Sanic官翻-流媒体

Posted 2021-05-13 fhkankan

流媒体

请求流

Sanic允许您按流获取请求数据，如下所示。请求结束时，await request.stream.read()返回None。只有post，put和patch装饰器具有stream参数。

from sanic import Sanic
from sanic.views import CompositionView
from sanic.views import HTTPMethodView
from sanic.views import stream as stream_decorator
from sanic.blueprints import Blueprint
from sanic.response import stream, text

bp = Blueprint(\'blueprint_request_stream\')
app = Sanic(__name__)


class SimpleView(HTTPMethodView):

    @stream_decorator
    async def post(self, request):
        result = \'\'
        while True:
            body = await request.stream.read()
            if body is None:
                break
            result += body.decode(\'utf-8\')
        return text(result)


@app.post(\'/stream\', stream=True)
async def handler(request):
    async def streaming(response):
        while True:
            body = await request.stream.read()
            if body is None:
                break
            body = body.decode(\'utf-8\').replace(\'1\', \'A\')
            await response.write(body)
    return stream(streaming)


@bp.put(\'/bp_stream\', stream=True)
async def bp_put_handler(request):
    result = \'\'
    while True:
        body = await request.stream.read()
        if body is None:
            break
        result += body.decode(\'utf-8\').replace(\'1\', \'A\')
    return text(result)


# You can also use `bp.add_route()` with stream argument
async def bp_post_handler(request):
    result = \'\'
    while True:
        body = await request.stream.read()
        if body is None:
            break
        result += body.decode(\'utf-8\').replace(\'1\', \'A\')
    return text(result)

bp.add_route(bp_post_handler, \'/bp_stream\', methods=[\'POST\'], stream=True)


async def post_handler(request):
    result = \'\'
    while True:
        body = await request.stream.read()
        if body is None:
            break
        result += body.decode(\'utf-8\')
    return text(result)

app.blueprint(bp)
app.add_route(SimpleView.as_view(), \'/method_view\')
view = CompositionView()
view.add([\'POST\'], post_handler, stream=True)
app.add_route(view, \'/composition_view\')


if __name__ == \'__main__\':
    app.run(host=\'127.0.0.1\', port=8000)

响应流

Sanic允许您使用stream方法将内容流式传输到客户端。此方法接受协程回调，该回调传递给写入的StreamingHTTPResponse对象。一个简单的例子如下：

from sanic import Sanic
from sanic.response import stream

app = Sanic(__name__)

@app.route("/")
async def test(request):
    async def sample_streaming_fn(response):
        await response.write(\'foo,\')
        await response.write(\'bar\')

    return stream(sample_streaming_fn, content_type=\'text/csv\')

在要将内容流传输到源自外部服务（例如数据库）的客户端的情况下，这很有用。例如，您可以使用asyncpg提供的异步游标将数据库记录流式传输到客户端：

@app.route("/")
async def index(request):
    async def stream_from_db(response):
        conn = await asyncpg.connect(database=\'test\')
        async with conn.transaction():
            async for record in conn.cursor(\'SELECT generate_series(0, 10)\'):
                await response.write(record[0])

    return stream(stream_from_db)

如果客户端支持HTTP / 1.1，Sanic将使用分块传输编码;；您可以使用流功能的分块选项显式启用或禁用它。

文件流

Sanic提供sanic.response.file_stream函数，该函数在您要发送大文件时很有用。它返回一个StreamingHTTPResponse对象，默认情况下将使用分块传输编码。因此，Sanic不会在响应中添加Content-Length HTTP标头。如果要使用此标头，则可以禁用分块传输编码并手动添加它：

from aiofiles import os as async_os
from sanic.response import file_stream

@app.route("/")
async def index(request):
    file_path = "/srv/www/whatever.png"

    file_stat = await async_os.stat(file_path)
    headers = {"Content-Length": str(file_stat.st_size)}

    return await file_stream(
        file_path,
        headers=headers,
        chunked=False,
    )