Ndtyjky

I have a Python Flask app. When I run it from PowerShell, I can see the stream of output coming from calls to functions like print() and logging.info() throughout my code.

When I point IIS to my app and have it run through FastCGI with a web.config file, where does that output stream go? How can I capture it to a log file?

There are 3 kinds of log files when you use FastCGI/WSGI.

Let's name them:

• WSGI log
  
  
  
  
  • File name from the example below: wsgi_myapp.log
  
  
  • gets the stream (StdOut, StdErr) from wsgi main script
  
  
  • For example when you publish new version of your page to the server, wsgi will restart and the messages about restarting goes there.
  
  
  • Another example is when your application encounters uncaught error, it saves the traceback into this file
  
  
  
  


• App log
  
  
  
  
  • File name from the example below: myapp.log
  
  
  • Here goes everything what you want to log throught app.logger.LEVEL("..."), considering the right LEVEL is set on the logger as well as on the handler
  
  
  
  


• HTTP requests log
  
  
  
  
  • Not a part of my code example below
  
  
  • The logs of the requests received by your HTTP server
  
  
  • You can change the location and behavior of this log from within IIS Logging settings of the web page
  
  
  • you can see these during the development alongside your own prints and log messages
  
  
  • Example from flask: "[2019-01-12 21:08:00,748] INFO in _internal: 127.0.0.1 - - [12/Jan/2019 21:08:00] "GET /static/js/jquery-3.3.1.min.js HTTP/1.1" 304 -
    
  
  
  • Example from ISS: 2019-01-12 20:42:41 10.175.214.88 GET /static/js/jquery-ui.min.js 80 ****USER**** ****IP**** Mozilla/5.0+(Windows+NT+10.0;+WOW64)+AppleWebKit/537.36+(KHTML,+like+Gecko)+Chrome/70.0.3538.110+Safari/537.36 http://yourweb.com/smthing 304 0 0 1875
    
  
  
  
  

See this example:

from flask import Flask

from logging.config import dictConfig



dictConfig({

    'version': 1,

    'formatters': {'default': {

        'format': '[%(asctime)s] %(levelname)s in %(module)s: %(message)s',

    }},

    'handlers': {

        'wsgi': {

            'class': 'logging.StreamHandler',

            'formatter': 'default'

        },

        'custom_handler': {

            'class': 'logging.FileHandler',

            'formatter': 'default',

            'filename': r'C:inetpubwwwrootmyapplogsmyapp.log'

        }

    },

    'root': {

        'level': 'INFO',

        'handlers': ['wsgi', 'custom_handler']

    }

})



app = Flask(__name__)



# other imports using logger should go here

# from a import b

# ...

and the web.config file:

<configuration>

  <system.webServer>

    <handlers>

      <remove name="Python FastCGI" />

      <add name="Python FastCGI" path="*" verb="*" modules="FastCgiModule" scriptProcessor="E:Python362_64python.exe|E:Python362_64Libsite-packageswfastcgi.py" resourceType="Unspecified" requireAccess="Script" />

    </handlers>

        <urlCompression doStaticCompression="true" doDynamicCompression="true" />

  </system.webServer>

  <appSettings>

    <!-- Required settings -->

    <add key="WSGI_HANDLER" value="myapp.app" />

    <add key="PYTHONPATH" value="C:inetpubwwwrootmyapp" />

    <add key="SCRIPT_NAME" value="/myapp" />

    <add key="WSGI_LOG" value="C:inetpubwwwrootmyapplogswsgi_myapp.log" />

    <add key="WSGI_RESTART_FILE_REGEX" value=".*((.py)|(.config))$" />

  </appSettings>

</configuration>