mod_wsgi importError

[Tierprot B.]

Good day, im trying to deploy a server on CentOs7 in combination Flask+Apache 2.4+mod_wsgi 4.5.5. Mod_wsgi was compiled with python 3.5.2 and test-run from manual works fine. However when i tried to connect mine app i failed so i reduced tests to only Apache+mod_wsgi stack and found that somehow import of python modules isnt working. The simplest test ive run is -  ive got folder with wsgi file and some function deployed in the same folder.


insides of simple_app.wsgi:
---------------------------
import sys, os
sys.path.insert(0,os.getcwd())

import add

def application(environ, start_response):
    status = '200 OK'
    output = add.echo()

    response_headers = [('Content-type', 'text/plain'),
                        ('Content-Length', str(len(output)))]
    start_response(status, response_headers)
    return [output]

-------------------------

insides of add.py:
-------------------------
def echo():
     return b'module import is fine'
-------------------------

Apache VirtualHost config:
-------------------------
<VirtualHost *:80>
      ServerName www.example.com
      DocumentRoot /var/www/html
      WSGIScriptAlias /test /var/www/wsgi-scripts/simple_app.wsgi
     
      <Directory /var/www/wsgi-scripts>
          Require all granted
      </Directory>
 </VirtualHost>

Apache logs are telling:
...
[wsgi:error] [pid 11717] [client 83.220.186.194:56534] ImportError: no module named 'add'
...

If i will leave the same Apache config, remove importing stuff from simple_app.wsgi and as a result will return some byte string, like in this code:

def application(environ, start_response):
    status = '200 OK'
    output = b'Hello, World!'

    response_headers = [('Content-type', 'text/plain'),
                        ('Content-Length', str(len(output)))]
    start_response(status, response_headers)
    return [output]

everything will work just fine without errors and by opening www.example.com/test i will see

"Hello, World!"

Since im totally newbie in Apache/mod_wsgi stuff all suggestions are welcome!

[Graham Dumpleton]

The current working directory of the process will not be where you source code is located, thus using os.getcwd() will not do what you want.

Use a configuration of:

    WSGIDaemonProcess myapp home=/var/www/wsgi-scripts

    WSGIScriptAlias /test /var/www/wsgi-scripts/simple_app.wsgi process-group=myapp application-group=%{GLOBAL}

and delete the modification of sys.path from the WSGI script file.

The WSGIDaemonProcess directive sets you up for using daemon mode, which is better than embedded mode.

    http://blog.dscpl.com.au/2012/10/why-are-you-using-embedded-mode-of.html

The ‘home’ option to WSGIDaemonProcess changes the current working directory to be the directory where your WSGI script is and should also result in that directory being in the module search path.

If my memory is fuzzy, and that directory isn’t in module search path, also add to WSGIDaemonProcess the option:

    python-path=/var/www/wsgi-scripts

Graham

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[Tierprot B.]

Thanks for the fast reply! I did what you`ve wrote and yay it worked! Now i wondering how can i tell to mod_wsgi two things - a) that wsgi file itself lies in /var/www/wsgi-scripts and b) that it should include python files from outside directory, for example home/user/flask_stuff_files ?

[Graham Dumpleton]

On 21 Aug 2016, at 8:35 PM, Tierprot B. <tier...@gmail.com> wrote:

Thanks for the fast reply! I did what you`ve wrote and yay it worked! Now i wondering how can i tell to mod_wsgi two things - a) that wsgi file itself lies in /var/www/wsgi-scripts and

That is what WSGIScriptAlias is doing in giving it the path to the WSGI script file. If you mean something different you need to be clearer.

b) that it should include python files from outside directory, for example home/user/flask_stuff_files ?

If you are talking about other places to look for Python modules to import, that is what the python-path option for WSGIDaemonProcess that I mentioned is for.

Graham

[Tierprot B.]

That is what WSGIScriptAlias is doing in giving it the path to the WSGI script file. If you mean something different you need to be clearer.

b) that it should include python files from outside directory, for example home/user/flask_stuff_files ?

If you are talking about other places to look for Python modules to import, that is what the python-path option for WSGIDaemonProcess that I mentioned is for.

Graham

Ok, ive got python modules which i try to import located at home/user/flask_stuff_files, mine wsgi file is in /var/www/wsgi-scripts, now to the code:

apache-wsgi config:
----------------------------

<VirtualHost *:80>
      ServerName www.example.com
      DocumentRoot /var/www/html

      WSGIDaemonProcess home=/var/www/wsgi-scripts python-path=home/user/flask_stuff_files

      WSGIScriptAlias /test /var/www/wsgi-scripts/simple_app.wsgi
     
      <Directory /var/www/wsgi-scripts>
          Require all granted
      </Directory>
 </VirtualHost>

-------------------------

simple_app.wsgi:
----------------------------------
import server_handle

def application(environ, start_response):
    status = '200 OK'
    output = b'Hello, World!'

    response_headers = [('Content-type', 'text/plain'),
                        ('Content-Length', str(len(output)))]
    start_response(status, response_headers)
    return [output]

------------------------------------

server_handle.py module is located at /home/user/flask_stuff_files

on trying www.example.com/test Apache spits with error ImportError: no module named 'server_handle' 

adding of code like:

import sys
sys.path.insert(0,'/home/user/flask_stuff_files')

dont solve the problem too (do you know why, btw?)

Theres something i didn`t properly understood, so sorry for annoying and dumb questions :)

[Graham Dumpleton]

Your code will be running as the Apache user. Your home directory would have restrictive permissions on it such that not everyone can access files out of it.

The quickest solution would be to set the process/group that the mod_wsgi daemon process runs as.

    WSGIDaemonProcess home=/var/www/wsgi-scripts python-path=/home/user/flask_stuff_files user=xxx group=yyy

Replace xxx with your user name and yyy with the group name, likely same as xxx.

Thi presumes the issue isn’t as simple as you having left off the leading slash on the path to the python-path option as your snippet showed.

Graham

[Tierprot B.]

Aha! Thanks! Addition of proper user and group options to WSGIDaemonProcess solved the ImportError! The last question i have might be not related to mod_wsgi directly, but still.

I have a Flask app, purpose of which to be able to upload files provided by user, do some math and return result on a new page. Simplified code looks like this:

...

@app.route('/'):

def index()

     return render_template('index.html')

@app.route('/analysis', methods=['POST'])

def upload():

     uploaded_files = request.files.getlist('files')
     ...

     for file in uploaded_files:
           ...

     return render_template('analysis.html')

...

The folder with static files which Flask renders is:

home/user/flask_stuff_files/templates

in Apache ive corrected document root folder and added directory with static files:

apache-wsgi config:
----------------------------

<VirtualHost *:80>
      ServerName www.example.com

      DocumentRoot /home/user/flask_stuff_files/templates
      WSGIDaemonProcess home=/var/www/wsgi-scripts python-path=/home/user/flask_stuff_files user=user group=user
      WSGIScriptAlias /test /var/www/wsgi-scripts/simple_app.wsgi process-group=app application-group=%{GLOBAL}

     
      <Directory /var/www/wsgi-scripts>
          Require all granted
      </Directory>

      <Directory /home/user/flask_stuff_files>

          WSGIProcessGroup app

          WSGIApplicationGroup %{GLOBAL}

          Require all granted
      </Directory>

      <Directory /home/user/flask_stuff_files/templates>

          WSGIProcessGroup app

          WSGIApplicationGroup %{GLOBAL}

          Require all granted
      </Directory>

 </VirtualHost>

So, www.example.com/test - it renders main page as intended, but when i select files and submit them via POST request ive got a forbidden access with error_log : Permission denied [...] : acces to /analysis denied (filesystempath '/home/user/flask_stuff_files') because search permissions are missing on a component of the path, referer: www.example.com/test.

For the test, i set permissions of the folder /home/user/flask_stuff_files to the drwxrwxrwx, it belongs to user user.

So, could you share your thoughts on what is wrong here?

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[Graham Dumpleton]

On 22 Aug 2016, at 8:16 AM, Tierprot B. <tier...@gmail.com> wrote:

Aha! Thanks! Addition of proper user and group options to WSGIDaemonProcess solved the ImportError! The last question i have might be not related to mod_wsgi directly, but still.

I have a Flask app, purpose of which to be able to upload files provided by user, do some math and return result on a new page. Simplified code looks like this:

...

@app.route('/'):

def index()

     return render_template('index.html')

@app.route('/analysis', methods=['POST'])

def upload():

     uploaded_files = request.files.getlist('files')
     ...

     for file in uploaded_files:
           ...

     return render_template('analysis.html')

...

The folder with static files which Flask renders is:

home/user/flask_stuff_files/templates

in Apache ive corrected document root folder and added directory with static files:

apache-wsgi config:
----------------------------
<VirtualHost *:80>
      ServerName www.example.com
      DocumentRoot /home/user/flask_stuff_files/templates

What are you trying to have happen by adding this?

The Apache user would need access to that directory and once agains the permissions on the directories are such that that can’t happen. Changing user for mod_wsgi daemon process group only affects access to Python code, not static files Apache tries to serve up.

In general this is why is better not to have anything for your application under your home directory. Better under separate directory for project under /var/www.

      WSGIDaemonProcess home=/var/www/wsgi-scripts python-path=/home/user/flask_stuff_files user=user group=user
      WSGIScriptAlias /test /var/www/wsgi-scripts/simple_app.wsgi process-group=app application-group=%{GLOBAL}
     
      <Directory /var/www/wsgi-scripts>
          Require all granted
      </Directory>

      <Directory /home/user/flask_stuff_files>

          WSGIProcessGroup app

          WSGIApplicationGroup %{GLOBAL}

          Require all granted
      </Directory>

May not need this entry for /home/user/flask_stuff_files.

      <Directory /home/user/flask_stuff_files/templates>

          WSGIProcessGroup app

          WSGIApplicationGroup %{GLOBAL}

          Require all granted
      </Directory>

May not need this entry for /home/user/flask_stuff_files/templates. Depends on answer about DocumentRoot.

The Directory block and access grants is only needed for where the WSGI script file is located.

The WSGIScriptAlias already specifies process-group and application-group so the WSGIProcessGroup and WSGIApplicationGroup not needed either.

 </VirtualHost>

So, www.example.com/test - it renders main page as intended, but when i select files and submit them via POST request ive got a forbidden access with error_log : Permission denied [...] : acces to /analysis denied (filesystempath '/home/user/flask_stuff_files') because search permissions are missing on a component of the path, referer: www.example.com/test.

For the test, i set permissions of the folder /home/user/flask_stuff_files to the drwxrwxrwx, it belongs to user user.

So, could you share your thoughts on what is wrong here?

Graham

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[Tierprot B.]

Hmm and now im more confused, i copied server files from /home/user/flask_stuff_files to the new directory /var/www/flask_stuff_files and corrected Apache conf, now it looks like:

apache-wsgi config:
----------------------------

<VirtualHost *:80>
      ServerName www.example.com

      DocumentRoot /var/www/flask_stuff_files/templates
      WSGIDaemonProcess home=/var/www/wsgi-scripts python-path=/var/www/flask_stuff_files user=user group=user

      WSGIScriptAlias /test /var/www/wsgi-scripts/simple_app.wsgi process-group=app application-group=%{GLOBAL}
     
      <Directory /var/www/wsgi-scripts>
          Require all granted
      </Directory>

 </VirtualHost>

 

Still main page www.example.com/test renders ok, but on files submission i get error File does not exist: /var/www/flask_stuff_files/templates/analysis, referer: http://www.example.com/test

[Graham Dumpleton]

And does /var/www/flask_stuff_files/templates/analysis exist? Does it have to be a directory or a file? For uploads those directories will need to be writable to Apache user.

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