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.. _aiohttp-web-lowlevel: |
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Low Level Server |
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================ |
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.. currentmodule:: aiohttp.web |
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This topic describes :mod:`aiohttp.web` based *low level* API. |
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Abstract |
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-------- |
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Sometimes user don't need high-level concepts introduced in |
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:ref:`aiohttp-web`: applications, routers, middlewares and signals. |
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All what is needed is supporting asynchronous callable which accepts a |
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request and returns a response object. |
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This is done by introducing :class:`aiohttp.web.Server` class which |
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serves a *protocol factory* role for |
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:meth:`asyncio.loop.create_server` and bridges data |
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stream to *web handler* and sends result back. |
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Low level *web handler* should accept the single :class:`BaseRequest` |
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parameter and performs one of the following actions: |
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1. Return a :class:`Response` with the whole HTTP body stored in memory. |
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2. Create a :class:`StreamResponse`, send headers by |
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:meth:`StreamResponse.prepare` call, send data chunks by |
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:meth:`StreamResponse.write` and return finished response. |
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3. Raise :class:`HTTPException` derived exception (see |
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:ref:`aiohttp-web-exceptions` section). |
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All other exceptions not derived from :class:`HTTPException` |
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leads to *500 Internal Server Error* response. |
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4. Initiate and process Web-Socket connection by |
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:class:`WebSocketResponse` using (see :ref:`aiohttp-web-websockets`). |
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Run a Basic Low-Level Server |
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---------------------------- |
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The following code demonstrates very trivial usage example:: |
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import asyncio |
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from aiohttp import web |
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async def handler(request): |
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return web.Response(text="OK") |
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async def main(): |
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server = web.Server(handler) |
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runner = web.ServerRunner(server) |
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await runner.setup() |
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site = web.TCPSite(runner, 'localhost', 8080) |
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await site.start() |
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print("======= Serving on http://127.0.0.1:8080/ ======") |
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# pause here for very long time by serving HTTP requests and |
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# waiting for keyboard interruption |
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await asyncio.sleep(100*3600) |
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asyncio.run(main()) |
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In the snippet we have ``handler`` which returns a regular |
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:class:`Response` with ``"OK"`` in BODY. |
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This *handler* is processed by ``server`` (:class:`Server` which acts |
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as *protocol factory*). Network communication is created by |
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:ref:`runners API <aiohttp-web-app-runners-reference>` to serve |
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``http://127.0.0.1:8080/``. |
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The handler should process every request for every *path*, e.g. |
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``GET``, ``POST``, Web-Socket. |
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The example is very basic: it always return ``200 OK`` response, real |
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life code is much more complex usually. |
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