish):
headers["Connection"] = "close"
# If a 1.0 client asked for keep-alive, add the header.
if (self._request_start_line.version == "HTTP/1.0"
and self._request_headers.get("Connection",
"").lower() == "keep-alive"):
headers["Connection"] = "Keep-Alive"
if self._chunking_output:
headers["Transfer-Encoding"] = "chunked"
if not self.is_client and (self._request_start_line.method == "HEAD"
or cast(httputil.ResponseStartLine,
start_line).code == 304):
self._expected_content_remaining = 0
elif "Content-Length" in headers:
self._expected_content_remaining = int(headers["Content-Length"])
else:
self._expected_content_remaining = None
# TODO: headers are supposed to be of type str, but we still have some
# cases that let bytes slip through. Remove these native_str calls when those
# are fixed.
header_lines = (native_str(n) + ": " + native_str(v)
for n, v in headers.get_all())
lines.extend(l.encode("latin1") for l in header_lines)
for line in lines:
if b"\n" in line:
raise ValueError("Newline in header: " + repr(line))
future = None
if self.stream.closed():
future = self._write_future = Future()
future.set_exception(iostream.StreamClosedError())
future.exception()
else:
future = self._write_future = Future()
data = b"\r\n".join(lines) + b"\r\n\r\n"
if chunk:
data += self._format_chunk(chunk)
self._pending_write = self.stream.write(data)
future_add_done_callback(self._pending_write,
self._on_write_complete)
return future
def _format_chunk(self, chunk: bytes) -> bytes:
if self._expected_content_remaining is not None:
self._expected_content_remaining -= len(chunk)
if self._expected_content_remaining < 0:
# Close the stream now to stop further framing errors.
self.stream.close()
raise httputil.HTTPOutputError(
"Tried to write more data than Content-Length")
if self._chunking_output and chunk:
# Don't write out empty chunks because that means END-OF-STREAM
# with chunked encoding
return utf8("%x" % len(chunk)) + b"\r\n" + chunk + b"\r\n"
else:
return chunk
def write(self, chunk: bytes) -> "Future[None]":
"""Implements `.HTTPConnection.write`.
For backwards compatibility it is allowed but deprecated to
skip `write_headers` and instead call `write()` with a
pre-encoded header block.
"""
future = None
if self.stream.closed():
future = self._write_future = Future()
self._write_future.set_exception(iostream.StreamClosedError())
self._write_future.exception()
else:
future = self._write_future = Future()
self._pending_write = self.stream.write(self._format_chunk(chunk))
future_add_done_callback(self._pending_write,
self._on_write_complete)
return future
def finish(self) -> None:
"""Implements `.HTTPConnection.finish`."""
if (self._expected_content_remaining is not None
and self._expected_content_remaining != 0
and not self.stream.closed()):
self.stream.close()
raise httputil.HTTPOutputError(
"Tried to write %d bytes less than Content-Length" %
self._expected_content_remaining)
if self._chunking_output:
if not self.stream.closed():
self._pending_write = self.stream.write(b"0\r\n\r\n")
self._pending_write.add_done_callback(self._on_write_complete)
self._write_finished = True
# If the app finished the request while we're still reading,
# divert any remaining data away from the delegate and
# close the connection when we're done sending our response.
# Closing the connection is the only way to avoid reading the
# whole input body.
if not self._read_finished:
self._disconnect_on_finish = True
# No more data is coming, so instruct TCP to send any remaining
# data immediately instead of waiting for a full packet or ack.
self.stream.set_nodelay(True)
if self._pending_write is None:
self._finish_request(None)
else:
future_add_done_callback(self._pending_write, self._finish_request)
def _on_write_complete(self, future: "Future[None]") -> None:
exc = future.exception()
if exc is not None and not isinstance(exc, iostream.StreamClosedError):
future.result()
if self._write_callback is not None:
callback = self._write_callback
self._write_callback = None
self.stream.io_loop.add_callback(callback)
if self._write_future is not None:
future = self._write_future
self._write_future = None
future_set_result_unless_cancelled(future, None)
def _can_keep_alive(self, start_line: httputil.RequestStartLine,
headers: httputil.HTTPHeaders) -> bool:
if self.params.no_keep_alive:
return False
connection_header = headers.get("Connection")
if connection_header is not None:
connection_header = connection_header.lower()
if start_line.version == "HTTP/1.1":
return connection_header != "close"
elif ("Content-Length" in headers
or headers.get("Transfer-Encoding", "").lower() == "chunked"
or getattr(start_line, "method", None) in ("HEAD", "GET")):
# start_line may be a request or response start line; only
# the former has a method attribute.
return connection_header == "keep-alive"
return False
def _finish_request(self, future: "Optional[Future[None]]") -> None:
self._clear_callbacks()
if not self.is_client and self._disconnect_on_finish:
self.close()
return
# Turn Nagle's algorithm back on, leaving the stream in its
# default state for the next request.
self.stream.set_nodelay(False)
if not self._finish_future.done():
future_set_result_unless_cancelled(self._finish_future, None)
def _parse_headers(self, data: bytes) -> Tuple[str, httputil.HTTPHeaders]:
# The lstrip removes newlines that some implementations sometimes
# insert between messages of a reused connection. Per RFC 7230,
# we SHOULD ignore at least one empty line before the request.
# http://tools.ietf.org/html/rfc7230#section-3.5
data_str = native_str(data.decode("latin1")).lstrip("\r\n")
# RFC 7230 section allows for both CRLF and bare LF.
eol = data_str.find("\n")
start_line = data_str[:eol].rstrip("\r")
headers = httputil.HTTPHeaders.parse(data_str[eol:])
return start_line, headers
def _read_body(
self,
code: int,
headers: httputil.HTTPHeaders,
delegate: httputil.HTTPMessageDelegate,
) -> Optional[Awaitable[None]]:
if "Content-Length" in headers:
if "Transfer-Encoding" in headers:
# Response cannot contain both Content-Length and
# Transfer-Encoding headers.
# http://tools.ietf.org/html/rfc7230#section-3.3.3
raise httputil.HTTPInputError(
"Response with both Transfer-Encoding and Content-Length")
if "," in headers["Content-Length"]:
# Proxies sometimes cause Content-Length headers to get
# duplicated. If all the values are identical then we can
# use them but if they differ it's an error.
pieces = re.split(r",\s*", headers["Content-Length"])
if any(i != pieces[0] for i in pieces):
raise httputil.HTTPInputError(
"Multiple unequal Content-Lengths: %r" %
headers["Content-Length"])
headers["Content-Length"] = pieces[0]
try:
content_length = int(
headers["Content-Length"]) # type: Optional[int]
except ValueError:
# Handles non-integer Content-Length value.
raise httputil.HTTPInputError(
"Only integer Content-Length is allowed: %s" %
headers["Content-Length"])
if cast(int, content_length) > self._max_body_size:
raise httputil.HTTPInputError("Content-Length too long")
else:
content_length = None
if code == 204:
# This response code is not allowed to have a non-empty body,
# and has an implicit length of zero instead of read-until-close.
# http://www.w3.org/Protocols/rfc2616/rfc2616-sec4.html#sec4.3
if "Transfer-Encoding" in headers or content_length not in (None,
0):
raise httputil.HTTPInputError(
"Response with code %d should not have body" % code)
content_length = 0
if content_length is not None:
return self._read_fixed_body(content_length, delegate)
if headers.get("Transfer-Encoding", "").lower() == "chunked":
return self._read_chunked_body(delegate)
if self.is_client:
return self._read_body_until_close(delegate)
return None
async def _read_fixed_body(self, content_length: int,
delegate: httputil.HTTPMessageDelegate) -> None:
while content_length > 0:
body = await self.stream.read_bytes(min(self.params.chunk_size,
content_length),
partial=True)
content_length -= len(body)
if not self._write_finished or self.is_client:
with _ExceptionLoggingContext(app_log):
ret = delegate.data_received(body)
if ret is not None:
await ret
async def _read_chunked_body(
self, delegate: httputil.HTTPMessageDelegate) -> None:
# TODO: "chunk extensions" http://tools.ietf.org/html/rfc2616#section-3.6.1
total_size = 0
while True:
chunk_len_str = await self.stream.read_until(b"\r\n", max_bytes=64)
chunk_len = int(chunk_len_str.strip(), 16)
if chunk_len == 0:
crlf = await self.stream.read_bytes(2)
if crlf != b"\r\n":
raise httputil.HTTPInputError(
"improperly terminated chunked request")
return
total_size += chunk_len
if total_size > self._max_body_size:
raise httputil.HTTPInputError("chunked body too large")
bytes_to_read = chunk_len
while bytes_to_read:
chunk = await self.stream.read_bytes(min(
bytes_to_read, self.params.chunk_size),
partial=True)
bytes_to_read -= len(chunk)
if not self._write_finished or self.is_client:
with _ExceptionLoggingContext(app_log):
ret = delegate.data_received(chunk)
if ret is not None:
await ret
# chunk ends with \r\n
crlf = await self.stream.read_bytes(2)
assert crlf == b"\r\n"
async def _read_body_until_close(
self, delegate: httputil.HTTPMessageDelegate) -> None:
body = await self.stream.read_until_close()
if not self._write_finished or self.is_client:
with _ExceptionLoggingContext(app_log):
ret = delegate.data_received(body)
if ret is not None:
await ret
class Runner(object):
"""Internal implementation of `tornado.gen.coroutine`.
Maintains information about pending callbacks and their results.
The results of the generator are stored in ``result_future`` (a
`.Future`)
"""
def __init__(
self,
gen: "Generator[_Yieldable, Any, _T]",
result_future: "Future[_T]",
first_yielded: _Yieldable,
) -> None:
self.gen = gen
self.result_future = result_future
self.future = _null_future # type: Union[None, Future]
self.running = False
self.finished = False
self.io_loop = IOLoop.current()
if self.handle_yield(first_yielded):
gen = result_future = first_yielded = None # type: ignore
self.run()
def run(self) -> None:
"""Starts or resumes the generator, running until it reaches a
yield point that is not ready.
"""
if self.running or self.finished:
return
try:
self.running = True
while True:
future = self.future
if future is None:
raise Exception("No pending future")
if not future.done():
return
self.future = None
try:
exc_info = None
try:
value = future.result()
except Exception:
exc_info = sys.exc_info()
future = None
if exc_info is not None:
try:
yielded = self.gen.throw(*exc_info) # type: ignore
finally:
# Break up a reference to itself
# for faster GC on CPython.
exc_info = None
else:
yielded = self.gen.send(value)
except (StopIteration, Return) as e:
self.finished = True
self.future = _null_future
future_set_result_unless_cancelled(
self.result_future, _value_from_stopiteration(e)
)
self.result_future = None # type: ignore
return
except Exception:
self.finished = True
self.future = _null_future
future_set_exc_info(self.result_future, sys.exc_info())
self.result_future = None # type: ignore
return
if not self.handle_yield(yielded):
return
yielded = None
finally:
self.running = False
def handle_yield(self, yielded: _Yieldable) -> bool:
try:
self.future = convert_yielded(yielded)
except BadYieldError:
self.future = Future()
future_set_exc_info(self.future, sys.exc_info())
if self.future is moment:
self.io_loop.add_callback(self.run)
return False
elif self.future is None:
raise Exception("no pending future")
elif not self.future.done():
def inner(f: Any) -> None:
# Break a reference cycle to speed GC.
f = None # noqa: F841
self.run()
self.io_loop.add_future(self.future, inner)
return False
return True
def handle_exception(
self, typ: Type[Exception], value: Exception, tb: types.TracebackType
) -> bool:
if not self.running and not self.finished:
self.future = Future()
future_set_exc_info(self.future, (typ, value, tb))
self.run()
return True
else:
return False
class WaitIterator(object):
"""Provides an iterator to yield the results of awaitables as they finish.
Yielding a set of awaitables like this:
``results = yield [awaitable1, awaitable2]``
pauses the coroutine until both ``awaitable1`` and ``awaitable2``
return, and then restarts the coroutine with the results of both
awaitables. If either awaitable raises an exception, the
expression will raise that exception and all the results will be
lost.
If you need to get the result of each awaitable as soon as possible,
or if you need the result of some awaitables even if others produce
errors, you can use ``WaitIterator``::
wait_iterator = gen.WaitIterator(awaitable1, awaitable2)
while not wait_iterator.done():
try:
result = yield wait_iterator.next()
except Exception as e:
print("Error {} from {}".format(e, wait_iterator.current_future))
else:
print("Result {} received from {} at {}".format(
result, wait_iterator.current_future,
wait_iterator.current_index))
Because results are returned as soon as they are available the
output from the iterator *will not be in the same order as the
input arguments*. If you need to know which future produced the
current result, you can use the attributes
``WaitIterator.current_future``, or ``WaitIterator.current_index``
to get the index of the awaitable from the input list. (if keyword
arguments were used in the construction of the `WaitIterator`,
``current_index`` will use the corresponding keyword).
On Python 3.5, `WaitIterator` implements the async iterator
protocol, so it can be used with the ``async for`` statement (note
that in this version the entire iteration is aborted if any value
raises an exception, while the previous example can continue past
individual errors)::
async for result in gen.WaitIterator(future1, future2):
print("Result {} received from {} at {}".format(
result, wait_iterator.current_future,
wait_iterator.current_index))
.. versionadded:: 4.1
.. versionchanged:: 4.3
Added ``async for`` support in Python 3.5.
"""
_unfinished = {} # type: Dict[Future, Union[int, str]]
def __init__(self, *args: Future, **kwargs: Future) -> None:
if args and kwargs:
raise ValueError("You must provide args or kwargs, not both")
if kwargs:
self._unfinished = dict((f, k) for (k, f) in kwargs.items())
futures = list(kwargs.values()) # type: Sequence[Future]
else:
self._unfinished = dict((f, i) for (i, f) in enumerate(args))
futures = args
self._finished = collections.deque() # type: Deque[Future]
self.current_index = None # type: Optional[Union[str, int]]
self.current_future = None # type: Optional[Future]
self._running_future = None # type: Optional[Future]
for future in futures:
future_add_done_callback(future, self._done_callback)
def done(self) -> bool:
"""Returns True if this iterator has no more results."""
if self._finished or self._unfinished:
return False
# Clear the 'current' values when iteration is done.
self.current_index = self.current_future = None
return True
def next(self) -> Future:
"""Returns a `.Future` that will yield the next available result.
Note that this `.Future` will not be the same object as any of
the inputs.
"""
self._running_future = Future()
if self._finished:
self._return_result(self._finished.popleft())
return self._running_future
def _done_callback(self, done: Future) -> None:
if self._running_future and not self._running_future.done():
self._return_result(done)
else:
self._finished.append(done)
def _return_result(self, done: Future) -> None:
"""Called set the returned future's state that of the future
we yielded, and set the current future for the iterator.
"""
if self._running_future is None:
raise Exception("no future is running")
chain_future(done, self._running_future)
self.current_future = done
self.current_index = self._unfinished.pop(done)
def __aiter__(self) -> typing.AsyncIterator:
return self
def __anext__(self) -> Future:
if self.done():
# Lookup by name to silence pyflakes on older versions.
raise getattr(builtins, "StopAsyncIteration")()
return self.next()
