Sanic Streaming – 流式传输

我们在Sanic HTTP 响应中已经学习了响应的流式传输。实际上，Sanic还支持请求的流式传输。

请求流

下面的例子，当请求结束，await request.stream.read() 返回 None。只有post, put, patch修饰器有流参数。

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 允许我们使用stream方法向客户端流式传输内容。该方法接受一个带有StreamingHTTPResponse对象参数用以写操作的协程回调函数。比如下面的例子：

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')

这在将源自外部服务（如数据库）的内容流式传输给客户端的情况下非常有用。例如，我们可以使用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)

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