流动

请求流

SANIC允许您通过流获取请求数据,如下所示。当请求结束时,wait request.stream.read()返回none。只有post、put和patch修饰符具有流参数。

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('request_stream')


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。此方法接受一个协程回调,该回调将传递一个写入的streaminghtpResponse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')

这在您希望将内容流式传输到源自外部服务(如数据库)的客户机的情况下非常有用。例如,可以使用AsyncPG提供的异步光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)

如果客户机支持HTTP/1.1,SANIC将使用分块传输编码;您可以使用流函数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,当您想发送一个大文件时,该函数非常有用。它返回streaminghttpresponse对象,并在默认情况下使用分块传输编码;因此,sanic不会在响应中添加内容长度http头。如果要使用此头,可以禁用分块传输编码并手动添加:

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,
    )