Update 2025-04-24_11:44:19
This commit is contained in:
oib
@ -0,0 +1,708 @@
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"""
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Support for streaming http requests in emscripten.
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A few caveats -
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If your browser (or Node.js) has WebAssembly JavaScript Promise Integration enabled
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https://github.com/WebAssembly/js-promise-integration/blob/main/proposals/js-promise-integration/Overview.md
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*and* you launch pyodide using `pyodide.runPythonAsync`, this will fetch data using the
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JavaScript asynchronous fetch api (wrapped via `pyodide.ffi.call_sync`). In this case
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timeouts and streaming should just work.
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Otherwise, it uses a combination of XMLHttpRequest and a web-worker for streaming.
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This approach has several caveats:
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Firstly, you can't do streaming http in the main UI thread, because atomics.wait isn't allowed.
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Streaming only works if you're running pyodide in a web worker.
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Secondly, this uses an extra web worker and SharedArrayBuffer to do the asynchronous fetch
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operation, so it requires that you have crossOriginIsolation enabled, by serving over https
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(or from localhost) with the two headers below set:
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Cross-Origin-Opener-Policy: same-origin
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Cross-Origin-Embedder-Policy: require-corp
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You can tell if cross origin isolation is successfully enabled by looking at the global crossOriginIsolated variable in
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JavaScript console. If it isn't, streaming requests will fallback to XMLHttpRequest, i.e. getting the whole
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request into a buffer and then returning it. it shows a warning in the JavaScript console in this case.
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Finally, the webworker which does the streaming fetch is created on initial import, but will only be started once
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control is returned to javascript. Call `await wait_for_streaming_ready()` to wait for streaming fetch.
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NB: in this code, there are a lot of JavaScript objects. They are named js_*
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to make it clear what type of object they are.
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"""
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from __future__ import annotations
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import io
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import json
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from email.parser import Parser
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from importlib.resources import files
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from typing import TYPE_CHECKING, Any
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import js # type: ignore[import-not-found]
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from pyodide.ffi import ( # type: ignore[import-not-found]
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JsArray,
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JsException,
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JsProxy,
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to_js,
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)
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if TYPE_CHECKING:
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from typing_extensions import Buffer
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from .request import EmscriptenRequest
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from .response import EmscriptenResponse
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"""
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There are some headers that trigger unintended CORS preflight requests.
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See also https://github.com/koenvo/pyodide-http/issues/22
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"""
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HEADERS_TO_IGNORE = ("user-agent",)
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SUCCESS_HEADER = -1
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SUCCESS_EOF = -2
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ERROR_TIMEOUT = -3
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ERROR_EXCEPTION = -4
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_STREAMING_WORKER_CODE = (
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files(__package__)
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.joinpath("emscripten_fetch_worker.js")
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.read_text(encoding="utf-8")
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)
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class _RequestError(Exception):
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def __init__(
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self,
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message: str | None = None,
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*,
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request: EmscriptenRequest | None = None,
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response: EmscriptenResponse | None = None,
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):
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self.request = request
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self.response = response
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self.message = message
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super().__init__(self.message)
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class _StreamingError(_RequestError):
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pass
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class _TimeoutError(_RequestError):
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pass
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def _obj_from_dict(dict_val: dict[str, Any]) -> JsProxy:
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return to_js(dict_val, dict_converter=js.Object.fromEntries)
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class _ReadStream(io.RawIOBase):
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def __init__(
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self,
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int_buffer: JsArray,
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byte_buffer: JsArray,
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timeout: float,
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worker: JsProxy,
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connection_id: int,
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request: EmscriptenRequest,
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):
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self.int_buffer = int_buffer
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self.byte_buffer = byte_buffer
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self.read_pos = 0
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self.read_len = 0
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self.connection_id = connection_id
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self.worker = worker
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self.timeout = int(1000 * timeout) if timeout > 0 else None
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self.is_live = True
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self._is_closed = False
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self.request: EmscriptenRequest | None = request
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def __del__(self) -> None:
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self.close()
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# this is compatible with _base_connection
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def is_closed(self) -> bool:
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return self._is_closed
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# for compatibility with RawIOBase
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@property
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def closed(self) -> bool:
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return self.is_closed()
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def close(self) -> None:
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if self.is_closed():
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return
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self.read_len = 0
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self.read_pos = 0
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self.int_buffer = None
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self.byte_buffer = None
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self._is_closed = True
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self.request = None
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if self.is_live:
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self.worker.postMessage(_obj_from_dict({"close": self.connection_id}))
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self.is_live = False
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super().close()
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def readable(self) -> bool:
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return True
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def writable(self) -> bool:
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return False
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def seekable(self) -> bool:
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return False
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def readinto(self, byte_obj: Buffer) -> int:
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if not self.int_buffer:
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raise _StreamingError(
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"No buffer for stream in _ReadStream.readinto",
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request=self.request,
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response=None,
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)
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if self.read_len == 0:
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# wait for the worker to send something
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js.Atomics.store(self.int_buffer, 0, ERROR_TIMEOUT)
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self.worker.postMessage(_obj_from_dict({"getMore": self.connection_id}))
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if (
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js.Atomics.wait(self.int_buffer, 0, ERROR_TIMEOUT, self.timeout)
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== "timed-out"
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):
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raise _TimeoutError
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data_len = self.int_buffer[0]
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if data_len > 0:
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self.read_len = data_len
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self.read_pos = 0
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elif data_len == ERROR_EXCEPTION:
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string_len = self.int_buffer[1]
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# decode the error string
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js_decoder = js.TextDecoder.new()
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json_str = js_decoder.decode(self.byte_buffer.slice(0, string_len))
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raise _StreamingError(
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f"Exception thrown in fetch: {json_str}",
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request=self.request,
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response=None,
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)
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else:
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# EOF, free the buffers and return zero
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# and free the request
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self.is_live = False
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self.close()
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return 0
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# copy from int32array to python bytes
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ret_length = min(self.read_len, len(memoryview(byte_obj)))
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subarray = self.byte_buffer.subarray(
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self.read_pos, self.read_pos + ret_length
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).to_py()
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memoryview(byte_obj)[0:ret_length] = subarray
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self.read_len -= ret_length
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self.read_pos += ret_length
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return ret_length
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class _StreamingFetcher:
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def __init__(self) -> None:
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# make web-worker and data buffer on startup
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self.streaming_ready = False
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js_data_blob = js.Blob.new(
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to_js([_STREAMING_WORKER_CODE], create_pyproxies=False),
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_obj_from_dict({"type": "application/javascript"}),
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)
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def promise_resolver(js_resolve_fn: JsProxy, js_reject_fn: JsProxy) -> None:
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def onMsg(e: JsProxy) -> None:
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self.streaming_ready = True
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js_resolve_fn(e)
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def onErr(e: JsProxy) -> None:
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js_reject_fn(e) # Defensive: never happens in ci
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self.js_worker.onmessage = onMsg
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self.js_worker.onerror = onErr
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js_data_url = js.URL.createObjectURL(js_data_blob)
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self.js_worker = js.globalThis.Worker.new(js_data_url)
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self.js_worker_ready_promise = js.globalThis.Promise.new(promise_resolver)
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def send(self, request: EmscriptenRequest) -> EmscriptenResponse:
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headers = {
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k: v for k, v in request.headers.items() if k not in HEADERS_TO_IGNORE
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}
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body = request.body
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fetch_data = {"headers": headers, "body": to_js(body), "method": request.method}
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# start the request off in the worker
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timeout = int(1000 * request.timeout) if request.timeout > 0 else None
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js_shared_buffer = js.SharedArrayBuffer.new(1048576)
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js_int_buffer = js.Int32Array.new(js_shared_buffer)
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js_byte_buffer = js.Uint8Array.new(js_shared_buffer, 8)
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js.Atomics.store(js_int_buffer, 0, ERROR_TIMEOUT)
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js.Atomics.notify(js_int_buffer, 0)
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js_absolute_url = js.URL.new(request.url, js.location).href
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self.js_worker.postMessage(
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_obj_from_dict(
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{
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"buffer": js_shared_buffer,
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"url": js_absolute_url,
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"fetchParams": fetch_data,
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}
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)
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)
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# wait for the worker to send something
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js.Atomics.wait(js_int_buffer, 0, ERROR_TIMEOUT, timeout)
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if js_int_buffer[0] == ERROR_TIMEOUT:
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raise _TimeoutError(
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"Timeout connecting to streaming request",
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request=request,
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response=None,
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)
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elif js_int_buffer[0] == SUCCESS_HEADER:
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# got response
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# header length is in second int of intBuffer
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string_len = js_int_buffer[1]
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# decode the rest to a JSON string
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js_decoder = js.TextDecoder.new()
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# this does a copy (the slice) because decode can't work on shared array
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# for some silly reason
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json_str = js_decoder.decode(js_byte_buffer.slice(0, string_len))
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# get it as an object
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response_obj = json.loads(json_str)
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return EmscriptenResponse(
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request=request,
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status_code=response_obj["status"],
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headers=response_obj["headers"],
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body=_ReadStream(
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js_int_buffer,
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js_byte_buffer,
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request.timeout,
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self.js_worker,
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response_obj["connectionID"],
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request,
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),
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)
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elif js_int_buffer[0] == ERROR_EXCEPTION:
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string_len = js_int_buffer[1]
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# decode the error string
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js_decoder = js.TextDecoder.new()
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json_str = js_decoder.decode(js_byte_buffer.slice(0, string_len))
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raise _StreamingError(
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f"Exception thrown in fetch: {json_str}", request=request, response=None
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)
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else:
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raise _StreamingError(
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f"Unknown status from worker in fetch: {js_int_buffer[0]}",
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request=request,
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response=None,
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)
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class _JSPIReadStream(io.RawIOBase):
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"""
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A read stream that uses pyodide.ffi.run_sync to read from a JavaScript fetch
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response. This requires support for WebAssembly JavaScript Promise Integration
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in the containing browser, and for pyodide to be launched via runPythonAsync.
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:param js_read_stream:
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The JavaScript stream reader
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:param timeout:
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Timeout in seconds
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:param request:
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The request we're handling
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:param response:
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The response this stream relates to
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:param js_abort_controller:
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A JavaScript AbortController object, used for timeouts
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"""
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def __init__(
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self,
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js_read_stream: Any,
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timeout: float,
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request: EmscriptenRequest,
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response: EmscriptenResponse,
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js_abort_controller: Any, # JavaScript AbortController for timeouts
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):
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self.js_read_stream = js_read_stream
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self.timeout = timeout
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self._is_closed = False
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self._is_done = False
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self.request: EmscriptenRequest | None = request
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self.response: EmscriptenResponse | None = response
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self.current_buffer = None
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self.current_buffer_pos = 0
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self.js_abort_controller = js_abort_controller
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def __del__(self) -> None:
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self.close()
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# this is compatible with _base_connection
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def is_closed(self) -> bool:
|
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return self._is_closed
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||||
|
||||
# for compatibility with RawIOBase
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@property
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||||
def closed(self) -> bool:
|
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return self.is_closed()
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||||
|
||||
def close(self) -> None:
|
||||
if self.is_closed():
|
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return
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self.read_len = 0
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self.read_pos = 0
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self.js_read_stream.cancel()
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self.js_read_stream = None
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self._is_closed = True
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||||
self._is_done = True
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||||
self.request = None
|
||||
self.response = None
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||||
super().close()
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||||
|
||||
def readable(self) -> bool:
|
||||
return True
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||||
|
||||
def writable(self) -> bool:
|
||||
return False
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||||
|
||||
def seekable(self) -> bool:
|
||||
return False
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|
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def _get_next_buffer(self) -> bool:
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result_js = _run_sync_with_timeout(
|
||||
self.js_read_stream.read(),
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self.timeout,
|
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self.js_abort_controller,
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request=self.request,
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||||
response=self.response,
|
||||
)
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||||
if result_js.done:
|
||||
self._is_done = True
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return False
|
||||
else:
|
||||
self.current_buffer = result_js.value.to_py()
|
||||
self.current_buffer_pos = 0
|
||||
return True
|
||||
|
||||
def readinto(self, byte_obj: Buffer) -> int:
|
||||
if self.current_buffer is None:
|
||||
if not self._get_next_buffer() or self.current_buffer is None:
|
||||
self.close()
|
||||
return 0
|
||||
ret_length = min(
|
||||
len(byte_obj), len(self.current_buffer) - self.current_buffer_pos
|
||||
)
|
||||
byte_obj[0:ret_length] = self.current_buffer[
|
||||
self.current_buffer_pos : self.current_buffer_pos + ret_length
|
||||
]
|
||||
self.current_buffer_pos += ret_length
|
||||
if self.current_buffer_pos == len(self.current_buffer):
|
||||
self.current_buffer = None
|
||||
return ret_length
|
||||
|
||||
|
||||
# check if we are in a worker or not
|
||||
def is_in_browser_main_thread() -> bool:
|
||||
return hasattr(js, "window") and hasattr(js, "self") and js.self == js.window
|
||||
|
||||
|
||||
def is_cross_origin_isolated() -> bool:
|
||||
return hasattr(js, "crossOriginIsolated") and js.crossOriginIsolated
|
||||
|
||||
|
||||
def is_in_node() -> bool:
|
||||
return (
|
||||
hasattr(js, "process")
|
||||
and hasattr(js.process, "release")
|
||||
and hasattr(js.process.release, "name")
|
||||
and js.process.release.name == "node"
|
||||
)
|
||||
|
||||
|
||||
def is_worker_available() -> bool:
|
||||
return hasattr(js, "Worker") and hasattr(js, "Blob")
|
||||
|
||||
|
||||
_fetcher: _StreamingFetcher | None = None
|
||||
|
||||
if is_worker_available() and (
|
||||
(is_cross_origin_isolated() and not is_in_browser_main_thread())
|
||||
and (not is_in_node())
|
||||
):
|
||||
_fetcher = _StreamingFetcher()
|
||||
else:
|
||||
_fetcher = None
|
||||
|
||||
|
||||
NODE_JSPI_ERROR = (
|
||||
"urllib3 only works in Node.js with pyodide.runPythonAsync"
|
||||
" and requires the flag --experimental-wasm-stack-switching in "
|
||||
" versions of node <24."
|
||||
)
|
||||
|
||||
|
||||
def send_streaming_request(request: EmscriptenRequest) -> EmscriptenResponse | None:
|
||||
if has_jspi():
|
||||
return send_jspi_request(request, True)
|
||||
elif is_in_node():
|
||||
raise _RequestError(
|
||||
message=NODE_JSPI_ERROR,
|
||||
request=request,
|
||||
response=None,
|
||||
)
|
||||
|
||||
if _fetcher and streaming_ready():
|
||||
return _fetcher.send(request)
|
||||
else:
|
||||
_show_streaming_warning()
|
||||
return None
|
||||
|
||||
|
||||
_SHOWN_TIMEOUT_WARNING = False
|
||||
|
||||
|
||||
def _show_timeout_warning() -> None:
|
||||
global _SHOWN_TIMEOUT_WARNING
|
||||
if not _SHOWN_TIMEOUT_WARNING:
|
||||
_SHOWN_TIMEOUT_WARNING = True
|
||||
message = "Warning: Timeout is not available on main browser thread"
|
||||
js.console.warn(message)
|
||||
|
||||
|
||||
_SHOWN_STREAMING_WARNING = False
|
||||
|
||||
|
||||
def _show_streaming_warning() -> None:
|
||||
global _SHOWN_STREAMING_WARNING
|
||||
if not _SHOWN_STREAMING_WARNING:
|
||||
_SHOWN_STREAMING_WARNING = True
|
||||
message = "Can't stream HTTP requests because: \n"
|
||||
if not is_cross_origin_isolated():
|
||||
message += " Page is not cross-origin isolated\n"
|
||||
if is_in_browser_main_thread():
|
||||
message += " Python is running in main browser thread\n"
|
||||
if not is_worker_available():
|
||||
message += " Worker or Blob classes are not available in this environment." # Defensive: this is always False in browsers that we test in
|
||||
if streaming_ready() is False:
|
||||
message += """ Streaming fetch worker isn't ready. If you want to be sure that streaming fetch
|
||||
is working, you need to call: 'await urllib3.contrib.emscripten.fetch.wait_for_streaming_ready()`"""
|
||||
from js import console
|
||||
|
||||
console.warn(message)
|
||||
|
||||
|
||||
def send_request(request: EmscriptenRequest) -> EmscriptenResponse:
|
||||
if has_jspi():
|
||||
return send_jspi_request(request, False)
|
||||
elif is_in_node():
|
||||
raise _RequestError(
|
||||
message=NODE_JSPI_ERROR,
|
||||
request=request,
|
||||
response=None,
|
||||
)
|
||||
try:
|
||||
js_xhr = js.XMLHttpRequest.new()
|
||||
|
||||
if not is_in_browser_main_thread():
|
||||
js_xhr.responseType = "arraybuffer"
|
||||
if request.timeout:
|
||||
js_xhr.timeout = int(request.timeout * 1000)
|
||||
else:
|
||||
js_xhr.overrideMimeType("text/plain; charset=ISO-8859-15")
|
||||
if request.timeout:
|
||||
# timeout isn't available on the main thread - show a warning in console
|
||||
# if it is set
|
||||
_show_timeout_warning()
|
||||
|
||||
js_xhr.open(request.method, request.url, False)
|
||||
for name, value in request.headers.items():
|
||||
if name.lower() not in HEADERS_TO_IGNORE:
|
||||
js_xhr.setRequestHeader(name, value)
|
||||
|
||||
js_xhr.send(to_js(request.body))
|
||||
|
||||
headers = dict(Parser().parsestr(js_xhr.getAllResponseHeaders()))
|
||||
|
||||
if not is_in_browser_main_thread():
|
||||
body = js_xhr.response.to_py().tobytes()
|
||||
else:
|
||||
body = js_xhr.response.encode("ISO-8859-15")
|
||||
return EmscriptenResponse(
|
||||
status_code=js_xhr.status, headers=headers, body=body, request=request
|
||||
)
|
||||
except JsException as err:
|
||||
if err.name == "TimeoutError":
|
||||
raise _TimeoutError(err.message, request=request)
|
||||
elif err.name == "NetworkError":
|
||||
raise _RequestError(err.message, request=request)
|
||||
else:
|
||||
# general http error
|
||||
raise _RequestError(err.message, request=request)
|
||||
|
||||
|
||||
def send_jspi_request(
|
||||
request: EmscriptenRequest, streaming: bool
|
||||
) -> EmscriptenResponse:
|
||||
"""
|
||||
Send a request using WebAssembly JavaScript Promise Integration
|
||||
to wrap the asynchronous JavaScript fetch api (experimental).
|
||||
|
||||
:param request:
|
||||
Request to send
|
||||
|
||||
:param streaming:
|
||||
Whether to stream the response
|
||||
|
||||
:return: The response object
|
||||
:rtype: EmscriptenResponse
|
||||
"""
|
||||
timeout = request.timeout
|
||||
js_abort_controller = js.AbortController.new()
|
||||
headers = {k: v for k, v in request.headers.items() if k not in HEADERS_TO_IGNORE}
|
||||
req_body = request.body
|
||||
fetch_data = {
|
||||
"headers": headers,
|
||||
"body": to_js(req_body),
|
||||
"method": request.method,
|
||||
"signal": js_abort_controller.signal,
|
||||
}
|
||||
# Call JavaScript fetch (async api, returns a promise)
|
||||
fetcher_promise_js = js.fetch(request.url, _obj_from_dict(fetch_data))
|
||||
# Now suspend WebAssembly until we resolve that promise
|
||||
# or time out.
|
||||
response_js = _run_sync_with_timeout(
|
||||
fetcher_promise_js,
|
||||
timeout,
|
||||
js_abort_controller,
|
||||
request=request,
|
||||
response=None,
|
||||
)
|
||||
headers = {}
|
||||
header_iter = response_js.headers.entries()
|
||||
while True:
|
||||
iter_value_js = header_iter.next()
|
||||
if getattr(iter_value_js, "done", False):
|
||||
break
|
||||
else:
|
||||
headers[str(iter_value_js.value[0])] = str(iter_value_js.value[1])
|
||||
status_code = response_js.status
|
||||
body: bytes | io.RawIOBase = b""
|
||||
|
||||
response = EmscriptenResponse(
|
||||
status_code=status_code, headers=headers, body=b"", request=request
|
||||
)
|
||||
if streaming:
|
||||
# get via inputstream
|
||||
if response_js.body is not None:
|
||||
# get a reader from the fetch response
|
||||
body_stream_js = response_js.body.getReader()
|
||||
body = _JSPIReadStream(
|
||||
body_stream_js, timeout, request, response, js_abort_controller
|
||||
)
|
||||
else:
|
||||
# get directly via arraybuffer
|
||||
# n.b. this is another async JavaScript call.
|
||||
body = _run_sync_with_timeout(
|
||||
response_js.arrayBuffer(),
|
||||
timeout,
|
||||
js_abort_controller,
|
||||
request=request,
|
||||
response=response,
|
||||
).to_py()
|
||||
response.body = body
|
||||
return response
|
||||
|
||||
|
||||
def _run_sync_with_timeout(
|
||||
promise: Any,
|
||||
timeout: float,
|
||||
js_abort_controller: Any,
|
||||
request: EmscriptenRequest | None,
|
||||
response: EmscriptenResponse | None,
|
||||
) -> Any:
|
||||
"""
|
||||
Await a JavaScript promise synchronously with a timeout which is implemented
|
||||
via the AbortController
|
||||
|
||||
:param promise:
|
||||
Javascript promise to await
|
||||
|
||||
:param timeout:
|
||||
Timeout in seconds
|
||||
|
||||
:param js_abort_controller:
|
||||
A JavaScript AbortController object, used on timeout
|
||||
|
||||
:param request:
|
||||
The request being handled
|
||||
|
||||
:param response:
|
||||
The response being handled (if it exists yet)
|
||||
|
||||
:raises _TimeoutError: If the request times out
|
||||
:raises _RequestError: If the request raises a JavaScript exception
|
||||
|
||||
:return: The result of awaiting the promise.
|
||||
"""
|
||||
timer_id = None
|
||||
if timeout > 0:
|
||||
timer_id = js.setTimeout(
|
||||
js_abort_controller.abort.bind(js_abort_controller), int(timeout * 1000)
|
||||
)
|
||||
try:
|
||||
from pyodide.ffi import run_sync
|
||||
|
||||
# run_sync here uses WebAssembly JavaScript Promise Integration to
|
||||
# suspend python until the JavaScript promise resolves.
|
||||
return run_sync(promise)
|
||||
except JsException as err:
|
||||
if err.name == "AbortError":
|
||||
raise _TimeoutError(
|
||||
message="Request timed out", request=request, response=response
|
||||
)
|
||||
else:
|
||||
raise _RequestError(message=err.message, request=request, response=response)
|
||||
finally:
|
||||
if timer_id is not None:
|
||||
js.clearTimeout(timer_id)
|
||||
|
||||
|
||||
def has_jspi() -> bool:
|
||||
"""
|
||||
Return true if jspi can be used.
|
||||
|
||||
This requires both browser support and also WebAssembly
|
||||
to be in the correct state - i.e. that the javascript
|
||||
call into python was async not sync.
|
||||
|
||||
:return: True if jspi can be used.
|
||||
:rtype: bool
|
||||
"""
|
||||
try:
|
||||
from pyodide.ffi import can_run_sync, run_sync # noqa: F401
|
||||
|
||||
return bool(can_run_sync())
|
||||
except ImportError:
|
||||
return False
|
||||
|
||||
|
||||
def streaming_ready() -> bool | None:
|
||||
if _fetcher:
|
||||
return _fetcher.streaming_ready
|
||||
else:
|
||||
return None # no fetcher, return None to signify that
|
||||
|
||||
|
||||
async def wait_for_streaming_ready() -> bool:
|
||||
if _fetcher:
|
||||
await _fetcher.js_worker_ready_promise
|
||||
return True
|
||||
else:
|
||||
return False
|
||||
Reference in New Issue
Block a user