问题描述
在成功的部署Python flask应用到App Service (Windows)后，如果需要把当前项目（如：hiflask）作为一个子项目(子站点），把web.config文件从wwwroot中移动到项目文件夹中。访问时，确遇见了404 Not Found的错误。
查看flask项目的启动日志，可以看见项目启动已经成功。但是为什么请求一直都是404的问题呢？
2021-09-10 05:29:58.224796: wfastcgi.py will restart when files in D:\home\site\wwwroot\hiflask\ are changed: .*((\.py)|(\.config))$
2021-09-10 05:29:58.240445: wfastcgi.py 3.0.0
问题解决
在搜索 flask return 404问题后，发现是因为 URL前缀（prefixed ）的问题。因为当前的flask应用访问路径不再是根目录（/），而是(/hiflask)。 所以需要 flask项目中使用 中间件 来处理 url前缀的问题。
原文内容为：https://stackoverflow.com/questions/18967441/add-a-prefix-to-all-flask-routes/36033627#36033627
You have to do is to write a middleware to make the following changes:
- modify
PATH_INFO to handle the prefixed url. - modify
SCRIPT_NAME to generate the prefixed url.
Like this:
class PrefixMiddleware(object): def __init__(self, app, prefix=''): self.app = app self.prefix = prefix def __call__(self, environ, start_response): if environ['PATH_INFO'].startswith(self.prefix): environ['PATH_INFO'] = environ['PATH_INFO'][len(self.prefix):] environ['SCRIPT_NAME'] = self.prefix return self.app(environ, start_response) else: start_response('404', [('Content-Type', 'text/plain')]) return ["This url does not belong to the app.".encode()]
Wrap your app with the middleware, like this:
from flask import Flask, url_for app = Flask(__name__) app.debug = True app.wsgi_app = PrefixMiddleware(app.wsgi_app, prefix='/foo') @app.route('/bar') def bar(): return "The URL for this page is {}".format(url_for('bar')) if __name__ == '__main__': app.run('0.0.0.0', 9010)
Visit http://localhost:9010/foo/bar,
You will get the right result: The URL for this page is /foo/bar
而在App Service中的解决方式就是添加了 PrefixMiddleware，并指定prefix为 /hiflask 。 附上完成的hiflask/app.py 代码和web.config内容。
hiflask/app.py
from flask import Flask
from datetime import datetime
from flask import render_template
import re
class PrefixMiddleware(object):
def __init__(self, app, prefix=''):
self.app = app
self.prefix = prefix
def __call__(self, environ, start_response):
if environ['PATH_INFO'].startswith(self.prefix):
environ['PATH_INFO'] = environ['PATH_INFO'][len(self.prefix):]
environ['SCRIPT_NAME'] = self.prefix
return self.app(environ, start_response)
else:
start_response('404', [('Content-Type', 'text/plain')])
return ["This url does not belong to the app.".encode()]
#if __name__ =="__name__"
app = Flask(__name__)
app.debug = True
app.wsgi_app = PrefixMiddleware(app.wsgi_app, prefix='/hiflask')
# @app.route("/")
# def home():
# return "Hello, Flask!"
print("flask applicaiton started and running..." +datetime.now().strftime("%m/%d/%Y, %H:%M:%S"))
# Replace the existing home function with the one below
@app.route("/")
def home():
return render_template("home.html")
# New functions
@app.route("/about/")
def about():
return render_template("about.html")
@app.route("/contact/")
def contact():
return render_template("contact.html")
@app.route("/hello/")
@app.route("/hello/<name>")
def hello_there(name = None):
return render_template(
"hello_there.html",
name=name,
date=datetime.now()
)
@app.route("/api/data")
def get_data():
return app.send_static_file("data.json")
if __name__ == '__main__':
app.run(debug=True)
hiflask/web.config
<?xml version="1.0" encoding="utf-8"?>
<configuration>
<appSettings>
<add key="WSGI_HANDLER" value="app.app"/>
<add key="PYTHONPATH" value="D:\home\site\wwwroot\hiflask"/>
<add key="WSGI_LOG" value="D:\home\site\wwwroot\hiflask\hiflasklogs.log"/>
</appSettings>
<system.webServer>
<handlers>
<add name="PythonHandler" path="*" verb="*" modules="FastCgiModule" scriptProcessor="D:\home\python364x64\python.exe|D:\home\python364x64\wfastcgi.py" resourceType="Unspecified" requireAccess="Script"/>
</handlers>
</system.webServer>
</configuration>
最终效果(作为子项目部署完成成功，所以一个app service就可以部署多个站点)
提醒一点：App Service中如果要部署多站点，需要在Configration 中配置 Virtual Applications。
参考资料：
https://stackoverflow.com/questions/18967441/add-a-prefix-to-all-flask-routes/36033627#36033627
当在复杂的环境中面临问题，格物之道需：浊而静之徐清，安以动之徐生。 云中，恰是如此!
