之前有過(guò)朋友問(wèn)我Flask巷送、Express這些框架是如何在函數(shù)中運(yùn)行，他是怎么樣的一個(gè)機(jī)制蔓姚？還有人問(wèn)我如何做一個(gè)Component惕耕？看了一下騰訊云Serverless架構(gòu)現(xiàn)在支持的框架：
我發(fā)現(xiàn)雖然支持了很多躏嚎，但是我比較鐘愛(ài)的Django貌似沒(méi)有蜜自，正好想到了部分人的疑惑，所以在這里卢佣，我就簡(jiǎn)單的和大家說(shuō)一下重荠，我如何做一個(gè)Django的Component。
分析已有Component（Flask為例）
首先第一步虚茶，我們要知道其他的框架是怎么運(yùn)行的戈鲁，例如Flask等，我們先通過(guò)騰訊云的Flask-Component嘹叫，按照他的說(shuō)明部署一下：
非常簡(jiǎn)單輕松愉快的部署上線婆殿，然后在函數(shù)的控制臺(tái)，我們把部署好的下載下來(lái)罩扇，研究一下：
下載解壓之后鸣皂，我們可以看這樣一個(gè)目錄結(jié)構(gòu)：
藍(lán)色框起來(lái)的，是依賴包暮蹂，黃色的app.py是我們的自己寫的代碼寞缝，那么紅色圈起來(lái)的是什么？這兩個(gè)文件從哪里出來(lái)的仰泻？
api_server.py文件內(nèi)容：
import app # Replace with your actual application
import severless_wsgi
# If you need to send additional content types as text, add then directly
# to the whitelist:
#
# serverless_wsgi.TEXT_MIME_TYPES.append("application/custom+json")
def handler(event, context):
return severless_wsgi.handle_request(app.app, event, context)
可以看到荆陆，這里面是將我們創(chuàng)建的app.py文件引入，并且拿到了app這個(gè)對(duì)象集侯，并且將event和context同時(shí)傳遞給severless_wsgi.py中的handle_reques方法中被啼，那么問(wèn)題來(lái)了，這個(gè)方法是什么棠枉？
這個(gè)方法內(nèi)容好多......看著有點(diǎn)眼暈浓体，但是，我們可以直接發(fā)現(xiàn)這一段代碼：
這一段是什么呢辈讶？這一段實(shí)際上就是將我們拿到的參數(shù)（event和context）進(jìn)行轉(zhuǎn)換命浴，轉(zhuǎn)換之后統(tǒng)一environ中，然后接下來(lái)通過(guò)werkzeug這個(gè)依賴贱除，將這個(gè)內(nèi)容變成request對(duì)象生闲，并且與我們剛才說(shuō)的app對(duì)象一起調(diào)用from_app方法。獲得到反饋：
并且按照API網(wǎng)關(guān)的響應(yīng)集成的格式月幌，將結(jié)果返回碍讯。
此時(shí)此刻，各位看官可能有點(diǎn)想法了扯躺，貌似有一丟丟靈感出現(xiàn)了捉兴，那么我們不妨看一下Flask/Django這些框架的實(shí)現(xiàn)原理：
通過(guò)這個(gè)簡(jiǎn)版的原理圖蝎困，和我剛才說(shuō)的內(nèi)容，我們可以想到倍啥，實(shí)際上正常用的時(shí)候要通過(guò)web_server难衰，進(jìn)入到下一個(gè)環(huán)節(jié)，而我們?cè)坪瘮?shù)更多是一個(gè)函數(shù)逗栽，本不需要啟動(dòng)web server，所以我們就可以直接調(diào)用wsgi_app這個(gè)方法失暂，其中這里的environ就是我們剛才的通過(guò)對(duì)event/context等進(jìn)行處理后的對(duì)象彼宠，start_response可以認(rèn)為是我們的一種特殊的數(shù)據(jù)結(jié)構(gòu)，例如我們的response結(jié)構(gòu)形態(tài)等弟塞。所以凭峡，如果我們自己想要實(shí)現(xiàn)這個(gè)過(guò)程，不使用騰訊云flask-component决记，可以這樣做：
import sys
try:
from urllib import urlencode
except ImportError:
from urllib.parse import urlencode
from flask import Flask
try:
from cStringIO import StringIO
except ImportError:
try:
from StringIO import StringIO
except ImportError:
from io import StringIO
from werkzeug.wrappers import BaseRequest
__version__ = '0.0.4'
def make_environ(event):
environ = {}
for hdr_name, hdr_value in event['headers'].items():
hdr_name = hdr_name.replace('-', '_').upper()
if hdr_name in ['CONTENT_TYPE', 'CONTENT_LENGTH']:
environ[hdr_name] = hdr_value
continue
http_hdr_name = 'HTTP_%s' % hdr_name
environ[http_hdr_name] = hdr_value
apigateway_qs = event['queryStringParameters']
request_qs = event['queryString']
qs = apigateway_qs.copy()
qs.update(request_qs)
body = ''
if 'body' in event:
body = event['body']
environ['REQUEST_METHOD'] = event['httpMethod']
environ['PATH_INFO'] = event['path']
environ['QUERY_STRING'] = urlencode(qs) if qs else ''
environ['REMOTE_ADDR'] = 80
environ['HOST'] = event['headers']['host']
environ['SCRIPT_NAME'] = ''
environ['SERVER_PORT'] = 80
environ['SERVER_PROTOCOL'] = 'HTTP/1.1'
environ['CONTENT_LENGTH'] = str(len(body))
environ['wsgi.url_scheme'] = ''
environ['wsgi.input'] = StringIO(body)
environ['wsgi.version'] = (1, 0)
environ['wsgi.errors'] = sys.stderr
environ['wsgi.multithread'] = False
environ['wsgi.run_once'] = True
environ['wsgi.multiprocess'] = False
BaseRequest(environ)
return environ
class LambdaResponse(object):
def __init__(self):
self.status = None
self.response_headers = None
def start_response(self, status, response_headers, exc_info=None):
self.status = int(status[:3])
self.response_headers = dict(response_headers)
class FlaskLambda(Flask):
def __call__(self, event, context):
if 'httpMethod' not in event:
print('httpMethod not in event')
return super(FlaskLambda, self).__call__(event, context)
response = LambdaResponse()
body = next(self.wsgi_app(
make_environ(event),
response.start_response
))
return {
'statusCode': response.status,
'headers': response.response_headers,
'body': body
}
這樣一個(gè)流程摧冀，就會(huì)變得更加簡(jiǎn)單，清楚系宫。整個(gè)實(shí)現(xiàn)過(guò)程索昂，可以認(rèn)為是對(duì)web server部分進(jìn)行了一種“截?cái)唷被蛘呤恰疤鎿Q”：
這就是對(duì)Flask-Component的基本分析思路，那么按照這個(gè)思路扩借，我們是否可以將Django框架部署上Serverless架構(gòu)呢椒惨？那么Flask和Django有什么區(qū)別呢？我這里的區(qū)別特指的是在運(yùn)行啟動(dòng)過(guò)程中潮罪。
拓展思路：實(shí)現(xiàn)Django-component
仔細(xì)想一下康谆，貌似并沒(méi)有區(qū)別，那么我們是不是可以直接用Flask這個(gè)轉(zhuǎn)換邏輯嫉到，將flask的app替換成django的app呢沃暗？
把：
from flask import Flask
app = Flask(__name__)
替換成：
import os
from django.core.wsgi import get_wsgi_application
os.environ.setdefault('DJANGO_SETTINGS_MODULE', 'mydjango.settings')
application = get_wsgi_application()
是否就能解決問(wèn)題呢？
我們不妨試一下：
建立好Django項(xiàng)目何恶，直接增加index.py：
# -*- coding: utf-8 -*-
import os
import sys
import base64
from werkzeug.datastructures import Headers, MultiDict
from werkzeug.wrappers import Response
from werkzeug.urls import url_encode, url_unquote
from werkzeug.http import HTTP_STATUS_CODES
from werkzeug._compat import BytesIO, string_types, to_bytes, wsgi_encoding_dance
import mydjango.wsgi
TEXT_MIME_TYPES = [
"application/json",
"application/javascript",
"application/xml",
"application/vnd.api+json",
"image/svg+xml",
]
def all_casings(input_string):
if not input_string:
yield ""
else:
first = input_string[:1]
if first.lower() == first.upper():
for sub_casing in all_casings(input_string[1:]):
yield first + sub_casing
else:
for sub_casing in all_casings(input_string[1:]):
yield first.lower() + sub_casing
yield first.upper() + sub_casing
def split_headers(headers):
"""
If there are multiple occurrences of headers, create case-mutated variations
in order to pass them through APIGW. This is a hack that's currently
needed. See: https://github.com/logandk/serverless-wsgi/issues/11
Source: https://github.com/Miserlou/Zappa/blob/master/zappa/middleware.py
"""
new_headers = {}
for key in headers.keys():
values = headers.get_all(key)
if len(values) > 1:
for value, casing in zip(values, all_casings(key)):
new_headers[casing] = value
elif len(values) == 1:
new_headers[key] = values[0]
return new_headers
def group_headers(headers):
new_headers = {}
for key in headers.keys():
new_headers[key] = headers.get_all(key)
return new_headers
def encode_query_string(event):
multi = event.get(u"multiValueQueryStringParameters")
if multi:
return url_encode(MultiDict((i, j) for i in multi for j in multi[i]))
else:
return url_encode(event.get(u"queryString") or {})
def handle_request(application, event, context):
if u"multiValueHeaders" in event:
headers = Headers(event["multiValueHeaders"])
else:
headers = Headers(event["headers"])
strip_stage_path = os.environ.get("STRIP_STAGE_PATH", "").lower().strip() in [
"yes",
"y",
"true",
"t",
"1",
]
if u"apigw.tencentcs.com" in headers.get(u"Host", u"") and not strip_stage_path:
script_name = "/{}".format(event["requestContext"].get(u"stage", ""))
else:
script_name = ""
path_info = event["path"]
base_path = os.environ.get("API_GATEWAY_BASE_PATH")
if base_path:
script_name = "/" + base_path
if path_info.startswith(script_name):
path_info = path_info[len(script_name) :] or "/"
if u"body" in event:
body = event[u"body"] or ""
else:
body = ""
if event.get("isBase64Encoded", False):
body = base64.b64decode(body)
if isinstance(body, string_types):
body = to_bytes(body, charset="utf-8")
environ = {
"CONTENT_LENGTH": str(len(body)),
"CONTENT_TYPE": headers.get(u"Content-Type", ""),
"PATH_INFO": url_unquote(path_info),
"QUERY_STRING": encode_query_string(event),
"REMOTE_ADDR": event["requestContext"]
.get(u"identity", {})
.get(u"sourceIp", ""),
"REMOTE_USER": event["requestContext"]
.get(u"authorizer", {})
.get(u"principalId", ""),
"REQUEST_METHOD": event["httpMethod"],
"SCRIPT_NAME": script_name,
"SERVER_NAME": headers.get(u"Host", "lambda"),
"SERVER_PORT": headers.get(u"X-Forwarded-Port", "80"),
"SERVER_PROTOCOL": "HTTP/1.1",
"wsgi.errors": sys.stderr,
"wsgi.input": BytesIO(body),
"wsgi.multiprocess": False,
"wsgi.multithread": False,
"wsgi.run_once": False,
"wsgi.url_scheme": headers.get(u"X-Forwarded-Proto", "http"),
"wsgi.version": (1, 0),
"serverless.authorizer": event["requestContext"].get(u"authorizer"),
"serverless.event": event,
"serverless.context": context,
# TODO: Deprecate the following entries, as they do not comply with the WSGI
# spec. For custom variables, the spec says:
#
# Finally, the environ dictionary may also contain server-defined variables.
# These variables should be named using only lower-case letters, numbers, dots,
# and underscores, and should be prefixed with a name that is unique to the
# defining server or gateway.
"API_GATEWAY_AUTHORIZER": event["requestContext"].get(u"authorizer"),
"event": event,
"context": context,
}
for key, value in environ.items():
if isinstance(value, string_types):
environ[key] = wsgi_encoding_dance(value)
for key, value in headers.items():
key = "HTTP_" + key.upper().replace("-", "_")
if key not in ("HTTP_CONTENT_TYPE", "HTTP_CONTENT_LENGTH"):
environ[key] = value
response = Response.from_app(application, environ)
returndict = {u"statusCode": response.status_code}
if u"multiValueHeaders" in event:
returndict["multiValueHeaders"] = group_headers(response.headers)
else:
returndict["headers"] = split_headers(response.headers)
if event.get("requestContext").get("elb"):
# If the request comes from ALB we need to add a status description
returndict["statusDescription"] = u"%d %s" % (
response.status_code,
HTTP_STATUS_CODES[response.status_code],
)
if response.data:
mimetype = response.mimetype or "text/plain"
if (
mimetype.startswith("text/") or mimetype in TEXT_MIME_TYPES
) and not response.headers.get("Content-Encoding", ""):
returndict["body"] = response.get_data(as_text=True)
returndict["isBase64Encoded"] = False
else:
returndict["body"] = base64.b64encode(response.data).decode("utf-8")
returndict["isBase64Encoded"] = True
return returndict
def main_handler(event, context):
return handle_request(mydjango.wsgi.application, event, context)
然后我們部署到函數(shù)上孽锥，看一下效果：
函數(shù)信息：
from django.shortcuts import render
from django.http import HttpResponse
from django.views.decorators.csrf import csrf_exempt
# Create your views here.
@csrf_exempt
def hello(request):
if request.method == "POST":
return HttpResponse("Hello world ! " + request.POST.get("name"))
if request.method == "GET":
return HttpResponse("Hello world ! " + request.GET.get("name"))
通過(guò)部署完成，并綁定apigw觸發(fā)器细层，然后在postman中進(jìn)行測(cè)試：
get：
post：
可以看到忱叭，通過(guò)我們對(duì)運(yùn)行原理的基本剖析和對(duì)django的改造，我們已經(jīng)通過(guò)增加一個(gè)文件和相關(guān)依賴的方法今艺，實(shí)現(xiàn)了Django上Serverless的過(guò)程韵丑。
接下來(lái)，我們看一下虚缎，如何將這個(gè)代碼寫成一個(gè)Component：
首先Clone下來(lái)Flask-Component的代碼：
然后撵彻，我們按照Django的部分模式進(jìn)行修改：
第一部分钓株，是我們可能會(huì)依賴的一個(gè)依賴包，以及我們剛才放入的index.py文件陌僵。在用戶調(diào)用這個(gè)Component的時(shí)候轴合，我們會(huì)把這兩個(gè)文件，放入用戶的代碼中碗短，一并上傳受葛。
第二部分是Serverless.js部分，這里的一個(gè)基本格式：
const { Component } = require('@serverless/core')
class TencentDjango extends Component {
async default(inputs = {}) {
}
async remove(inputs = {}) {
}
}
module.exports = TencentDjango
用戶在執(zhí)行sls的時(shí)候偎谁，會(huì)默認(rèn)調(diào)用default的方法总滩，在執(zhí)行sls remove的時(shí)候會(huì)調(diào)用remove的方法，所以可以認(rèn)default的內(nèi)容是部署巡雨，而remove的內(nèi)容是移除闰渔。
部署這里主要流程也蠻簡(jiǎn)單的，首先將文件進(jìn)行復(fù)制和處理铐望，然后直接調(diào)用云函數(shù)的組件冈涧，通過(guò)函數(shù)中的include參數(shù)將這些文件額外加入，再通過(guò)調(diào)用apigw的組件來(lái)進(jìn)網(wǎng)關(guān)的管理正蛙，而用戶寫的yaml中inpust的內(nèi)容督弓，會(huì)在inputs中獲取，我們要做的就是對(duì)應(yīng)的傳給不同的組件：
當(dāng)然除了這兩部分對(duì)應(yīng)放過(guò)去乒验，上面的region等一些信息也要對(duì)應(yīng)的進(jìn)行處理咽筋。而調(diào)用底層組件方法也很簡(jiǎn)單：
const tencentCloudFunction = await this.load('@serverless/tencent-scf'
const tencentCloudFunctionOutputs = await tencentCloudFunction(inputs)
處理好這里之后，只需要修改一下package.json和readme就可以了徊件。
目前奸攻，我已經(jīng)完成了開(kāi)源：https://github.com/gosls/tencent-django
也在NPM上進(jìn)行了發(fā)布：https://www.npmjs.com/package/@gosls/tencent-django
在使用的時(shí)候，只需要引入這個(gè)Component就好：
DjangoTest:
component: '@serverless/tencent-django'
inputs:
region: ap-guangzhou
functionName: DjangoFunctionTest
djangoProjectName: mydjango
code: ./
functionConf:
timeout: 10
memorySize: 256
environment:
variables:
TEST: vale
vpcConfig:
subnetId: ''
vpcId: ''
apigatewayConf:
protocols:
- http
environment: release
至此虱痕，完成了Django Component的開(kāi)發(fā)和測(cè)試睹耐。
