Streaming

Sanic allows you to stream content to the client with the stream method. This method accepts a coroutine callback which is passed a StreamingHTTPResponse object that is written to. A simple example is like follows:

from sanic import Sanic
from sanic.response import stream

app = Sanic(__name__)

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

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

This is useful in situations where you want to stream content to the client that originates in an external service, like a database. For example, you can stream database records to the client with the asynchronous cursor that asyncpg provides:

@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)'):
                response.write(record[0])

    return stream(stream_from_db)